Horticultural Science – a US perspective

A study tour in the Southern USA

19th – 25th April 2015

Gracie Barrett (RHS Horticultural Scientist)

Preface

Lament of the UK Horticultural Scientist

There are many branches of science from astrophysics to ecology and all have played their part in changing the world for the better. Sadly, the world of science is not exempt from politics and while all branches of science may be theoretically equal, some are definitely more equal than others. We all love the hopeful buzz of a good science break-through - from cancer cures to dark matter – yet how often do we hear about the wonders of horticultural science? The discovery of a new bio-control for aphids or the development of a new higher yielding tomato variety? Ok, perhaps it’s not as sexy as the discovery of the Higgs-Boson particle but I would argue that advances in agricultural and horticultural science have been some of the most significant in human history. The modern agricultural revolution has freed the first world from hunger allowing populations to grow, innovate and take the time to contemplate the nature of their existence.

The simple truth is that our very way of life depends on the innovation and skill of those working to safe guard plants. Plant breeders, geneticists, soil scientists, botanists, pathologists, entomologists and taxonomists; all play their part in protecting and improving the plants we depend on. That packet of tomatoes or bag of salad sitting so conveniently on the supermarket shelf represents the culmination of decades of horticultural research. Yet somehow we’ve all become a little complacent about plants and our ability to grow endless amounts of them.

Perhaps this is why in the last two decades there has been a serious lack of investment in UK horticultural science. While there are a few notable exceptions, when it comes to world class horticultural research the UK is struggling. There is not one university in the UK which offers a Bachelor’s degree in horticulture. As highlighted by the RHS campaign ‘Horticultural Matters’ the idea of a career in horticulture is perceived by many of our young people as a last resort for the academically challenged. This represents a serious problem for all UK citizens because we are entering a time in our history when we have never needed skilled horticulturalists more. Our technological successes have led to a rapidly expanding global population driving a new wave of challenges; climate change, novel pests and diseases, pollution, degraded soils….. These problems all have the potential to erode the sense of security we now take for granted in the developed world. These problems aren’t insurmountable, but the innovative solutions required won’t materialise without research …and for research you absolutely need scientists.

Contents

Introduction ....................................................................................................................... 1

Objectives of the US study tour ......................................................................................... 2

Itinerary for the tour ........................................................................................................... 3

Part I Horticultural science in North Carolina .................................................................. 4

Introduction to North Carolina and North Carolina State University ................................... 4

19th April 2015 .................................................................................................................. .5

20th April 2015 ................................................................................................................... 7

21st April 2015 ................................................................................................................. 15

Summary and Conclusions of visit to North Carolina ...................................................... 20

Part II Horticultural Science in Arkansas ....................................................................... 21

Introduction to Arkansas and the University of Arkansas ................................................ 21

22nd April 2015 ................................................................................................................ 21

23nd April 2015 ................................................................................................................ 23

24th April 2015 ................................................................................................................. 27

25th April 2015 ................................................................................................................. 35

Summary and conclusions of visit to Arkansas ............................................................... 39

Final Summary ................................................................................................................. 39

Summary of Expenditure ................................................................................................. 40

Acknowledgements ......................................................................................................... 41

References and useful links ............................................................................................ 42

Appendix .......................................................................................................................... 44

1

Introduction

I was employed as a trainee horticultural scientist at RHS Wisley in November 2012 as part of a jointly funded RHS and Agricultural and Horticultural Development board (AHDB) fellowship project entitled:

“Sustainable resource use in horticulture: a systems approach to delivering high quality plants grown in sustainable substrates, with efficient water use, and novel nutrient sources”

It’s a five year project and I’m being mentored by a group of scientists and industry professionals who are imparting their skills and knowledge to the project. These include Paul Alexander who is head of Horticultural and Environmental science at the RHS and Neil Bragg, who is a director at Bulrush Horticulture Ltd., a growing media manufacturer. With their guidance I’ve been conducting research on a range of peat-free and peat-reduced container growing media, addressing the reliance of the UK horticultural industry on peat. The aim of the work has been to better understand how peat alternative materials such as coir, bark and green waste compost can be combined to support high quality plant growth for both professional and amateur growers.

Alongside the research aim of the project, the other key objective is a training and career development one; to provide me with the skills, knowledge and networks to establish myself as a professional horticultural scientist. As highlighted in the foreword, the UK Horticultural Industry is facing a knowledge and skills gap. In the last two decades there has been a serious lack of investment meaning few early career scientists like me are choosing to work in the sector. The fellowship project is then, an attempt to address this; by giving a relatively junior scientist, a launch-pad into the Horticultural sector.

When I started at Wisley in 2012 I was completely new to the world of applied horticultural research. So I began by carrying out a review of the existing published literature on soilless container growing media. What I noticed early on was that in the last 10 years, there had been relatively few articles on this topic by UK researchers. In fact, many of the most useful scientific papers I read seemed to have been authored by US based researchers. Several institutions, in particular North Carolina State University and Arkansas University, seemed to crop up again and again (excuse the pun). In June 2013 I was lucky enough to attend my first international horticultural conference, a fantastic opportunity to meet other researchers and get myself up to speed on the latest innovations in container growing media. What struck me was just how many US delegates were present. These weren’t just scientists but also PhD and Master’s students and without exception these students were good…….very good. Not only were they doing high quality science but could communicate it eloquently. It was clear to both myself and my other UK colleagues (there were only 5 of us present and no students) that the US was doing something right. The aforementioned Paul and Neil have over the years, had an opportunity to get to know some of these US scientists - email addresses and casual invitations had been exchanged. Thus an idea was formed and the plan for a fellowship study tour to the USA began to take shape.

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A shared goal – container growing media research and the search for new materials

It’s perhaps important here to provide some background about why we (Paul, Neil and I) were so interested in visiting the USA and particularly North Carolina State University (NCSU) and the University of Arkansas (UA).

In the UK, most of the growing media we use in plant containers are peat-based. Peat is very effective at holding both and air and water so makes an excellent matrix for root growth. It’s also relatively cheap and in plentiful supply thus has come to dominate the UK ornamental plant industry. The problem is that in the last 20 years, the extraction of peat from bogs has become increasing controversial because of its high environmental cost. As a result the UK government is now pushing for all growing media to become peat-free. This presents a significant challenge for researchers, growers and growing media manufacturers – to identify suitable alternatives and incorporate them into existing plant production systems. Interestingly the US ornamental sector is facing the same basic challenge, although the drivers bringing about change are different – I’ll explain.

In the southern and eastern US, container growing media has been largely based on pine bark rather than peat. Peat is not locally available and too expensive to transport the massive distances from source to nursery. Pine bark, the by-product of the lumber industry was until quite recently a plentiful, cheap raw material for growing media with many useful properties for plant growth. Like peat in the UK, it has come to dominate the US ornamental sector. However, the global down-turn has seen the lumber industry shrink and transport costs rise. In conjunction with this, a new market has emerged for pine bark – the energy market - which has seen competition for this resource rise and thus prices increase. The horticultural industry in the US finds itself with the same fundamental challenge as the UK; the need to find new, sustainable raw materials for growing media. What’s useful for us here in the UK is that US scientists seem to be further along in this search for alternatives and have in recent years published prolifically on the subject of container growing media. Not only have they documented successful trials with a range of organic materials (particularly novel materials that would otherwise end up in land-fill), but also published practical approaches to assessing the suitability of different materials.

Objectives of the US study tour

1. Acquire knowledge that will lead to innovation in the approach I take to my research on sustainable growing media here at RHS Wisley, particularly plant nutrition in peat-free formulations.

2. Open communications and build long-term relationships with world class horticultural researchers vital to my development as a horticultural scientist.

3. Promote UK horticultural research encouraging communication and collaboration between UK and US horticultural institutions who are conducting authoritative, high quality horticultural science.

4. Learn from the way in which horticultural science drives innovation in US growing

practices and how this science is communicated to both industry and the gardening community.

5. On return, communicate findings of the trip to the UK horticultural industry through presentations, articles and social media.

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Itinerary for the tour

Date

Location & venue(s)

Activity

Sat. 18th - Sun. 19th April

London to Rayleigh in North Carolina (NC).

Sun. 19th April Rayleigh, NC.

Tour of the city, university campus & research farms Visit to NC State farmers market Dinner with horticultural department staff

Mon. 20th April

North Carolina State University (NCSU)

Tour of the JC Raulston Arboretum Tour of the horticultural field laboratory & substrates

processing & research centre Tour of horticultural growing media laboratory & glass

houses Growing media group seminar (presentations by UK & US

researchers) Departmental seminar – ‘Wettability of horticultural

substrates’ Dinner with growing media group scientists

Tue. 21st April

NCSU Tour growing media manufacturers: AM: Pacific organics, PM: Old Castle lawn and garden.

Wed. 22nd April

Travel & the city of Fayetteville

Internal flights from Rayleigh (NC) to Fayetteville, Arkansas (ARK).

Tour of Fayetteville & down-town area

Thu. 23rd April

The University of Arkansas (UA)

Tour of the UA campus Tour of the department of horticulture including labs,

glasshouses and growth rooms Departmental seminar: Paul, Gracie & Neil give

presentations followed by discussion Meeting with the director of International programs Discussion about Horticultural science education at the

UA & tour of online learning resources. Dinner with horticulture department head

Fri. 24th April

The UA

AM: Tour of experimental research and extension Centre PM: Visit to Greenleaf and Ozark All Seasons nurseries Dinner with hosts

Sat. 25th Tour of horticultural attractions in & around Fayetteville

AM: Tour Compton gardens PM: Tour of Crystal Bridges Museum of American Art and

it’s gardens

Sun. 26th to Mon. 27th April

Travel Arkansas to London

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PART I: HORTICULTURAL SCIENCE IN NORTH CAROLINA

An introduction to North Carolina (NC) and North Carolina State University (NCSU)

Map 1 The location of North Carolina in relation to the rest of the USA. The city of Rayleigh is marked with a star

It’s a 13 hour trip from London to NC which is situated on the south eastern coast of the United States (map 1). Our destination was the state capital Rayleigh, a bustling and prosperous city which recently featured on the Forbes list as the no. 1 place for business and careers in the US. It is also part of the NC ‘research triangle’, one of the most successful research parks and major centres for high-tech and biotech research in the US. NCSU is an integral part of the city sitting at its heart and being its third largest employer.

The university was founded in 1887 as one of the many state colleges across the US to arise in the mid to late 1800’s as ‘Land-grant institutions’. These institutions were publically funded through the sale of state owned land and focused on the teaching of practical skills in subjects such as agriculture, science and engineering. They were driven by an admirable philosophy; that colleges should not be reserved for the privileged few and that the children of farmers, mechanics and other workers should have access to the benefits and opportunities of higher education. Like most land-grant colleges across the US, NCSU became a large publically funded university; in fact it’s a leviathan by UK standards with at present more than 34,000 students and 8,000 staff.

Our visit was to the department of horticultural science, but before I talk more about this I’ll explain how the department sits within the structure of the university. The university is made up of colleges, horticulture is one of 16 departments which belongs to the college of agricultural and life sciences.

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This college has three branches:

1. Office of academic programs: Deals with teaching students 2. NC Agricultural research service: Deals with research 3. NC Cooperative extension service: Deals with education programs which are extended

to farmers and growers throughout the state. The role of this department is to translate research findings into practical advice for growers.

These three branches run throughout all departments belonging to the college including the department of horticulture.

19th April 2015 A tour of Rayleigh, the University campus, research farms and NC State farmers market.

It took us an exhausting 13 hours of travelling to reach Rayleigh, but we were all refreshed after a good night’s sleep and gigantic breakfast. The day started in the hotel lobby where we were greeted by our host Dr Brian Jackson, who took us for an introductory tour of the city and NCSU campus starting with the department of horticulture.

The Department of Horticulture

The department is large and diverse covering many aspects of horticultural science including urban horticulture, growing media for greenhouse and nursery production and ornamental plant production. To give you an idea of scale, the department has an average budget of about $4 million dollars, employing around 50 staff and teaching 282 undergraduate and 40 graduate students. What’s more impressive is the land – the college owns about 2,000 acres which contains all kind of research platforms from arable fields to an experimental pig farm. The first thing we did was drive around the campus and associated university land. It took us a good hour to circle round the relevant areas, including a quick tour of the epic university library*

The NC State farmers Market and a ‘Southern Boil’

Next it was on to the local farmers market to have a look at what some of the small scale growers were producing in and around Rayleigh. This market is one of four such enterprises around NC and is owned and operated by the state department of agriculture. These markets are designed to encourage small and medium scale growers by offering them a subsided space in a prime location to sell their produce. The market has about 30,000 sq. ft. of space for the sale of ornamental and edible container plants to the general public, as well as a separate wholesale terminal for supply to local businesses.

The market was a bustling hub, and the growers seemed to be doing a brisk trade. What struck me was the sheer diversity of plants on offer, as well as the generally excellent quality (fig. 1). The other really attractive aspect of this place, was that it was possible to talk to the growers themselves about the plants. It was clearly a forum to exchange horticultural information as well as buy and sell plants. I can’t think of anywhere equivalent in the UK, perhaps one of the larger flower markets in London such as Covent Garden? From a UK perspective, I think there is a gap in the ornamental plant market for something similar. With the rise in popularity of small local farmers markets, why not a subsidised ornamental plant cooperative in or around London?

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Suitably inspired, it was off to the home of Dr Bill Fonteno for the evening, where we experienced our first ‘Southern boil’. This sounded like some terrible bodily affliction but turned out to be a rather delicious local dish cooked with shrimps (prawns), sausage and potato. We were joined by another visiting researcher, Dr Jean-Charles Michel, an expert in physical properties of growing media and based at the University of d’Angers in France (more on him later). This was a great opportunity to exchange ideas in a relaxed atmosphere.

*I feel the recently build James B. Hunt University library needs a special mention here, for me it represents the kind of innovation and investment so sorely missing from UK higher education. It is an immense, beautiful building covering 221,000 sq. ft. and dominating the skyline at over 88ft. tall (fig. 2). It also represents a truly staggering investment; it cost $115.2 million, of which $93.75 million came directly from the state. Walking into this building is like walking onto the set of some futuristic science fiction film. There are no books, instead there is a massive, environmentally controlled vault (helpfully displayed to the public, through a glass wall). In this vault are rows and rows of stacked containers, this vast system can hold up to 2 million volumes in 1/9th the space of conventional library shelves. If you are old fashioned enough to need an actual hard copy of a book, you must go to a computer screen and request the book you require. After a few seconds the computer will locate the book and send (and this is where it gets really mind-blowing) a 16ft tall robot to retrieve it from the giant stacks. It’s all over in a minute or so and there is no danger of any time wasted idling between bookshelves. This lack of shelving also means the actual library is just one airy, bright room

N. Bragg /Bulrush

N. Bragg/Bulrush

Fig. 1 Images showing the diversity and quality of plants being sold at the he NC state run famers market

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after another full of comfy seats, computer terminals and communal white-boards. In fact there are over 100 rooms all cleverly designed to encourage and inspire learning and the atmosphere purrs with quiet conversation. A truly inspirational place representing in my opinion a truly awesome but admirable investment of government money.

Fig. 2 The elegantly curved, recently built NCSU library

20th Tour of the Horticultural Sciences Department and a departmental seminar with staff and students.

A new day and another enormous breakfast with our hosts, where I learned that in the US biscuits are actually a type of savoury scone……confusing. With a very full tummy and a vow never to eat so much again, it was onwards into the days packed itinerary.

JC Raulston Arboretum

A perfect way to start the day as the sun was out and the dew was rising. The JC Raulston Arboretum was established in 1975 by the university to serve as a living laboratory for students and faculty staff, a resource for green industry professionals and an educational space for the general public (fig. 3).

I could probably spend many pages describing the fabulous diversity of plantings in this garden but I’ll mention a couple of the things that caught my eye. The ‘Xeric’ or dry garden, was a mixed of drought tolerant plants from all over the world including a good mix of local species found in the Carolinas and Virginia. I also enjoyed the incredible diversity of conifers, the garden contains more than 400 taxa in all shapes and sizes. This collection has a very practical use, it’s essentially an experiment to try and diversify the selection of conifers available for planting in the Southern US gardens. It was one of the first collections in the US to show the adaptation of a wide range of species to the humid climate and heavy clay soils of the South Eastern US. It was also pleasing to see that the gardens are open to the public for free, and that a range of out-reach events regularly take place to encourage local community involvement.

N. Bragg /Bulrush

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Fig. 3 Images from the JC Raulston Arboretum, a garden run by NCSU; a) Map of the garden, b) visitor centre with green wall and c) a Geophyte border

Tour of the Horticulture Field Laboratory and substrates processing and research centre (SPARC)

Adjacent to the arboretum is the horticulture field laboratory, where many aspects of ornamental plant production are investigated in commercially realistic systems. There were many things to see here, and we didn’t have enough time to cover them all. A highlight was the work being carried out on water-use efficiency in container grown hardy nursery stock. The researchers had developed a simple but effective way of measuring the amount of water running-off typical ornamental nursery beds. Container plants were grown on raised beds of mypex topped sand. These beds were on a slight gradient so that all water running off the pots ran down through the bed and collected in a pipe at the end (fig. 4). This could then be siphoned off and measured to determine how much run-off was being generated during an irrigation event. One of the biggest future challenges for growers in both the UK and the US is how best to improve water-use efficiency in container grown plants. Ideally, growers whether professional or amateur want to maximise the amount of water that they get into the pots and reduce the amount running out (which is often laden with nutrients and therefore damaging to the environment). A simple system like this provides a practical way of measuring the effectiveness of different irrigation methods or regimes. It’s a system we could use within the remit of the fellowship - one of our key research objectives is to increase the sustainability of water use in horticulture.

N. Bragg /Bulrush

P. Alexander/RHS

P. Alexander/RHS

a) b)

c)

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Fig. 4 Experimental water capture beds at the NCSU Horticultural field laboratory

Our next stop was at the substrates* processing and research centre (SPARC). Before I describe our visit to this area, I should probably tell you a little more about our host Dr Brian Jackson. Before my trip to the states I was very familiar with his work, he is a prolific author on the topic of container growing media and his published articles have been very useful to me. As I outlined in my introduction, pine bark is becoming increasingly expensive in the US and researchers like Dr Jackson are searching for cost effective alternatives with which to make growing media. What they have no shortage of in NC is land and much of this is forested. This has given researchers an idea for a new approach to sourcing raw materials for growing media; instead of relying on by-products of another industry, why not grow trees specifically for the purpose?

*The US researchers refer to container growing media as ‘root substrates’

Pine Tree Substrate (PTS)

From this idea came pine tree substrate (PTS)2,3 a material made from whole pine trees grown solely for use in growing media. Fast growing pine species such as loblolly are grown in short-rotation, the whole trees are then chipped in a large machine called a hammer mill and the wood chips are then screened according to their size. Smaller particle size ranges create a growing medium that will hold water well, larger particles will help to keep a growing medium ‘open’ or well-drained and aerated. By using the correct combination of screens, a PTS can be created that is well suited to any number of different plants species and commercial production systems (fig. 5). Dr Jackson and his team at NCSU, have spent several years perfecting the optimal range of particle sizes for different sectors of the US Horticultural Industry. The material has also been trialled successfully on several herbaceous and woody plant nurseries. I’ve spent the last year of the fellowship working on constructing my own peat-free and peat-reduced growing media for woody nursery stock. I’ve learned a lot from the approaches taken by Dr Jackson and his team and it’s great to be able to question him about this approach to growing media design.

Water collection pipe

Mypex covered raised beds

N. Bragg /Bulrush

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Fig. 5 Finished pine tree substrate (PTS), manufactured at the substrates processing and research centre (SPARC)

So back to the SPARC which comprises of an open fronted warehouse dedicated to the production of PTS. Inside is an impressive range of machinery including a hammer mill (fig.6a & 6b) and screening areas where giant sieves (fig.6c) of varying sizes are stacked up ready for the next batch of wood chip. This facility means researchers can control every stage of the production of PTS, from chipping the freshly harvested logs to bagging up the final product. Not only does this aid in the consistency of their experimental work, but also demonstrates a drive towards the commercialization of PTS. As Dr Jackson points out, this set-up might sit comfortably in a large nursery enterprise or might be purchased by a consortium of smaller growers. This would allow them to manufacture their own growing media more cheaply than they are currently buying it in. What’s more important is that PTS is truly ‘sustainable’, it’s produced locally from trees which can be re-planted after harvest. While there is still more work to be done in terms of making PTS a fully commercially viable product, it’s impressive to see how horticultural research is being practically applied to solve a real world problems.

P. Alexander/RHS

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Fig. 6 The kit used to produce pine tree substrate (PTS) at the substrates research and processing centre; a) the hammer mill, b) inside the body of the mill are metal hammers which pulverise the pine tree logs into wood chips and c) The screening area where wood chips are screened to different particle size ranges.

Tour of the Horticultural Growing media Laboratory and glasshouses

It’s a 20 minute drive across the vast campus area back to the department of horticulture, where we are given an in depth tour of the laboratory space and glasshouses. Much of the kit described was probably of little interest to anyone other than a growing medium researcher so I’ve picked out some choice highlights.

The ‘Horhizotron’

Since I started working with growing media two and a half years ago, I’ve been intrigued by the way in which plant roots respond to different materials. There are clear changes in the rate and pattern of root growth and we know this has important implications for plants when they are transferred from pots into people’s garden soil. I spent a few weeks in my first year picking

P. Alexander/RHS

a) b)

c)

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out roots and weighing them to see if I could actually detect a difference in root growth between different growing medium types. This method was laborious and could tell us nothing about the differences in root architecture that were clearly developing. Researchers at NCSU have noticed the same differences and have come up with a very neat solution for measuring them. It’s called a ‘horhizotron1’ or ‘rhizometer’1; it’s an impressive sounding name for what is actually a simple piece of kit. It’s a modified container with three chambers, each containing a Perspex viewing window (see fig.7). A plant sits in the middle of the container and the roots grow out into the three chambers. The sides of each chamber can be removed when required and the pattern of root growth observed. It’s a powerful tool because each chamber can be filled with a different type of growing medium and the root responses of one individual plant compared directly. Dr Jackson and his team are currently incorporating image analysis software, so that photographs can be used to quantitatively measure differences in root system area and structure. As we have long suspected from our own observations at Wisley, the team at NCSU have been able to show that wood based substrates do seem to increase root proliferation in containerized plants. It’s truly fascinating stuff and definitely gave me food for thought, could we use a simplified approach to look at root structure in the fellowship research?

Fig. 7 The ‘Horhizotron’ a specially modified container which allows root growth to be observed and measured; a) an empty horhizotron showing the three chambers, b) the planted unit and c) a close-up of the root architecture in a peat and perlite growing medium.

b)

c)

a)

N. Bragg /Bulrush N. Bragg /Bulrush

P. Alexander/RHS

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The NCSU Growing media processing Laboratory

The next area of note is the large growing media processing laboratory where the team at NCSU have helped developed a national standard for container growing media quality4. This area is very much the creation of Dr Bill Fonteno, head of the growing media research group at NCSU. He is one of the foremost researchers in the field of container growing media and has developed some of the standard methods used world-wide for measuring the physical properties of growing media.

When I say ‘physical properties’, I mean measuring the way in which the particles making up different growing media interact to hold air and water. The root systems of plants in containers have a fraction of the volume they would have when planted out in the soil. The key to creating the ideal container environment is finding a material or combination of materials that holds both water and air in the correct balance to support healthy root growth. This is actually quite a tall order because when a material holds water really well, it often does so at the expense of air i.e. the holes or pores in the material tend to be filled with water rather than air and roots can suffocate. Equally if the pores are too large and hold much more air than water, plants risk drought stress between irrigation events. A good growing medium is essentially a material or mixture of materials which have the right combination of pore sizes to keep roots breathing and hydrated.

Alas, growing media manufacturers don’t always get this right and as many a UK gardener can attest, bagged growing media available off the shelf can vary widely in its ability to support healthy plant growth. The first experiment that I ran back in 2012 compared the performance of four proprietary multi-purpose growing media from local garden centres. These four products clearly contained different materials and this had a profound impact on the resulting quality of the Pelargoniums produced. When growing media go wrong, the results are horrible – all round plant failures no matter how carefully the plants are tended. The crux of the problem is that there is no universal standard in the UK for growing media quality and gardeners quite often have no way of knowing a) what’s in their chosen bag of compost and b) how well it will perform.

They’ve had the same problem in the US but NCSU researchers have worked with the industry to developed something of a solution – the mulch and soil council certification program.

Mulch and Soil Certification program

This program was established in 2000 by the Mulch and soil council, an association for the manufacturers of container growing media, soil amendments and mulches (akin to the UK growing media association). The aim was to improve quality and fairness of pricing, through the introduction of a growing medium standard. The mulch and soil council worked with Dr Fonteno and his group to create a list of essential criteria for this standard, including bag labelling specifications, volume testing (to check that the volume of product stated on the bag is actually what the consumer gets) and plant performance assessments (Fig 8a). In order to achieve certification under the program, growing media manufacturers must submit samples of their products to the NCSU horticultural growing media laboratory for independent testing (Fig 8b). Once the samples have passed, the mulch and soil certification logo can be displayed on product bags and packaging. Manufacturers are then annually audited to ensure that quality is maintained year on year.

This quality assurance logo is instantly recognisable to consumers and the program has been immensely successful (in 2014, 1.5 million bags were produced bearing the logo). Although a

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voluntary scheme, consumer preference for products bearing the logo has steadily grown which has incentivised more manufactures to participate…… it’s now the biggest program of its kind in the US. NCSC receives around 1,000 bags of growing media per year for testing and it’s an excellent source of revenue for the horticulture department. It’s empowered gardeners by giving them an informed choice about the products they buy and it has forced some of the really bad quality products out of the marketplace. What really impressed me about this scheme, was the degree of cooperation between researchers and manufacturers. It’s an ideal model for the UK, where the drive to reduce peat content of growing media has meant that gardeners are faced with a huge number of growing media options, and no real way of knowing what they are buying or how it will perform.

Fig 8. Images from the NCSU growing media processing laboratory; a) plant growth testing of bagged growing media for the soil & mulch certification process and b) stacks of bagged growing media awaiting testing

Growing media group seminar

After the tour of the laboratory it was onto a lunch-time seminar where our hosts had arranged a series of talks from fellow scientists and students. We learned about a Master’s project investigating the hydration and wettability of different container growing media and PhD projects investigating the use of biochar and other novel materials in growing media. All of these topics were of relevance to the work we are doing here at Wisley and it was fascinating to see the approaches taken by other researchers to problems I had tackled myself. Nitrogen draw-down* in growing media is something I’ve done a lot of work on because it’s an important issue in many peat-reduced and peat-free growing media. I’ve attempted to measure it and found the established methods extremely time-consuming and of limited practical application. Much to my excitement there was a PhD student whose project was dedicated to developing a practical way of assessing nitrogen drawn-down in a range of different growing media materials. With 4 or 5 years to work on the problem within such an excellent research group, I have no doubt that much progress will be made. I found myself able to offer some advice to the student and I hope to maintain contact on my return to the UK.

P. Alexander/RHS

a) b)

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Paul, myself and Neil all gave presentations to provide the group with background on what was happening in the world of UK growing media. Paul’s talk was titled ‘The Royal Horticultural Society and Horticultural Research for Gardeners’ and gave a broad overview of the work of the RHS and science team. I then followed with my talk ‘Improving the sustainability of growing media in professional and amateur horticulture’. This was an introduction to the Fellowship project and gave some of the highlights of my work to date (see attached appendix). Neil finished with an outline of the AHDB – horticulture ‘Horticulture beyond the garden – The work of the AHDB – horticulture’. The presentations were well received and generated a lot of discussion. I think there was realisation on both sides of just how much similarity there is in the challenges faced by both UK and US researchers.

Departmental Seminar

After several hours of discussion we relocated to a large lecture theatre to participate in a departmental seminar by Dr Jean-Charles Michel on the ‘Wettability of horticultural substrates’. Dr Michel is an assistant professor in soil and growing media science at Agrocampus Ouest in Angers, France. He was awarded a Fulbright research fellowship and has been working at NCSU for the last 3 years. He is coming to the end of this sabbatical leave and we were lucky enough to be present as he summarised his accomplishments while at NCSU. Dr Michel is an expert in the physics of horticultural substrates and is particularly interested in the way different materials absorb and retain water (‘wettability’). His forte is using mathematical models to describe the way in which water moves through different growing media. While the actual mathematics behind these models is bewildering to all but a select group of boffins, the practical outputs are extremely useful. These models can help predict how well specific growing media will work within different plant production systems. The information can also be used to optimise irrigation regimes and therefore increase water-use efficiency on professional nurseries. It was clear that Dr Michel has gained a great deal from his time working at NCSU. The excellent facilities present in the laboratory and wealth of existing knowledge have allowed him to expand his research into new areas. I hadn’t realised that such opportunities existed for horticultural scientists and it’s certainly got me thinking about where my research might take me in the future.

After a brief break at our hotel to rest our brains it was back out for dinner with several members of the research group to continue discussions in a more informal setting.

* Nitrogen draw-down5 describes the process where microorganisms naturally present in organic material take-up and immobilise inorganic nitrogen leading to plant deficiency. This process can be problematic in wood-based growing media particularly if the raw components haven’t been aged or composted appropriately.

21st A day of touring near-by growing media manufacturers and nurseries

A perfect day for touring, the sun was out and the temperature was climbing. The first-thing to note is that ‘near-by’ in the US isn’t the same as ‘near-by’ in the UK. The first visit of the day was to a pine bark growing media processor and supplier and it took us almost two hours of driving to reach our destination. Our host for the Day was Dr Fonteno and we were also accompanied by Dr Michel (who being so consumed with his research had yet to visit a US growing media manufacturer).

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Pacific organics

This relatively small operation is situated north of Rayleigh near the North Carolina/Virginia border. When I say small, it’s quite large by UK standards covering an area of about 28 acres. This company specialises in supplying premium growing media to professional growers and landscapers and the focus is very much on quality. The production process is summarised in fig. 9. Pine bark is shipped into the site from lumber yards, this is then aged in large piles (windrows). This aging process sees the bark starting to compost and heat up. This drives off any phytotoxic compounds and increases the wettability of the materials. The windrows are turned periodically to ensure the material is homogenised and evenly aged. The length of the ageing process also affects the physical properties of the resulting pine bark. Material that has been aged longer tends to produce finer particles which are better at retaining water. Once the aging process is complete the windrows are graded into piles containing different particle sizes. Different grades can be combined to produce potting mixes for a range of different applications. For instance, larger particles sizes are included in the ‘Aeration + potting mix’ for plants which require high levels of air in the root zone. In contrast, the ‘Hydrating potting’ mix contains a higher proportion of finer particles to increase moisture retention. This growing media manufacturer takes a refreshingly scientific approach to production, routinely measuring the pH and electrical conductivity* of their pine bark to ensure the aging process has produced adequately stable material. They also test the moisture and air retention of their potting mixes using methods developed with the help of the NCSU growing media group. Walking around the site, it’s clear that this is a very well organised set-up and the staff are extremely knowledgeable (fig. 10). They have obviously benefited a great deal from working with Dr Fonteno, and their understanding of growing media science has allowed them to produce a consistent high quality product. This means they have a solid base of loyal customers who come back to them season after season.

*Electrical conductivity is a commonly used measure in horticultural science, it is an indirect measure of the concentration of ions in a solution. In this context the manufacturer uses it to assess the amount of soluble salts present in the ageing pine bark. If the ageing time has been insufficient these may be present in very high concentrations which are then toxic to plants.

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Fig. 9 Outline of the pine bark growing media production process at Pacific organics, from the reception of raw materials (1) to the production of the finished growing media (2). All images by Paul Alexander/RHS

1. Pine bark arrives from lumber yards

2. It’s aged in windrows

3. Then screened into different particle size ranges

4. Then mixed according to physical properties required

5. The finished product

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Fig. 10 Each stage of the pine bark growing media production process was explained; a) The site owner explains the grading process and b) the foreman answers questions by Dr Michel.

Old Castle Lawn & garden

We are back on the road for another 40 minutes or so before we arrive at our next visit. A large scale producer of mulch* for the retail and landscape markets. This site manufactures millions of bags of mulch every year for sale all over the South Eastern US. It’s an operation on a scale I’ve not seen before - what seems like mile after mile of pallets piled high with bags (fig. 11a). Given the scale of the operation it’s a much more formal visit than the previous one. We are signed into the sight on arrival and given high visibility vests – the site is much too big for a tour on foot so we all pile into the foreman’s truck. We start off at the far end of the site which looks a bit like a lumber yard (fig. 11b). Given the amount of product manufactured here they simply buy in whole trees and chip them on site. There are huge machines everywhere churning out an incredible amount of noise and dust.

Like growing media, mulches vary widely and there are many different types which offer a range of benefits depending on factors like particle size range and tree species. Mulches made from cypress, cedar and eucalyptus are most widely favoured because they are very resistant to decomposition and only need to be re-applied once per year. We also discovered that coloured mulches are quite popular with landscapers. The problem with un-dyed or ‘natural’ wood mulches is that they often discolour in the sun fading from a nice brown to a drab grey. To over-come this, mulch manufacturers use non-toxic dyes to colour their chipped wood products (fig. 11c). A range of colours can be manufactured but black, brown and red seem to be the most popular (fig. 11d). Our tour included a visit to the mulch dying machines, massive pieces of machinery where mulch is loaded into giant hoppers and sprayed with a mixture of liquid colorant and water to produce a product of the desired colour (fig. 11c).

a) b)

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Fig. 11 Images from the large scale mulch producer Old Castle lawn & garden; a) Stacked pallets of bagged mulch for the retail market, b) The raw material for the mulches; whole logs of different tree species, c) the machinery used to dye the mulches and d) some of the finished dyed mulch products including (clockwise from the left) brown, red, gold and black.

*Mulches and Mulching

Mulching is a much more popular in North Carolina and Arkansas (and I suspect elsewhere in the US) than in the UK. As we toured around Rayleigh on the first day of our visit we all noted the amount of mulching going on (as you do). Every flower bed, every planted slope – even the base of every tree was mulched (see image of bed on the left). Its common practice for both professional landscapers and gardeners, because a covering of mulch helps to retain soil moisture, maintain a constant temperature at the soil surface and supress weeds. I’m a big fan of mulching, I think the worse way to treat soil is to leave it bare and open to the elements where it can become eroded by wind and water. In the states mulching has also become a bit of an art form with coloured mulches used to complement planting schemes. It’s quite a nice idea, I wonder if we might try something similar at Wisley to try and encourage more UK gardeners to get mulching.

a) b)

c) d)

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Summary and conclusions of visit to NCSU

A fantastic three days, we were all surprised at just how much our hosts had managed to squeeze into such a short space of time. Seeing such a large and vibrant centre for horticultural science was truly inspirational. Belonging to a small research group here at Wisley with so little growing media research being carried out elsewhere in the UK it is easy to feel isolated. This visit made me realise that I’m actually part of a community of researchers and that I can use this network to share ideas and knowledge.

It was interesting to see just how well Dr Fontano and Dr Jackson engage with growing media manufacturers. It’s clear that their research findings are being communicated in a practical way to the industry through their extension and out-reach work. I think this is an important lesson for the fellowship project, we need to ensure we find ways to communicate our findings clearly to RHS members and professional growers alike – this is just as important as peer-reviewed scientific publication.

It was great to have the opportunity to talk about my own research to a group of experts in my field. Not only do I have countless new ideas for my work but also a group of people who I contact for specialist information and collaborative opportunities.

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PART II HORTICULTURAL SCIENCE IN ARKANSAS

An introduction to Arkansas and The University of Arkansas (UA)

Map 2 The location of Arkansas in relation to the rest of the USA. The city of Fayetteville is marked with a star

Arkansas is located in the Southern half of the US, and our destination was Fayetteville in the North-western corner of the State (map 2). The city is on the edge of the Boston mountain range and in the heart of the Ozark Plateau, a geologically unique highland region which dominates the central US. It’s a beautiful, forested landscape interspersed with dairy farms and poultry houses (the poultry industry is one of the region’s most important) and quite different from the flatter terrain in and around Rayleigh. Fayetteville is a rapidly expanding urban hub and the home of six fortune 500 companies including the world’s largest company, Walmart.

The University of Arkansas (UA) was founded in 1871 as a land-grant institution, it’s a little smaller than NCSU with a student population of around 26,000 and about 4,000 staff. The main university campus is situated towards the centre of the city and occupies about 72 acres. The University is the area’s largest employer and comprises of 10 colleges with the department of horticulture belonging to the Dale Bumpers College of agricultural, food and life sciences.

22nd Brief tour of Fayetteville

Unfortunately much of the day is spent travelling, there are no direct flights to Fayetteville from Rayleigh so we have to take two flights, changing at Atlanta in Georgia. It’s a good chance to

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relax a bit and reflect on our experiences so far. At Fayetteville airport I’m slightly alarmed that the ladies toilet also doubles up as a tornado shelter but with a clear blue sky and not a cloud in sight, I decide it’s likely to be a fairly calm evening.

We are met at arrivals by our host for the next few days Dr Michael Evans, who leads us out to his giant truck. He is kind enough to give us a whistle stop tour of Fayetteville on route to our hotel. It’s clear that this is city is on the rise with new buildings going up everywhere, and roads being rapidly expanded to cope with the swelling population. In the last few years Fayetteville has become a magnet for businesses, particularly those pertaining to the food processing industry and the outskirts of the city are dominated by shiny new industrial estates. Before dinner we are treated to a tour of the down-town area which is beautifully landscaped. We come across plantings of ornamental and edible plants in the central square (fig. 12) and the streets are tree-lined with flower laden raised beds tastefully interspersed. The city employs three full time horticulturalists to design and maintain these displays and we are all impressed with the quality of horticulture on display. Over dinner, which consists of the best burger I’ve ever tasted, we get to learn more about horticultural science at the UA.

Dr Evans is a professor specialising in greenhouse and nursery growing media. Over the last decade his group at UA have developed an internationally recognised research program. This has helped to introduce a range of new growing media materials into the nursery and greenhouse industry in the US including coir, part-boiled rice hulls6,7, poultry feather8,9 and growstones (a recycled material made from glass and used to increase aeration in place of perlite or pine bark). The group have developed a number of analytical techniques used by the industry for evaluating and characterizing container growing media. Dr Evans is also responsible for developing and teaching courses on controlled environments, greenhouse crop production and floriculture. Like Dr Jackson and Dr Fonteno a large part of his time is dedicated to teaching, the US universities really do seem to make this the primary focus of their academic staff.

Fig. 12 Amenity planting in the downtown region of Fayetteville. The city employs 3 full-time horticulturalists to maintain planted areas across the city.

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23rd Tour of the UA campus, department of Horticulture, departmental research seminar and meetings with horticulture staff and students

The day starts early with a 20 minute drive to the University campus in rush-hour traffic of the sort you might find on the M25 near Wisley. We start with a brief tour of the leafy central campus. The university has invested about $ 500 million in the last couple of years and the facilities and infrastructure are impressive.

The department of horticulture

The department of horticulture is our next stop which is housed in the large plant sciences building and surrounded by a beautifully landscaped garden (fig. 13). This is a training garden which gives students the opportunity to try out their practical skills. The department offers a range of horticultural qualifications including a BSc and MSc in Horticulture. It is divided into 5 groups: fruit, vegetable, sustainability, ornamental and landscape and turfgrass. In addition to offices for staff, graduates and students the department has 5 research laboratories and shares space in a recently built facility called the ‘Rosen alternative pest control building’, which includes state of the art greenhouse space, growth chambers and teaching laboratories. The department also runs an experimental research centre 1.5 miles from the main campus (more about this later).

Fig. 13. One of the many sculptures on the beautifully landscaped campus, this one features the university mascot - the razorback hog (with Neil Bragg).

We spend some time in a laboratory where Dr Evans has recently installed two small growth chambers. He is running an experiment investigating the potential of different growing media to control red spider mite. The growth chambers are state of the art and brand new, the department seems very well-funded. We are curious as to where the money for research comes from – is it state funded? Is there some equivalent to a research council? Dr Evans explains that horticultural research at the university used to be mainly government funded but the last decade has seen this source of income dwindle. While there is still some state funded research going on much of the money now comes from industry. Dr Evans is currently running some 10-12 projects funded by individual companies who are interested in all manner of growing media related topics from pest suppression to new substrates for hydroponically

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grown lettuce. We do wonder whether this means researchers feel pressured to endorse certain products or systems that they are testing, but Dr Evans assures us that the companies just buy the data. It’s interesting to hear that researchers in the US have faced the same cuts in government funding as we have in the UK. They have clearly been quite good at finding alternative sources of money and I wonder whether UK researchers can learn something from their pragmatic approach.

We then move on to a tour of some of the glass house space within the department. Much of Dr Evan’s work is focused on growing media for hydroponically grown fruit and salads. The production system he is using here is known as nutrient film technique (NFT). This system uses a thin flow (2-3mm deep) of nutrient solution inside growing channels. Plants are placed in small plugs of soilless growing media (oasis in this case) inside these channels where they rapidly develop a dense root mat. Nutrients and water are then obtained from the constant re-circulating flow of nutrient solution. The upper part of the plant grows out of the channel through a hole in plastic where it can be easily harvested. Growing plants in this way allows for conditions to be carefully controlled (fig. 14).

Fig. 14 Lettuce grown hydroponically using Nutrient film technique (NFT). The blue arrows represent the flow of nutrient solution around the system of channels. There is a close up image of a channel in cross section to display the root matt and thin film of nutrient solution.

Reservoir of nutrient solution

Plastic Channels

Root matt inside NFT channels

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We looked at several pieces of work, the first was an experiment to investigate how the concentration of the nutrient solution influences the growth rate of lettuce seedlings (fig. 15). The second piece of work was to determine how pathogenic bacteria can survive within the nutrient solution as it travels through the system of channels. There has been increasing concern in the salad production industry about the presence of dangerous bacteria like E-coli and Listeria. Dr Evans and his team have deliberately introduced some species of bacteria to these systems to better understand a) how they survive and b) the best ways to remove them.

Fig. 15 Dr Evans and Neil Bragg discuss an experiment investigating how different concentrations of nutrients influence hydroponically grown lettuce seedlings.

Departmental seminar

After tours of a few more laboratories, it was time for the departmental seminar and we were the guest speakers. The seminar was advertised around the department (we saw the flyers to prove it) and the classroom soon filled up with staff and students keen to find out about our work. After a few glitches with the technology (this is really state of the art stuff, no-one could even find the computer at first which was built into the massive screen), we are off giving the same talks as a few days ago at NCSU. It’s a bit more formal this time with a lot more people. The talks were well received and generated a lot of discussion. I’m not sure there is anything analogous to the RHS in the US and the group seem generally impressed with the scope of research the charity are doing. There were also many questions about peat replacement - this isn’t an issue in the US and the students in particular, were keen to find out more. It was a really good opportunity to talk to other researchers about my own work and I know its good practice for me. Public speaking is par for the course if you want to be a scientist - it has got easier over the years but I still get nervous.

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Horticultural Education and Internships

After a quick lunch in the vast student union food court (the hardest thing was knowing what to choose), we had a meeting with Dr Leslie Edgar, director of International programs. Undergraduate students enrolled for a degree in Horticulture at UA are required to undertake at least one internship to help equip them with the practical skills they will need to make successful careers in the US horticultural industry. One of the areas which Dr Edgar is particularly interested in promoting, is horticultural and agricultural science communication. A recently successful project involved sending a group of undergraduate students off to Ghent in Belgium where they were placed with horticultural research companies. They were asked to help re-brand the work of these companies so that members of the general public could better understand the value of what they were doing. The idea was to use these young people to make horticultural science more accessible and equip the students with skills that would make them more employable. It’s interesting to hear that the students have to minor in subjects like ‘agricultural communications’ as well as taking courses in more traditional horticultural subjects. This certainly makes sense to me and I wonder whether we could do more in the UK to make our PhD students more employable? We talk about the possibility of providing internship placements for US students at Wisley within the science team or at the AHDB-horticulture. It’s an interesting prospect and one I think all parties could benefit from.

On-line learning – greenhouse management

Continuing on in the theme of horticultural science education we are back with Dr Evans next, to talk about the online course he has designed in greenhouse management. The horticultural department of the UA is a member of ‘The Alliance for cooperative course exchange in plant sciences (ACCEPtS)’. This is a consortium of universities which has worked together to create an online resource of undergraduate and graduate courses in horticultural science. Each institution involved has its own specialisms and by working together the universities can pool their knowledge and increase the number of courses they offer. Additionally, off-campus students can achieve higher level horticultural qualifications through distance learning.

This online resource has been built up over the last 10 years and contains 11 degree level horticultural courses from ‘Sustainable nursery production’ taught by Oklahoma state university to ‘Horticultural crop physiology’ taught by Louisiana state university. Dr Evans gives us a quick tour of his course on greenhouse management. This is 15-16 week course containing multiple formats for learning. There are online text-books, videoed lectures, videos of practical techniques (like measuring the pH of a growing medium) and online blackboards where students can leave questions for the lecturers. There are weekly assignments including essays and tests, with students collecting points as they progress through their chosen course. The resource is also available to industry professionals and is a particularly useful format for those already in work but wanting to increase their skills and qualifications. The cost is relatively low ($600-$700 for a 16 week course) so affordable for many smaller businesses wishing to improve their skill set. The online format means that students can enrol from companies and universities all over the world.

It’s an innovative approach to learning in the online age and I wonder if the concept would work in the UK? We have small, relatively specialised institutions doing horticultural themed research and offering horticultural qualifications. No single institution is particularly well funded or resourced - could a consortium of institutions, including the RHS offer a solution? By pooling the expertise of a group of researchers might it be possible to create a similar online resource? At the very least it’s useful to know this resource is out there, it could certainly offer UK

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students and industry professionals a chance to acquire some of the expertise the US has to offer.

It’s been an extremely interesting day, we round it of by having dinner with a few of the senior academics from the department. It’s a chance to try a local speciality – fried cat-fish which is actually surprising similar to battered cod…but disappointingly they haven’t heard of mushy peas!

24th Tour of the UA experimental research and extension centre followed by local nursery visits

It’s an early start as we attempt to reach the experimental research and extension centre before the rush hour traffic hits the road. It’s a large site about 1.5 miles from the main campus area and consists of experimental turf plots, orchards, vineyards and high tunnels for bush fruit (fig. 16a), strawberry beds (fig. 16b) ornamental plant collections and additional glasshouse space. Every sector of the horticultural industry seems to be represented and we are here to meet with several of the researchers who work at the site.

Fig. 16 The UA experimental research and extension centre; a) high tunnels for bush fruits and b) some strawberry beds with rain shelters

Turfgrass Projects

Our first meeting is with Dr Doug Karcher, an associate professor specialising in turfgrass science. The aim of his work is to improve the functional and aesthetic quality of turfgrass by investigating cultural practices and improving soil management. He walks us around the 10 acres of experimental plots (fig. 17a) and explains that the sport’s turf and lawn care industries are big business in the US. His work has a broad remit from trialling different water management strategies on golf greens to experimenting with new grass hybrids. At the moment, his team are carrying out experiments to test the resistance of several grass species to Rhizoctonia, a fungal disease. This disease leads to large patches of grass die-back which are particularly problematic for the golf industry (fig. 17b). He also remarks on some work being carried out by imposing drought conditions on turfgrass plots composed of different

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grass species. Unfortunately, the research centre sometimes sees some pretty dramatic weather and the project has been stalled because the rain shelters have blown away.

Fig. 17 Experimental turfgrass plots; a) an overview of the area and b) a close up of the experimental plots, clearly some treatments are much more successful than others.

Fruit Projects

Next we meet with Jason MacAfee, a senior technician working in the fruit science division. The UA has an extensive fruit breeding and genetics program and has commercialised around 70 cultivars of strawberry, peach, grape, blueberry and blackberry. We learn that much of the fruit science research is carried out at another research station at Clarksville, a town about 85 miles south east of Fayetteville. This facility consists of 230 acres of field plots, greenhouses, a cold storage facility and laboratory but we don’t have time to visit unfortunately.

Jason talks us through a project in which they are using high-tunnels (poly-tunnels) to extend the blackberry, blueberry and strawberry season in Arkansas from the early spring right up to the end of the autumn (fig. 18). They have also been experimenting with tunnel heights and ventilation systems to induce the best conditions for optimal fruiting. There is much more to see including projects on organic apple production and the pruning and management of grape vines.

Fig 18. The experimental poly tunnels or high tunnels which are being used to manipulate the fruiting season for a range of bush and cane fruits including blackberries, raspberries and blueberries.

a) b)

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Greenhouse edible crops

Dr Evans and his team have green house space at the research station and next he takes us on a tour of this. The first stop is a house full of lettuce which is being grown in a NFT system. This is a project to trial blocks of growing media made out of different materials including the standard oasis cubes, coir cubes, peat cubes and rockwool cubes. He lifts out some of the plants from their channels so that we can see how the different rooting media have influenced root development (fig. 19). Oasis cubes are used widely at the moment by both professional and amateur hydroponic growers. While effective, they are not recyclable or reusable so present a bit of a disposal issue. Thus, researchers are looking for more environmentally friendly alternatives - it’s a familiar story. It makes me realise that the skills I’m learning working with ornamental, container crops are actually very transferable to other areas of the industry.

Fig. 19 Blocks of growing media used in hydroponic production of lettuce; a) the block fits into the hole at the top of the NFT channel, b) the resulting root growth through the block, the density of root growth varied according to the type of growing media block used in the system.

The next greenhouse contains a different hydroponic system for growing strawberries –Dutch buckets. These are plastic buckets filled with a simple porous soilless growing medium, perlite in this case. The base of the bucket contains a reservoir for nutrient solution which is drawn by capillary action up through the perlite to supply the plant roots. The reservoir is topped up periodically from a central reservoir of nutrient solution (fig. 20).

a) b)

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Fig. 20 Strawberry production in a Dutch bucket hydroponic system; a) Dr Evans (centre) talks Paul Alexander (left) and Neil Bragg through the technical details and b) the system in close-up with the Dutch buckets attached to a central nutrient solution reservoir below.

Dr Evans and his team like this system because it offers a great deal of flexibility to the grower as individual buckets can be taken on and off the system as required. The team have also been working on suspended versions, akin to hanging baskets which might be useful for maximising space in greenhouses and gardens (fig. 21). Dr Evans has been growing different cultivars of strawberries in both of these systems to see which ones are most well suited.

Fig. 21 A modified version of the Dutch bucket system with strawberry baskets suspended from the roof of the glasshouse. This is an experimental system for maximising space usage in professional set-ups but may also work for amateur gardens with restricted space.

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There’s a lot more to see including a masters project investigating how the depth of soilless growing media (expanded clay) in an ebb and flood* hydroponic system, influences lettuce growth (fig. 22). It’s hoped that lettuce quality can be maintained in a shallower bed of media, reducing production costs for the grower. This is particularly important, as these systems tend to be used by small-scale professional growers or amateurs.

*Ebb and flood system – also known as an ebb and flow system is usually comprised of a bed of soilless media through which nutrient solution is periodically flooded, then drained via gravity back to a tank for re-use. The frequency of ebb and flood cycles depends on a range of factors such as plant size, temperature etc.

Fig. 22 Simple hydroponic ebb and flood systems which are being used as part of a Masters project to investigate the optimal depth of growing media; a) the experimental units side by side, each has a different depth of growing media (the brown expanded clay pebbles) and b) the impressive root growth obtained in one of the treatments.

Greenleaf Nursery

The next activity for the day is a visit to a large ornamental plant nursery, and it’s a two hour road trip across the border into Oklahoma. The drive takes us through the forested, hilly terrain of the Ozark region and its’ spectacular scenery. We are accompanied by Dr Evans and his colleague Dr Garry McDonald, an assistant professor specialising in urban horticulture, sustainable landscape design, water quality and conservation.

The Greenleaf Nursery Company is one of America’s largest wholesale ornamental plant growers producing many millions of container plants annually, for sale to retailers, wholesalers and landscapers across the US and Canada. The Company has four large nurseries in three states and we are headed to the Parkhill site which is situated about 1 hour south east of Tulsa. As we pull into the main driveway the nursery sprawls out around us. It’s mind-bogglingly large, covering about 600 acres and employing 650 staff. This nursery is dedicated to the production of container trees and shrubs and produces 10 million liners* and 6 million

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finished plants per year (fig. 23). They grow 58 varieties of conifer, 901 varieties of broadleaf evergreen and deciduous shrubs and 170 varieties of flowering and shade trees.

We arrive at the height of their busiest period and the place is a hub of activity, with row upon row of massive HGVs being loaded with trolleys of trees and shrubs. As the site is so big and busy we are taken on a minibus tour guided by the site manager. Unfortunately there isn’t time to get out and walk about so opportunities for photographs are limited. There are hundreds of poly-tunnels here and these are divided into sections, each section containing a group of 10 or so tunnels over-seen by a section manager.

The nursery was established in 1945 as a much smaller concern on hilly, forested terrain. It’s located on the edge of Tenkiller Lake, a large reservoir fed by the Illinois River. As the nursery has grown, it has had to find innovative ways to source the large amounts of water required for its’ irrigation systems. Much of the water needs to be moved uphill so the nursery has built its own reservoir and pumping stations which are conveniently fed by the nearby lake. However, being situated above a lake prized for its clean water and trout population has created some environmental issues for the nursery. The production of 13 million plants annually means huge quantities of fertilizers are required and some of these inevitably end up running off the site and into the groundwater system. In order to avoid lawsuits, the nursery has had to install a run-off capture system to prevent polluted water being returned directly to the lake. This consists of a massive holding tank, where settling out of nutrient laden sediment can occur. Water is then returned gradually to the lake where any remaining nutrients are diluted to levels unlikely to cause harm. It’s a massive investment and indicates just how much pressure the US government is putting on business to improve water quality. It’s an issue that’s becoming more important to growers in the UK as well, particularly with an increasing amount of legislation from the EU on water quality.

*Professional nurseries sell plants on at various stages of development from newly propagated cuttings to large finished plants. Liners are young or immature plants usually perennial or woody type material which are typically sold for finishing to other nurseries. They usually require one or more growth seasons to reach a saleable size for the retail market and are most often sold as 9cm pots.

Fig. 23 A view over the nursery, it was an extremely large site with poly-tunnels as far as the eye could see.

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Ozark All Seasons

It’s back into the car, and after a quick lunch en route we cross back into Arkansas for our next nursery visit. This time we are going to see a business at the opposite end of the size scale - a small family run salad producer.

The nursery is located on a small farm, and was set-up in 2013 by a husband and wife team who had previously established a successful hydroponic salad business in the Western Caribbean. They had returned to the US to retire and had set-up the nursery as an experiment into sustainable, low carbon salad production. However, their experiment proved so successful that they decided to turn it into a business and the Ozark All Seasons salad company was born.

As we arrive outside a modest glasshouse, we are greeted by a couple of extremely friendly dogs and the owner of the company, Val. This set-up couldn’t be more different from the mornings visit to Greenleaf. There is just one greenhouse here, it is a prototype design and all the energy required is supplied by green technology. The structure is cooled geothermally in the summer and heated with a solar power in the winter. The building is designed to have the lowest carbon footprint possible and is still a work in progress. As we enter there is an impressive array of hydroponically grown lettuce and herb varieties on display (Fig 24a, b & c). Glancing down the length of the greenhouse, I feel as though I’ve slipped into some hopeful vision of the future. Val explains that his earlier career in US corporate agriculture lead him to question the impact conventional methods of food production were having on the environment and human health. This led him to investigate novel production systems with an emphasis on green energy and the minimal use of synthetic chemicals. He’s very passionate about this work and I can’t help getting caught up in his enthusiasm as the tour progresses.

He favours the NFT hydroponic system because it uses a fraction of the fertilizers and water of conventional field grown systems with no run-off. He actually uses a combination of organic and inorganic nutrients in the fertigation system as he believes this creates healthier more nutrient dense produce. As the environment is carefully controlled, no synthetic chemicals are required for pest and disease control, with biological control used instead where necessary.

The nurseries main customers are trendy Fayetteville restaurants who like to serve young heads of fancy lettuce varieties. More recently, the nursery has capitalised on a food trend which has promoted the health benefits of ‘microgreens’ (fig. 24d). These are 7-16 day old salads and greens which are eaten for their high concentration of beneficial nutrients and minerals. This small business has clearly found a niche market providing specialist produce to an ever growing population obsessed with the latest crazes in healthy eating. The great thing about this prototype system is that once set-up it’s cheap to run and can be modified to grow any number of fruits, vegetables and salads. It perhaps represents a new approach to the production of food which focuses on the sustainability of production methods and the quality of the produce. In urban areas of the UK, particularly in the south east, where space is increasingly at a premium but populations are very large, I wonder whether systems like this are part of the solution to supplying people with fresh, healthy produce. This visit has certainly generated a lot of conversation (fig. 24e) and fired up my imagination.

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Fig. 24 Images from Ozark all seasons; a) view across the glasshouse showing hydroponic salad production, b) newly planted seedling lettuce, c) lettuce heads approaching harvest, d) modified microgreen propagation channels containing mixtures of young plants ready for harvest and e) the visit sparked much conversation with (from left) Paul Alexander, Val the owner, Neil Bragg, Dr Evans and Dr MacDonald.

a) b)

c)

d)

e)

N. Bragg /Bulrush

P. Alexander/RHS

P. Alexander/RHS

P. Alexander/RHS

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It’s been an exhausting but inspiring day and it’s a scenic drive back before discussing the day’s highlights over a dinner of fried chicken with Dr MacDonald and Dr Evans.

25th The Compton Gardens and Crystal Bridges museum of American art.

It’s our last day in the US and a Saturday, but Dr Evans kindly offers to take us on a tour of some of the horticultural highlights of the area. It’s a gloriously hot, sunny day and with no sign of any tornadoes brewing - a perfect way to round off the study tour.

Compton Gardens

This is a 3.6 acre public garden dedicated to showcasing the native plants of the Ozark region. We are met at the entrance by the director of Horticulture, Corrin Troutman, a UA horticulture graduate. She’s clearly very passionate about her work and kindly gives us an extensive tour of the garden. The site was originally the home of a local man Dr Neil Compton, who was a physician and naturalist with a passion for the region’s native flora. He was also an advocate of conserving the floristic diversity of the area and successfully led a campaign to prevent the damming of the nearby Buffalo River. Had this project gone ahead it would have destroyed a very large area of natural habitat. It’s an extensive tour and we see a huge variety of native plants species which are all carefully labelled. There are a mixture of plantings including wooded glades, river banks, rock gardens and a reconstructed area of wild prairie. This is my kind of garden, it has a wild feel with lots of hidden shady corners where you can feel as if you have the place to yourself (fig. 25a,b). Its surprising cool under the dense canopy of native trees some of which are huge and have clearly been around a long time (fig 25c). It’s great to see a garden dedicated to native plants (fig. 25d), I don’t think I’ve been in one quite like it before. This garden also serves a clear educational purpose (fig 25e) and we see many adverts for events at the entrance. It’s a fantastic place for local people and the perfect escape from the noise and bustle of the city.

a)

b)

N. Bragg /Bulrush

P. Alexander/RHS

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Fig. 25 Images taken at Compton gardens which is dedicated to conserving the native plant species of the Ozark region; a) a natural wooded glade, b) paths snake through woodland with native plant ground cover, c) the old wizened trunks of trees provide a beautiful contrast to the colourful Azaleas below d) a bed of Senecia aureus ‘golden ragwort’ and d) the garden serves a clear education purpose with much information for the public on the benefits of utilising native plant species in their own gardens

Crystal bridges Museum of American Art

I’m quite reluctant to leave the cool, peaceful surroundings of the Compton Gardens, but it’s on to the Crystal Bridges Museum of American Art. The museum was founded in 2011 by Alice Walton, the daughter of the founder of Walmart and head of one of the richest families in the World. The museum itself is an enormous, modern building which houses more than $500 million worth of paintings and sculptures by some very famous names. The museum is set in large grounds which have been immaculately landscaped and range from perfectly kept lawns to forested glades.

c) d)

e)

N. Bragg /Bulrush

P. Alexander/RHS

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Dr Evans has arranged a tour of the gardens with Cody George, the museums field horticulturalist and also a UA horticultural graduate. Cody explains that the garden around the museum and wider grounds are designed to complement the modern, curved structure of the museum. The more formal areas immediately around the museum consists of about 10 acres of landscaped beds and 9 acres of turf (fig 26a). This area then merges into the wider grounds which comprise about 96 hectares of informal wooded landscaping. The garden is meant to be an extension of the museum complex and has been designed around four central themes art, education, architecture and nature (fig 26b). These themes resonant throughout the grounds with the addition of sculptures, sympathetically placed walls, seating areas and signage. The garden, looks very natural, but this is deceptive. Cody tells us that they have planted over 48,000 plant cultivars since the museum opened, including 490 taxa of trees. A minimalist approach has been taken to the landscaping and plantings are designed to complement and merge into the existing natural vegetation (fig 26d). The more formal planting scheme around the museum building is designed to provide colour and interest all year round with an emphasis on increasing the biodiversity of beneficial insects like bees and butterflies. There is also a natural spring present on the site which has been carefully managed to create a central water feature comprised of interconnecting pools (fig 26c). The water is incredibly clear and like a mirror perfectly reflects the colours of the carefully selected plantings around it. The museum building is also cleverly integrated into the surrounding gardens with the use of green walls (fig 26f) and a green roof (fig 26e).

a)

b)

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Fig. 26 Images taken during a tour of the Crystal Bridges museum of American art gardens; a) A formal area of lawn incorporating modern sculpture, b) the museum is designed to nestle into the native woodland, c) clever use of the spring to create a stream up to the museum entrance, d) inside the museum complex, the grey of the building contrasts beautifully with the surrounding woodland, f) a green wall on one side of the museum creates the allusion that the walls are a natural extension of the planting scheme and e) a green roof also designed to help the building merge into the surrounding garden but looking a bit worse for wear.

a)

c) d)

e)

f)

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Summary and conclusions of visit to Arkansas

This trip gave us an interesting insight into the involvement of business in the funding of horticultural science. The projects being carried out by Dr Evans and his team have a clear commercial angle but at the same time produce high quality academic publications. I wonder if UK scientists need to be less reluctant to collaborate with industry and embrace a more business oriented approach to research.

The UA takes an innovative approach to horticultural science education and I was impressed by the way in which conventional teaching is carried out alongside internships where students can gain practical experience in the horticultural industry. This approach clearly works and many of the department’s graduates have been successful in securing jobs in the Industry which is clearly thriving in and around Fayetteville.

It was also interesting to see the way in which horticulture is incorporated into many aspects of city life, from municipal plantings through to public gardens. There is a clear investment in greening of the city by the local authority, university and big business in the area.

Final summary

More than anything else this trip has is opened my eyes to the sheer scale of possibility that exists within horticultural science. It’s such a diverse field with so many challenges and so much potential for innovation. For my own personal development as a scientist it has been an excellent opportunity to show case my research and talk about the RHS-AHDB fellowship project. Many of the fundamental challenges in growing media science are the same for both the US and UK researchers and I’ve learned a great deal from seeing the approach to experimental work in the US. As a junior scientist, relatively new to the field, this trip as allowed me access to a network of new contacts with a huge wealth of knowledge and experience. I am confident this will help me as I develop my career beyond the fellowship.

The visit that really sticks in my mind is the one to Ozark all seasons, the small hydroponic salad grower. Here is a grower, who despite the financial risk has dared to try something new in a bid to improve the sustainability of his operation. This sort of innovation in horticultural practice would not have been possible unless the grower had a sound understanding of the science of hydroponic growing. This has come about through a clear and consistent dialogue with researchers who can communicate their science in a language the growers can understand.

It’s an important lesson; regardless of who our audience is professional or amateur, it’s a scientist’s job to ensure we equip growers with the information they need to grow better.

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Summary of expenditure

TRAVEL

Air fare from London to US (including Internal transfers) £770.03

Transport to/from airport £11.40

Total Travel Costs £781.43

ADMINISTARTION

Travel Insurance £45.16

Permits (ESTA) £10.00

Total Administration costs £55.16

SUBSISTENCE

Accommodation (8 nights bed and breakfast) £796.65

Food/stores £144.46

Total Subsistence costs £941.11

GRAND TOTAL £1,777.70

Signed: (G.E. Barrett, bursary recipient)

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Acknowledgements

I am extremely grateful to the RHS Bursaries committee and the RHS Coke Bursary Trust for making this trip possible.

I would also like to thank those who encouraged me to apply and supported my application including from the RHS; Alistair Griffiths, Paul Alexander, John David, Tim Upson and Mandeep Matharu and from the AHDB – Horticulture, Jon Knight.

A huge thank you to our hosts Dr Jackson and Dr Fonteno at NCSU and Dr Evans and Dr MacDonald at the UA who arranged such a wonderful itinerary for us. Not only did they share openly their research but were also such great company, introducing us to all manner of new culinary experiences!

Finally, I would like to thank my two travel companions and fellowship mentors Paul Alexander (right) and Neil Bragg (left). Thank you for donating your photographs for use in this report - such better quality than most of mine!

Most of all I’d like to thank you both for all your encouragement and support over the last few years………Australia anyone?

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References

1. Judd, L.A., Jackson, B.E. and Fonteno, W.C. 2015. Rhizometer: An apparatus to observe and measure root growth and its effect of container substrate physical properties over time. HortScience, 50: 288-294

2. Jackson, B.E. 2009. Back to the Grind: Pine tree substrate encourages prolific root growth in container plants. Nursery management and Production, September 2009: 28-34

3. Jackson, B.E., Wright, R.D. and Barnes, M.C. 2010. Methods of constructing a pine tree substrate from various wood particle sizes, organic amendments and sand for desired physical properties and plant growth. HortScience, 45:103-112

4. Fonteno W.C., C.T. Harden and J.P Brewster. 2003. Procedures for determining physical & hydraulic properties of horticultural substrates. Horticultural substrates laboratory. North Carolina State University, Rayleigh, NC

5. Handreck, K.A. 2011. Container media: the Australian experience. Acta Hort. 891: 287-295

6. Evans, M.R. and Gachukia, M. 2004. Fresh parboiled rice hulls serve as an alternative to perlite in greenhouse crop substrates. HortScience, 39:232-235

7. Evans, M.R. and Gachukia, M.M. 2007. Physical properties of sphagnum peat-based root substrates amended with perlite or parboiled fresh rice hulls. HortTechnology, 17:312-315

8. Evans, M.R. 2004. Processed poultry feather fiber as an alternative to peat in greenhouse crops substrates. HortTechology, 14:176-179

9. Evans, M.R. and Vance, L. 2007. Physical properties of processed poultry feather fiber-containing greenhouse root substrates. HortTechnology, 17:301-304

Useful links

North Carolina visit

Dr Brian Jackson’s website:

http://www.ncsu.edu/project/woodsubstrates/

JC Raulston Arboretum website:

http://jcra.ncsu.edu/

Mulch and soil Council USA:

http://www.mulchandsoilcouncil.org/

North Carolina State farmer’s market in Rayleigh:

http://www.ncagr.gov/markets/facilities/markets/raleigh/

Old Castle Lawn & garden:

http://www.myoldcastle.com/Products/Lawn_and_Garden/index.htm

Pacific Organics:

http://www.pacific-organics.com/

The NCSU Horticultural substrate laboratory website:

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http://www.ncsu.edu/project/hortsublab/intro/index.html

The UK growing media association:

http://www.growingmedia.co.uk/

Arkansas Visit

ACCEPtS course in greenhouse management:

http://accepts.uark.edu/courses/greenhouse-management.html

Compton gardens website:

http://www.comptongardens.org

Crystal bridges Museum of American Art website:

http://crystalbridges.org/

Greenleaf Nursery:

http://greenleafnursery.com

Growstones:

http://www.growstone.com/wp-content/uploads/2013/05/Growstone101-Hydro.pdf

Ozark All Seasons:

http://ozarkallseasons.com/

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Appendix

PowerPoint slides for talk given at North Carolina State University and the University of Arkansas

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