Hydroponic Living Walls – DYI – Really?

Over the years I haven’t done particularly good job writing about hydroponic based technology,

more specifically hydroponic green walls. I would contribute that to the fact beyond the ever popular

Patrick Blanc the technology was still being developed for vertical walls. I personally found them a

cumbersome maintenance project; however there are advances in materials and easy applications but

not without a “fine line” between success and failure. I’m going to share some of my experiences and

explain that “fine line” that includes the detailed variables. Like green walls in general hydroponic

techniques are not new, the Greek terms “Hydro” means water & “Ponic” is labor. Even the gardens of

Babylon had a pumping system to bring water to the top of the garden letting it trickle back to the lower

pools. Nature irrigates naturally occurring walls through runoff that collect nutrients from the natural

decomposition to feed the plants clinging to the side of cliffs and walls. In a previous article (ENTER

DATE OR LINK) I described the origin of green walls and the natural rock faces created by Mother

Nature. Nutrients & minerals are created naturally, picked up by runoff as the roots are bathed in a

nutrient rich solution. Sounds simple right? Not so fast! We’re talking about Mother Nature here.

I have documented and studied naturally occurring

green walls over the years. Since I live in upstate New York

(USA) I am much more adapt to the native plant types

locally except for my time spend outside of Portland Oregon

hiking to Multnomah, Latourell, Wahkeena and Horsetail

waterfalls along the Columbia River. The walls I have studied

are the epitome of “Native Living Walls”. Before I continue

let me make reference to the nomenclature of “Green

Walls” as a general term which is divided into “Green

Facades” and “Living Walls”. Since living walls are defined by

having the root system throughout the wall, naturally occurring green walls are defined as living walls. A

green façade is usually a 3d trellis like support structure with a climbing plant found at the base. In

nature climbing plants are also naturally occurring however for the purpose of this article our focus is

living walls.

Although my hiking has decreased to almost none over the past year due to knee surgeries the naturally

occurring living walls provide a spectacle only found in nature. Plants we see as common or to the

untrained eye seem like nothing more than moss & ferns. A close look displays an awesome range of

colors and textures, to the touch on a hot summer day the walls are cooling and provide a haven for

Top Right: Mile marker to various

trails along the Columbia River Gorge.

Left: Living Wall by Mother Nature

along the Larch Mountain trail OR,

consisting of various native plants

including various lichen & ferns.

animals & insects of all kinds. Every wall I have seen up-close has contained a variety of liverworts, ferns,

mushrooms, lichens and wild flowers.

The pictures provide just a small sample of what can be found growing on the natural living walls.

Without the use of synthetic fertilizers this is natural hydroponics at its best.

Trying to duplicate Mother Nature’s efforts is no easy task. In

nature plants adapt and are conducive to the environment, they are

naturally at home. Installing a hydroponic living wall is relatively easy;

the challenge is to meet all the needs of a plant pallet that is part of the

man made ecosystem, totally unnatural and more times than not

combining plants that are not of the same needs is the main reason for

failures. Hydroponic living walls are also much different than the

traditional horizontal technology developed to grow food. For starters

the living walls are vertical unlike food producing units that are

horizontal, even if they are “stacked” as towers and allow the

vegetation to climb vertical (Green Façade). Before we talk about the

materials and “How to” part, start with the types of hydroponic

systems available. There are active and passive hydroponic systems,

easily remembered because “active” means with a mechanical pump (which is the common for

hydroponic living walls) is moving water that is infused with chemical nutrients as it passes over the

roots. A passive system works without a pump and utilizes a wicking fabric or some type of inorganic

media that that draws water to the roots. The green wall systems I have had the opportunity to trial and

work with have a combination of materials, everything from felt, to cleaning scrub pads, plastic, poly

vinyl chloride (PVC) and coco husk and they all rely on a mechanical means (Active system). I have not

found one single combination of products and techniques that make hydroponic green walls a fool proof

method. Some are much more successful than others but not without attention to detail and intensive

maintenance requirements. In a natural occurring living wall the plants that are native to the

From Left to Right: Anomodon attenuatus (anomodon moss), Atrichum undulatum, Dicranum fulvum

(dicranum moss) & Hart's-tongue fern (Asplenium scolopendrium)* this fern is on the New York State

Threatened List and the majority can be found in New York State. Below from Left to Right: Wild

Columbine & Winterberry, Sedum spathulifolium (Oregon) is a favorite food for the Pika (A small

relation to the Rabbit). In the spring look for a bright yellow flower that stands out against the lichen.

surroundings are adapt to the conditions. “Conditions” refer to elevation, lighting, nutrient availability

and in nature only plants that are adapt to the present conditions will continue to thrive. In the living

wall the task of plant survival is put on the installer, system type and the expertise of the maintenance

technician. Just because you are a landscaper or interior plant company don’t assume you’re going to be

able to jump right in and master hydroponic living walls, there is a learning curve. I do have relations in

the industry, some of them national companies; they maintain both media /soil based walls and other

hydroponic walls. The maintenance on the hydroponic walls is a break even for them because of the

higher than average maintenance needs. The variables and conditions are ever change and having the

ability to meet the maintenance needs and upkeep is an education only experience can bring. There is

that “fine line” between success and failure. Many variables are under constant monitoring in order to

be successful. Hydroponic living walls are seldom 100% lush and thriving all the time because of the ever

changing variables with very little room for error. Even a slight change in temperature can disrupt the

dynamics of the wall causing massive areas of die off; we will talk more on monitoring the walls later.

Hydroponic Living Wall: Basics

Hydroponics requires many variables to come together in sync in order for it to be successful.

My own reading suggests that experience and education are a must before diving into hydroponic

growing. For the most part, common landscapers and indoor plant companies are usually not at the

level of expertise when they decide to either install or take on the maintenance of hydroponic living

wall. Medias / root support structures, clean water, temperatures, Ph levels, lighting, nutrient solutions,

and oxygen exchange, (oxygen to nutrient ratios) are part of the synchronization of successful

hydroponic walls. Hydroponic living walls start with some type of waterproofing to protect the structure

behind the wall. There are common water proofing membranes, peel and stick applications, PVC sheets

or in some cases I have seen layers of felt stapled directly to a concrete wall.

Felt fabrics, coco husk and porous sheets of scrub pads & porous foam are the most popular of

materials. There are many varieties of applications for each of these products, again I’m not partial to

one particular material and I have seen various results with some better than others.

http://www.therange.co.uk

Top Left: Hydroponic Capillary Mat

Top Right: Felt Fabric

Right: Capillary Fabric with plastic lining and

geo-textile backing (Manufacturer unknown)

Right: Nedlaw Hydroponic Living Wall

constructed from 2 layers of similar 3M

Doodlebug scrub pads in larger rolls prior to

being cut.

Above: 3M Doodlebug close up, 56” wide,

by 42 yards long @ $32 per yard

Purchase Information Contact:

Joe Koszarek, Beacon Lighthouse Inc

jkoszarek@beaconwf.com

Top Left: Polyester weave. (Manufacturer unknown)

Top: Coco Husk block inserted into a geo-textile bag by GSky.

Bottom Left: Open Cell Polymer Foam Blocks similar use by

Eco-Walls Purchase Information Contac: Chi Meng

http://www.chimeng.com.tw

Deciding on what fabric or media to use can only come through experience. Personally I have

documented and found high amounts of root and crown rot in all the media types shown here.

According to Wikipedia, “In hydroponic systems inside greenhouses, where extensive monocultures of

plants are maintained in plant nutrient solution (containing nitrogen, potassium, phosphate, and

micronutrients) that is continuously recirculated to the crop, Pythium spp. cause extensive and

devastating root rot and is often difficult to prevent or control.[1][4][5][6] Root rot can occur in hydroponic

applications, if the water is not properly aerated. The root rot affects entire operations two to four days

due to the inherent nature of hydroponic systems where roots are nakedly exposed to the water

medium, in which the zoospores can move freely.[4][5][6]” (http://en.wikipedia.org/wiki/Pythium)

It is typical that root rot is the result of an anaerobic environment. (As we continue I will explain the

importance of balancing nutrients and oxygen exchange.) Other factors include: unsterilized tools and

equipment, unfiltered water, dead roots and leaves, other infected plant material. As a former

landscape contractor I know personally what it would take to sterilize my tools to work on such a wall

frankly it may be too much trouble. This is one of the reasons the cost of maintenance is high. The

preventative labor is equal to the actual labor pruning and replacing plants.

Left: Hydroponic Living Wall showing signs

of both crown and root rot.

Symptoms include leaf drop, yellowing &

discoloration.

Root rot evident sandwiched between two

layers of 3M Doodlebug.

Distinct onset of root rot, this particular

plant will last another 24-72 hours.

Because of the constant presence of water, hydroponic living wall medias tend to be a breeding

ground for algae and gnats. Keeping the plants healthy, vigorous and stress-free is the best "cure"

against pythium. Pythium is almost impossible to 100% eradicate from an infected system; this involves

starting completely over with new plants, containers, equipment, etc.

Left: Hydroponic Living Wall utilizing open

cell foam showing plant loss due to crown

and root rot.

Middle: Obvious signs of yellow and

discolored leaves, Leaf loss and plant

deterioration.

Bottom: This hydroponic living wall shows a

variety of symptoms that include: Root rot,

discoloration, crown rot and algae build up.

If you look close you will see some naturally

formed lichen and the burnt tips of the

leaves may be caused by salt build up or

over fertilizing.

To remedy the wall you will have to disinfect the entire system. Manually scrub and bleach

might be necessary, add tap water, and disinfect the water with strong h2o2. The solution will require

100ppm to kill pythium, however this can also kill small plants. Wait 24 hours for h2o2 to dissipate to a

safe level; do not add more water to system! Add only h2o2-treated water, add nutrients and beneficial

enzymes. The aerobic-loving enzymes will colonize the sterilized medium and system, hopefully

displacing any of the anaerobic bacteria. Start with a clean system is the best prevention. Below you can

see leaf build up at the drain (Right) and fallen leaves rotting on the left. These dead leaves become food

for the Pythium. This is also true with algae. Algae will eventually dry, die and become organic material

fueling Pythium fungus. Once started it becomes a vicious cycle without sterilizing the entire wall. There

are chemical / biological preventatives I would suggest going to talk with your local hydroponic store.

Once you decide on a rooting media, having clean water is not an option. Some professional

growers will use distilled water, this is much more expensive however hydroponics are very sensitive to

salts, Ph and changing variables including temperature. The water is a vehicle that transports a nutrient

solution to the top of the wall via a pumping system and allows it to saturate the rooting media via

gravity from the top down while bathing the roots. All plants need key macronutrients: Nitrogen,

Phosphorus and Potassium lead the list of “must have” chemicals.

Nitrogen (N) promotes vegetative growth

Phosphorus (P)—contributes to healthy roots and flower blooms

Potassium (K)—important to fight off disease and resistance to pests

Sulfur (S)—Health and improved color of the leaves

Calcium (Ca)--promotes new root growth

Magnesium (Mg)--chlorophyll, contains a Mg ion that improves food production

In commercial fertilizers the N, P & K are depicted by numbers in ratio to the weight of each one. For

example 10-10-10 is a balanced ratio of N, P & K. 25-5-5 will provide a quick rapid greening of the visual

leafy portion of the plant with only 1/5th the P & K. Boron (B), copper (Cu), cobalt (Co), iron (Fe)

manganese (Mn), molybdenum (Mo), and zinc (Zn) are micronutrients responsible for a myriad of tasks

including: Cell wall development, nitrogen and sugar metabolism, protein synthesis and water loss just

to name a few. Vegetation acquires these micronutrients directly from natural growing media;

commercial producers of fertilizer do not include them for typical landscape and crop applications, but

because the hydroponic technologies for living walls do not include a growing media that can hold

nutrients the nutrient solution MUST include these essential micronutrients.

This is where inexperience becomes costly. If you are not trained nor have experience with vegetation

for hydroponic living walls the risk may outweigh the glory. This is not a project you want to experiment

with a client. You risk reputation and serious monetary loss simply through maintenance and plant

replacement. I mentioned earlier we work with a very experienced indoor plant company who is happy

to break even on the maintenance of the hydroponic living walls they maintain. They keep the wall as

part of the overall maintenance account for the building. There are many over the counter pre mixed

nutrient solutions contact your local hydroponic supplier for more details.

Once you add plants the variables will continue to grow from here, no pun of course. You have

to find a balance between nutrient solutions, pH levels, temperatures, lighting, and dissolved oxygen. All

of these variables must be in alignment for a hydroponic living wall to work.

pH is a scale from 1 to 14 that measures acid-to-alkaline balance. One being the most acidic, 7 is

neutral and 14 is most alkaline. Every full point change in pH represents a 10-time increase or decrease

in acidity or alkalinity. For example, soil or water with a pH of 5 is 10 times more acid than water or soil

with a pH of 6. Water with a pH of 5 is 100 times more acidic than water with a pH of 7. With a 10-fold

difference between each point on the scale, accurate measurement and control is essential to a strong

healthy garden.

Most plants grow best with a pH between 6.5 - 7. Within this range, plants can will absorb and

process available nutrients most efficiently. If the pH is too low (acidic), salts bind nutrients chemically,

and the roots are unable to absorb them the plants won’t feed. An alkaline soil with a high pH causes

nutrients to become unavailable. Toxic salt build up that limits water intake by roots also becomes a

problem, get to know your water. Hydroponic solutions perform best in a pH range a little lower than

for soil. The ideal pH range for hydroponics is from 5.8 6.8, slightly acidic. A bi weekly test should be part

of the maintenance process, adding products like pH up (potassium hydroxide and potassium carbonate)

and pH down (Phosphoric acid), add cost to maintain the hydroponic living walls.

Water temperatures:

The amount of dissolved oxygen in a nutrient solution depends on the water temperature. Cold water

can 'hold' more dissolved oxygen. A fully aerated solution at 20C/68 F is 9 - 10ppm; at 30C/86F it's

7ppm. According to Dr Lynette Morgan the Director of Research at SUNTEC International Hydroponic

Consultants, based in Manawatu, New Zealand, Root oxygen requirements double for each 10C rise in

root system temperature (max 30C/86F). The dilemma for the maintenance technician is that with a 10C

rise in temperature, root system oxygen requirements will double, while the oxygen carrying capacity of

the solution will drop by over 25%! The nutrient dissolved oxygen is unable to supply the root's oxygen

demands, leading to prolonged oxygen starvation. Oxygen starvation will result in slow growth, mineral

deficiencies and root die-back. Oxygen starvation will stress the plant, leading to an eventual attack by

opportunistic pathogens, such as ever-present pythium aka root rot. What Dr. Morgan is describing is

the anaerobic environment that is naturally occurring is hydroponic systems.

Equipment & Set Up:

For the most part the equipment needs are pretty simple. Assuming we are talking specifically

about hydroponic green walls Im not going to talk about ebb & flow or aeroponics, specifically we are

utilizing a top feed configuration; water solution is pumped up and allowed to drip through the media

back to a reservoir. Pending the size of your wall, freestanding or wall mounted you need a reservoir,

pump, inorganic media (what will physically hold the plants), test kits and sterile tools.

For a reservoir the basic of plastic containers will work fine pending on the size of your wall.

Some more advanced applications also contribute to the cosmetics of the system, stainless steel and

decorative pools are not uncommon but because of the sensitivity of the solution the exposed reservoir

is subject to becoming a catch all for garbage or debris immediately altering the dynamics of the pH, as a

word of caution take careful consideration to your reservoir it is the life line to the success of the wall.

For larger walls & walls exposed to evaporation a fill float can be retro fitted to the reservoir. The color

of your reservoir will also play a part in the water temperatures. As we discussed earlier higher water

temps result in less oxygen!

There are also a variety of pumps available, my experience as a pond builder would lead me to

the magnetic drive types that seem to last over continuous use. When choosing a pump the key is to

understand how much water you need to pump at what rate and the height you have to pump it. The

key here is what we call the “Head Height” or maximum height the pump can push water. Head is

measured in length and the pump capability of flow vs height. For example, the height from the top of

the reservoir to the top of the wall is 10 feet. Searching the internet we find literally thousands of

options. A statistical rule is to double the PSI (pound per square inch) to determine the head in which

the pump will pump zero GPH (Gallons per hour).

Table one shows the actual “Head Height” taking in to account the reservoir is not part of the

calculation. The equal distribution of water going through the pump through the supply tube while it is

in the water is equal to the water weight outside the tube until it exits the reservoir when gravity and

the actual weight of the water in the tube come into play when configuring the actual pressure needed

to reach the maximum height. Table 2 is a common and easy means in which you can determine the

minimal needs would be to reach the height needed to irrigate your wall.

Head Height

Reservoir, No Head Pressure Here

Wall

Table 2

www.pondworld.com

Table 1

The life line of the system can be viewed as if it were a human. The pump is the heart, the tubes

are veins and arteries, and the solution is the blood carrying nutrients to the remainder of the body all

must be in working order.

Constructing Your Hydroponic Living Wall

For the most part the steps are simple. Start with deciding on an area with good light and

recirculation air flow. I have seen various types of armatures that on angles off the wall so we end up

with about six inches from the bottom of the wall. Fig1. In most cases the walls are flat at a true 90

degrees. The angle however will prevent the irrigation water from dripping off the leaves allowing it to

follow the angle of the rooting media.

The following sequences of pictures are from Peter Kastan and provide a real hydroponic wall

installation. You can visit Peter at http://junglewallsmiami.com

Step 1 Armature and Mounting Framework

Figure 1 6”

Support

Wall

Vegetation

Water Flow

Step 2 Mounting the PVC sheets (Purchase at Home Depot) 15 – 3 f2 sections @ $39.96

Step 3 Mounting the Rooting Media (Geo – textile, open cell foam, coco husk, Doodlebug Rolls)

Rooting Media Complete Partial Plant Installation

There is a lot more to hydroponics than a simple pump and solution to feed the plants. Living

walls are not for the faint of heart when it comes to experimenting with someone else’s investment. My

advice is to try various materials that are locally available, get advice from your local hydroponic supplier

and set up your own trials and research. I have pointed out the variables that will determine your

project a success or a maintenance catastrophe. There is much more to the hydroponic living walls, I

have only scratched the surface to the highly advanced systems and applications.