Forcing GuideForcing GuideForcing GuideForcing Guide / The Lily / The Lily / The Lily / The Lily

1. Storage ................................................................................................................................2 2. Greenhouse and greenhouse equipment ...............................................................................3

3. Soil and irrigation water....................................................................................................... 6 4. General cultivation procedures ............................................................................................ 8 5. Greenhouse environment.................................................................................................... 12 6. Other cultivation systems ................................................................................................... 14

7. Harvesting and post harvest treatment ................................................................................ 18 8. Planning and labour ...........................................................................................................20 9. Crop protection and disease control.................................................................................... 21 10. Selection of cultivars ........................................................................................................28

1. Storage1. Storage1. Storage1. Storage To ensure satisfactory long term storage of lilies, frozen lilies should be packed in plastic film

plus slightly moist peat or potting compost. Lilies delivered in a frozen state can continue to be stored, provided this is done at the right temperature. It is still possible to freeze newly harvested bulbs not delivered in a frozen state up to the 15th of January. Lilies which were previously frozen cannot be re-frozen as frost damage will certainly occur but the degree of damage depends on

the type of cultivar, time of the year and the length of time unfrozen. During the freezing process bulbs, irrespective of where they are located in the box or stack, must

be frozen to the right temperature in a relatively short space of time (7 to 10 days). The cold store should therefore meet a number of requirements. In the Netherlands these are as follows:

• walls must have an insulation level of 0.3 Watt/m2/Kelvin

• the cold store must have a cooling capacity of 30-60 Watt per m3 cold store volume

• automatic, slow-speed ventilators must be installed

• there must be adequate space between the boxes/stacks of boxes in the cold store

• there must be consistent air circulation through-out the cold store. It is particularly important to maintain a uniform temperature throughout the entire cold store.

Minor differences in temperature can cause frost damage or shoots to develop. Bulbs are frozen and stored at the following store temperatures: Asiatic - 2.5°C Oriental - 1.5°C Longiflorum hybrids - 1.5°C L/A hybrids - 2.5°C

Bulbs of Asiatic hybrids can be stored for up to a year without showing any detorioration in quality. Bulbs stored for a longer period will develop more rapidly, plants will be smaller and fewer buds will develop.

Oriental and Longiflorum hybrids cannot be stored for such a long period. From July onwards, depending on seasonal conditions and the cultivar, there is a risk that storage problems, such as shoot formation and frost damage will occur.

Lilies which have not been frozen can only be stored for a short period. The storage duration depends on the storage temperature and the time of year. This means for example, that fresh bulbs can be stored longer in temperatures above freezing point during January and February than they can in the autumn. On average, bulbs can be stored at a temperature of approx. 1°C for a maximum of 2 weeks and at 5°C for a maximum of 1 week.

2. Greenhouse and greenhouse equipment2. Greenhouse and greenhouse equipment2. Greenhouse and greenhouse equipment2. Greenhouse and greenhouse equipment Greenhouse facilitiesGreenhouse facilitiesGreenhouse facilitiesGreenhouse facilities

For the cultivation of lilies it is essential to have the right greenhouse facilities. A suitable greenhouse environment must be maintained in spite of very changing conditions. Temperature, air circulation, ventilation and light must therefore be easy to adjust. Optimum climate control for

lilies can be achieved by choosing a greenhouse with an adequate air volume capacity, as this will also mean that there will be sufficient space in the greenhouse to install screening, irrigation and lighting equipment.

It is essential to have a greenhouse with good light penetration, especially during the light deficient months of winter. Poor light conditions increase the risk of bud drop and quality deterioration. During the remainder of the year, greenhouse ventilation is an important factor when lower soil and air temperatures are necessary.

Greenhouse equipment: Heating systemGreenhouse equipment: Heating systemGreenhouse equipment: Heating systemGreenhouse equipment: Heating system

In a large number of regions a heating system is essential. Asiatic hybrids and L/A hybrids require a minimum constant greenhouse temperature of 8°C to 14°C, while the other groups require a temperature of 16°C. The required norm for the heater system to achieve these temperatures is approximately 220

Watt per m2 per hour. Because of its superior heat distribution and climate control a pipe heating system is the best choice but air heating systems can also be used. It is important to ensure that these systems provide a satisfactory distribution of heat, have regular combustion and a leak-free outlet for combustion gases. If the heating system has not been properly adjusted, ethylene gas could escape into the greenhouse and cause bud drop. It is certainly possible to install a heating system by laying pipes or flexible hoses (temp. max 40°C) through the beds and this system is to

be recommended, bearing in mind the importance of maintaining a dry crop (Botrytis prevention). Greenhouse equipment: CO2 SystemGreenhouse equipment: CO2 SystemGreenhouse equipment: CO2 SystemGreenhouse equipment: CO2 System

It is advisable to enrich the atmosphere with CO2 because of the beneficial effect it has on the growth and flowering of lilies. The crop is sturdier, greener and there is less risk of bud drop. The gas is supplied from burners, from the central boiler or from pure CO2. The treatment is applied

as soon as it starts to get light in the morning and continues for a number of hours or even the whole day, provided all ventilators and doors of the greenhouse are closed or ventilation is kept to a minimum and there is sufficient light available for assimilation.

With assimilation lighting enrichment can continue for 24 hours. For proper control of CO2 it is necessary to regularly check the levels by using simple gauges. There must be optimum combustion to prevent damage to the crop by CO2 and ethylene, and a safety device is required to indicate any possible defects quickly.

Greenhouse equipment: Irrigation systemGreenhouse equipment: Irrigation systemGreenhouse equipment: Irrigation systemGreenhouse equipment: Irrigation system

The most important requirement of an irrigation system is even water distribution. It is essential that regular checks are carried out to ensure even distribution, including pre-planting. A lack of water or excess water results in uneven and slow development and growth, short plants and sometimes even bud desiccation in a few susceptible cultivars.

An overhead irrigation system is preferable as this provides even water distribution and also the ability to wash-off the crop. Furthermore, in low relative humidity conditions an overhead system cools the crop.

At a later cultivation stage, when growth is dense, a low level irrigation system or trickle hoses can be used to prevent tall, top-heavy plants from toppling, especially in winter. Furthermore the crop will remain drier, which will greatly reduce the risk of Botrytis. This is particularly important when growing cultivars susceptible to Botrytis and for crops grown in areas

of high relative humidity or at certain times of the year when relative humidity is high. An overhead irrigation system must meet a number of technical requirements:

• height of system should be between 1.60 to 2.15 m.

• distance between the irrigation pipes should be between 2.20 to 3.20 m.

• distance between sprinklers along the pipe should be at least 1.00 m.

• each sprinkler should provide approx. 4 liters of water a minute

• the sprinkling pressure should be 1.5 to 2 bars (kg/cm2)

• the water filtration should be 1 to 400 microns It is certainly not advisable to flood the soil during cultivation as this causes deterioration of the structure. Greenhouse Greenhouse Greenhouse Greenhouse equipment: Soil coolingequipment: Soil coolingequipment: Soil coolingequipment: Soil cooling

During periods of high temperatures, soil temperatures can be kept sufficiently low by soil cooling. Soil cooling can be used from planting until the formation of the stem roots. The cooling system consists of four tubilene hoses per bed laid at a depth of approx. 45 cm. The soil

temperature is adjusted to and maintained at the required temperature by using cooled or spring water. This results in better and more uniform growth, which gives longer and sturdier plants with more buds.

Greenhouse equipment: Lighting equipmentGreenhouse equipment: Lighting equipmentGreenhouse equipment: Lighting equipmentGreenhouse equipment: Lighting equipment Light affects the growth of lilies (assimilation) and their development, including flowering

(photoperiodicity). Depending on the time of year, the location of production in relation to the equator, the amount of light penetration in the greenhouse and the cultivar, assimilation lighting or day length lighting may be desirable or may even be essential.

Greenhouse equipment: Assimilation lightingGreenhouse equipment: Assimilation lightingGreenhouse equipment: Assimilation lightingGreenhouse equipment: Assimilation lighting Insufficient light (radiation) results in inadequate growth in plants and in lilies this manifests

itself in bud drop, a weaker crop, a lighter foliage color and a shorter vase-life. Lilies particularly need sufficient light for satisfactory development of flower buds. During the winter, in light deficient conditions, from the time flower buds reach the 1 cm - 2 cm stage up to harvesting, buds may turn white and fall off (bud drop).

The Asiatic hybrids are the most susceptible cultivars to bud drop, but there are large differences between cultivars. Longiflorum hybrids are clearly less susceptible and Oriental hybrids are the least susceptible.

For winter cultivation, depending on latitude and regional climate, growers must ensure satisfactory light admission in the greenhouse and not use a greenhouse which is shaded by its surroundings. Growers should also be aware of the fact that the use of screens, including screens

of plastic film, will cause a considerable loss of light penetration into the greenhouse.

Furthermore it is advisable to use during the winter months cultivars less susceptible to a lack of light and to plant bulbs wider apart. The minimum light density in the greenhouse for Asiatic hybrids is 300 wh/m2 or 190 Joules/cm2/day (PAR = Photo synthetically Active Radiation). However, should daylight need to

be supplemented with assimilation lighting this should begin from the 1 cm - 2 cm bud stage. The table sets out for each lily group the periods in which natural light is insufficient, the number of lighting hours needed per day and the cultivation phase during which assimilation lighting is

required. Usually assimilation lighting is provided by using one 400 Watt SON-T-lamp fitted with special reflectors per 10 m2. For additional information on these lamps, please consult your local information advisory service or your supplier.

Greenhouse equipment: Day length lightingGreenhouse equipment: Day length lightingGreenhouse equipment: Day length lightingGreenhouse equipment: Day length lighting

Light, in the form of day length, affects the flowering of the lily. Flowering can be brought forward (advanced) with some lily cultivars by artificially extending the day length during periods when days are short. Artificial extension of day length is only recommended for spring cultivation with new crop bulbs.

Used in autumn it will shorten the cultivation period but because of the fast development of lilies their stems will not be strong enough. The group of cultivars which benefits from extended daylength can be found among the Oriental

hybrids and are characterized by a cultivation period lasting more than 100 days for spring cultivation with fresh bulbs. From the time 50% of the shoots have emerged, lilies are exposed to daylength lasting up to 16 hours, continued for 6 weeks or until the flower buds in the closed inflorescence are just visible. Daylight extension, using light bulbs (with approx. 20 Watt/m2 installed power) is given immediately before natural daylight begins. It is also possible to use Cyclic lighting (10 minutes of light, 10 minutes of dark) but the results are less successful.

Daylight extension permits earlier marketing of Oriental hybrids which benefit from this treatment than other lilies in the spring. However they could be somewhat shorter and there is a greater risk of bud drop. When natural daylength lasts for 16 hours or longer there is really no point in providing day

length lighting as the benefits are so small. GreeGreeGreeGreenhouse equipment: Screening equipmentnhouse equipment: Screening equipmentnhouse equipment: Screening equipmentnhouse equipment: Screening equipment

From the viewpoint of climate control and for energy-saving in the winter it is advisable to use screening equipment. A mobile screen that does not exclude too much light is ideal. Particularly during spring, autumn and winter in the crop’s light sensitive phase it enables optimum use to be

made of natural light under poor light conditions. It is better to apply or install fixed shading in the form of a layer of chalk painted on the greenhouse roofing or shade cloths (preferably on the outside of the greenhouse) when light conditions remain above the minimum amount required.

Remove shading on time in the autumn. Fixed shading can also be used during the first three weeks after planting. Preferably use shades which allow humidity penetration.

3. Soil and irrigation water3. Soil and irrigation water3. Soil and irrigation water3. Soil and irrigation water SoilSoilSoilSoil

Lilies can be grown on almost all soils. It is however important that growers ensure that the soil used for the cultivation of lilies has a good structure throughout, particularly the top layer, and is also kept well-drained during the entire growing period. Heavy loam and clay soils are less

suitable for cultivation purposes but can certainly be used if humus retaining substrates are worked through the soil to a depth of 30 cm, as this will aerate the top soil while at the same time allowing sufficient quantities of oxygen to be retained in the soil water. Besides water and

nutrients, oxygen in the soil is also vital to plants for a good and healthy root system and therefore plant development. Surface panning of slake-sensitive soils can be prevented by applying a layer of rice straw, rice chaff, pine needles, peat compost et.

pHpHpHpH

Maintaining the correct pH (acidity) of the soil plays a major role in the root development of lilies and in the correct uptake of nutrients. If the pH is too low this will result in excess absorption of elements such as manganese, aluminium and iron, while a pH which is too high will result in an inadequate uptake of phosphorous, manganese and iron (see Nutrient deficiency) among other

nutrients. It is advisable to maintain a pH of 6 to 7 for the Asiatic, Longiflorum hybrid and L/A groups and a pH of 5.5 to 6.5 for the Oriental hybrids. To reduce pH levels, peat products should be worked through the top soil. When using fertilizers, it is advisable to use ammonium-based fertilizers and area, as these will also reduce pH le-vels. To increase pH levels work compounds containing lime or magnesium-based lime thoroughly through the soil before planting. In cases where the pH level has been extremely low, after liming,

it is advisable to wait at least one week before planting. During the growing period it is preferable to use fertilizers, such as nitrate-N fertilizers, which increase pH levels.

Water balanceWater balanceWater balanceWater balance The lily is not a deep rooting plant; it does however require a well-drained soil depth of at least 40 cm, especially considering that between crops it is often necessary to flood the soil because

of high salt levels. Salt sensitivitySalt sensitivitySalt sensitivitySalt sensitivity

The lily belongs to the group of salt susceptible plants; therefore high salt levels have an inhibitive effect on water absorption through the roots, which in turn will effect the stem length of the plant.

The salt level of the soil is influenced by three factors, namely: 1. the salt level of manure or fertilizer 2. the salt level of the irrigation water

3. the nutrient level of the previous crop Have a soil sample taken at least six weeks before bulbs are planted, to give sufficient information on the soil’s pH, the total salt and chlorine levels and the amount of nutrients in the

soil. In total the salt level should not exceed 1.5 mS. The chlorine level in particular should not

exceed 50 mg/l. If the salt or chlorine levels are higher, then the soil should be well flooded

beforehand with suitable water. Make sure the soil is flooded thoroughly before cultivation as this will prevent deterioration of the soil structure. When using fresh organic fertilizer ensure salt levels are not too high and do not use large quantities of artificial fertilizer at the same time.

Fertilizer base dressingFertilizer base dressingFertilizer base dressingFertilizer base dressing

To obtain adequate information on the soil’s nutrient status it is essential to take soil samples well before the start of the growing period. Depending on the soil’s structure, nutrient condition and salt level, well decomposed organic compounds, such as 1 m3 well-rotted cow manure per 100 m2, can be worked thoroughly through the soil well before planting. Fresh farmyard manure

usually has excess salt levels. So be careful with fresh manure as it can quickly cause root scorch. On heavier and more humus-rich soils, the use of farmyard manure often has an adverse effect on the structure of the soil because it causes compaction. It is therefore advisable to use

peat compost or similar products. Sand or drift sand (lava sand) are also used occasionally. Lilies do not need a high nutrient level and this is certainly true during the first three weeks of cultivation. Good root development with no salt damage is more important at this stage. It is however advisable to apply phosphate and potash in the form of straight fertilizers on

nutrient deficient soils (see result of soil analysis), as it will not be possible to apply these compounds during cultivation, given that lilies are very susceptible to fluorine which causes leaf scorch, (particularly on soils with a low pH). Fluoride retaining fertilizers such as super and triple

super phosphate and a number of compound fertilizers should not be used. It is much preferable to use fluorine-deficient fertilizers such as dicalcium phosphate. Irrigation waterIrrigation waterIrrigation waterIrrigation water The salt level (EC) of irrigation water contributes to the total salt level of the soil and should therefore also be low: 0.5 mS/cm or lower. With an EC of approx. 0.1, rain water complies with

this level. The EC of spring or surface water, when used extensively or during the summer months, can increase considerably. The maximum acceptable chlorine level of irrigation water used for greenhouse irrigation is 50 mg. Needless to say, carrying out regular checks on salt and chlorine levels should not be considered

a waste of time. If irrigating with water which exceeds these levels the soil should be kept constantly moist to prevent an increase in salt concentrations which can occur if the soil becomes too dry.

4. General culti4. General culti4. General culti4. General cultivation proceduresvation proceduresvation proceduresvation procedures On arrivalOn arrivalOn arrivalOn arrival

Immediately on arrival, bulbs should be planted in moist soil. Bulbs which are not frozen (new crop December-January-February) and defrosted bulbs should be planted on the same or the following day.

Frozen bulbs should be slowly defrosted (do not place in the sun) at a temperature of 10°C to 15°C with the plastic packaging opened up. Defrosting at higher temperatures results in quality loss. Once bulbs have been defrosted they cannot be refrozen because of the risk of frost

damage. If it is not possible to plant non-frozen and defrosted bulbs they can be stored for a maximum of 2 weeks at +0°C to +2°C or for 1 week at +2°C to +5°C with the plastic open. Higher storage temperatures and longer storage periods cause unwanted shoot development and, if bulbs have been badly packed, bulb desiccation, resulting in shorter stems and fewer flower

bulbs. Another important point to remember is that box temperatures can rapidly increase to far above the temperature inside the storage owing to accelerated bulb respiration.

Bulb sizeBulb sizeBulb sizeBulb size It is better to use the smallest recommended bulb size for the various lily groups when conditions

are favorable i.e. during a period with sufficiently low temperatures for plants at the development stage e.g. when planting in December through to March. In light deficient periods a slightly smaller (+wider planting) and during a high temperature period a larger bulb size should be used. Note that there is a greater risk of leaf scorch when using larger bulb sizes of certain cultivars among the Asiatic and Oriental hybrid groups. The choice of bulb size also depends on the required flower quantity. As a general rule, the smaller the bulb the less buds per stem, and the shorter the stem the lighter the plant will be.

The table below shows the range of bulb sizes for each lily group. Bulb size per group

• Asiatic hybrids 9-10 cm, 10-12 cm,12-14 cm, 14-16 cm,16 cm and higher

• Oriental hybrids 12-14 cm, 14-16 cm, 16-18 cm, 18-20, 20-22 cm and 22 cm and higher

• Longiflorum hybrids 10-12 cm, 12-14 cm,14-16 cm, 16 cm and higher

• L/A hybrids 10-12 cm, 12-14 cm,14 cm and higher

Cultivation siteCultivation siteCultivation siteCultivation site Lilies are grown in glass or plastic houses, either direct in the border soil or in boxes. This ensures crops are not affected by unfavorable weather conditions and the environment can be

controlled. Outdoor cultivation of lilies is only possible in regions where the climate remains favorable during the cultivation period. It is necessary for growers to realize the risks involved in outdoor

cultivation, especially strong winds, hail, periods of frost and a high humidity (Botrytis). Outdoor cultivation demands particularly “strong”, moisture-retaining and well-drained soils plus a good irrigation system, and wind and shade screens. These are needed to achieve sufficiently long stems during the summer months. The choice of cultivar (long-stemmed cultivars) is also

vital.

Planting procedures, plant depth and crop mulchPlanting procedures, plant depth and crop mulchPlanting procedures, plant depth and crop mulchPlanting procedures, plant depth and crop mulch

During the first three weeks after planting a lily bulb depends on roots already formed before planting for its uptake of water, oxygen and nutrients. It is therefore important that bulbs have vigorous, disease-free, fleshly roots when planted. When the lily stem starts to grow above the

soil, the so-called stem roots start developing on the underground portion of the stem, directly above the bulb. These roots quickly take over from the bulb roots and supply the plant with 90% of its water and nutrient uptake. To obtain high quality lilies, roots must be allowed to develop

properly. To ensure good root development bear the following six points in mind:

• only plant in disease-free soil

• make sure the soil is sufficiently cool. Take this into account even before planting, by shading, aerating and using cold irrigation water. Cover the soil immediately after planting with suitable compounds such as potting compost, rice chaff, straw etc. to prevent heat penetration, drying out and soil structure deterioration

• in warm weather only plant in the morning or evening

• postpone planting for one or two days in warm weather

• prevent bulbs drying out when planting by only planting a small number of bulbs at a time in the bed or by planting directly from the boxes. Dried out bulb scales or bulb roots will always result in quality loss

• plant bulbs sufficiently deep in a slightly moist soil; with a layer of 6 cm - 8 cm soil in the winter and 8 cm - 10 cm of soil in the summer on the top of the upright bulb. To prevent bulb roots from damage do not plant too firmly.

Planting densityPlanting densityPlanting densityPlanting density Plant growth varies considerably between the groups, cultivars and bulb size planted, all of

which influence the optimum planting density. The planting density is also affected by the season and the soil type. A high planting density is advised in the months of high temperature when light intensity is high. In poor light periods (winter) or under poor light conditions a lower density should be used. On

heavy soils, for example peat, vigorous growth occurs and therefore plants can be spaced wider apart. The table indicates the minimum and maximum planting densities per net m2 for the various bulb sizes of each group.

StakingStakingStakingStaking

Depending on the time of year and the cultivar it may be necessary to stake plants during the growing period. It will always be necessary to stake plants during the winter months and for the remaining months cultivars longer than 80-100 cm will often need staking. If stems are pulled up during harvesting instead of being cut then the remaining stems will definitely need support to

prevent toppling. Chrysanthemum netting is frequently used to support lilies and during the growing period the height of this netting should increase parallel to the growth of the lilies.

NutritionNutritionNutritionNutrition

Nitrogen should be applied to both nutrient-rich and impoverished soils in the ratio of 1 kg of calcium nitrate per 100 m2, three weeks after planting. If plants are weak during the growing period due to nitrogen deficiency, then a top dressing of 1

kg of quick-release nitrogen per 100 m2 can be applied up to three weeks before harvesting. The dressing can be applied either through the irrigation system or by hand between dry plants. To prevent leaf scorch when applying via the irrigation system, wash off the crop well with clean

water after the nitrogen application. Based on pratical experience and test results, target standards for lilies have been developed in order to achieve acceptable crop growth and flowering. Mineral fertilizers may be scattered between the crop by hand. However, to minimize leaf scorch

it is better to distribute the fertilizer by means of an irrigation system. Liquid fertilizer may be made up from water-soluble nutrients without residue agents. The second table shows the standard nutrient solutions suitable for lilies. To prevent leaf scorch, rinse with clean water after

applying the nutrient solution. WateringWateringWateringWatering

Moisten the soil a few days before planting to enable rooting to start straight after planting. Water copiously several times directly after planting to prevent the soil collapsing or deteriorating and to allow the bulbs and the bulb roots to be in close contact with the soil. Check!

Because the stem roots develop in the top layer it must be kept constantly moist. However too much moisture should be avoided as this will have a detrimental effect on the oxygen supply to the roots which in turn will adversely affect the root function. The amount of water depends on the type of soil, the greenhouse climate, the cultivar, the development of the crop and the salt level of the soil. During dry periods, water consumption could increase to 8 to 9 litres per m2 daily. A good way to check the correct moisture level of the soil is to squeeze some soil in your hand. An indication of the correct moisture level is if it is almost impossible to squeeze moisture

from the soil at the same time the soil stays “balled”. Regularly check the irrigation system’s water distribution. The best time for watering is early in the morning so that the crop will be dry by the evening. If necessary turn up the heating or ventilate to prevent Botrytis disease.

Weed controlWeed controlWeed controlWeed control

Do not use herbicides for weed control unless this is absolutely necessary. Far better to remove all weeds or to sterilize the soil before planting by steaming or inundating it. The use of herbicides always involves a risk of damage. After the emergence of shoots but before the foliage opens up significantly, small weeds can be

controlled, in the greenhouse or in the field, by spraying with a suitable herbicide. If much annual meadow grass is present which is not controlled by one herbicide, a combination of herbicides should be used.

Always spray towards the evening on a dry crop using 5 litres of water per 100 m2. The following morning, rinse off the crop thoroughly by means of irrigation. Because of the persistence of herbicides, keep the following points in mind: limit spraying frequency to no more than twice a year on the same site, always apply site by site, and check for damage in succeeding crops.

Further information on the use of herbicides is available from your local information office.

Crop controlCrop controlCrop controlCrop control

It is essential to regularly check the crop and at the same time the soil. The points to pay attention to are:

• soil: dry areas, EC, structure, weed growth, temperature

• crop: stage of growth, color, aphids, thrips

• Botrytis, Pythium greenhouse: climate, plant support.

5. Greenhouse environment5. Greenhouse environment5. Greenhouse environment5. Greenhouse environment Temperature: IntroductionTemperature: IntroductionTemperature: IntroductionTemperature: Introduction

A good root system is of paramount importance in achieving a high quality product as far as lily cultivation is concerned. With this in mind, the optimum recommendation would be for a low, initial (rooting) temperature of between 12°C to 13°C for the first third of the growing cycle or at

least until the stem roots have developed. Lower initial temperatures will extend the growing period unnecessarily and temperatures higher than 15°C will result in a poorer quality product. Soil cooling could be indispensable during the warmer months. Cooling should be reduced very

gradually after 1/3 of the growing cycle is over. Temperature: Asiatic hybridsTemperature: Asiatic hybridsTemperature: Asiatic hybridsTemperature: Asiatic hybrids

To obtain the best quality, a daily temperature of 14°C to 15°C should be maintained for the remainder of the growing period. During the day, the sun may cause the temperature to rise to 20°C, possibly to 25°C, and the temperature at night may drop to between 8°C to 10°C (make

sure the environment is not too moist), which is acceptable. This is one way to save energy during the spring and autumn, provided the crop quality and the speed of growth remain constant. To obtain longer stems or to prevent bud drop it is sensible to lower the temperature from 14°C/15°C by 1°C to 1.5°C if cultivars are too short or if production is in poor light periods.

Temperature: Oriental hybridsTemperature: Oriental hybridsTemperature: Oriental hybridsTemperature: Oriental hybrids After the rooting period, the optimum daily greenhouse temperature is between 15°C to 17°C. It should be noted that only increases in temperature are acceptable to 20°C-22°C, possibly to 25°C. Temperatures below 15°C can result in bud drop and yellowing of foliage.

Temperature: Longiflorum hybridsTemperature: Longiflorum hybridsTemperature: Longiflorum hybridsTemperature: Longiflorum hybrids The best greenhouse temperature for these lilies after rooting is a temperature of 14°C to 16°C.

The sun may also increase the temperature for these lilies and a temperature of 20°C to 22°C is acceptable. Under poor light conditions, the greenhouse temperature may be reduced by 1°C to 1.5°C. A minimum day and night temperature of 14°C must be maintained to prevent discoloring and

splitting of the flower petals. Temperature: General informationTemperature: General informationTemperature: General informationTemperature: General information

During late autumn, winter and early spring it is not normally difficult to maintain the above-mentioned greenhouse temperatures. However the opposite is true for the summer months. Even before planting but also during cultivation it will be necessary to ventilate, screen and use cold

water to maintain the recommended temperatures. High temperatures produce reduced stem length and fewer buds per stem.

Relative humidityRelative humidityRelative humidityRelative humidity

A suitable relative humidity level is between 80% to 85%. It is important to avoid large fluctuations in levels and any changes should occur gradually. Rapid changes cause stress which could result in leaf scorch in susceptible cultivars. Use screening, prompt ventilation and

watering to prevent these problems. It is not advisable to suddenly ventilate during the day on very warm days or very cold days (freezing open weather) when the relative humidity of the outdoor air is very low; it is better to

ventilate early in the morning when the relative humidity outdoors is higher. Watering copiously during the day with a low relative humidity level inside the greenhouse is not the right thing to do either. Watering early in the morning is the best time to water in these conditions. In mild, poor light, calm or damp weather conditions, relative humidity is often very high and

measures will have to be taken to decrease the r.h. by heating and ventilating simultaneously. VentilationVentilationVentilationVentilation

Ventilating is an extremely important factor when considering temperature control and decreasing air humidity levels. An important point to remember here is that air humidity levels inside the greenhouse must not drop too quickly as a rapid withdrawal of moisture can result in

leaf scorch and quality loss. ScreeningScreeningScreeningScreening

The use of screens can affect temperature levels, air humidity levels and light conditions inside the greenhouse. During months of high light intensity, temperatures inside the greenhouse can rise dramatically in spite of ventilation. In conditions like this it will be necessary to screen to prevent a poor quality crop. For further information see Lighting equipment and Screening equipment. During summer months in countries with a high light intensity, growers can reduce light level by

50% for Asiatic and Longiflorum hybrids and 70% for Oriental hybrids. CO2CO2CO2CO2

CO2 has a positive effect on the growth and flowering of lilies. Try to achieve a concentration of 800 to 1000 ppm. A higher concentration (± 2000 ppm) is needed for the Longiflorum hybrids as this group uses high levels of CO2.

6. Other cultivation systems6. Other cultivation systems6. Other cultivation systems6. Other cultivation systems The benefits of box cultivationThe benefits of box cultivationThe benefits of box cultivationThe benefits of box cultivation

The cultivation of lilies in boxes is increasing both in the Netherlands and elsewhere. The reasons for this are:

• a specific rooting room for cultivation means:

o improved crop quality because of the low and controlled starting temperature resulting for example in longer plants (the possibility of summer cultivation of Star Gazer and other varieties)

o a shorter greenhouse period, which means more efficient use of the greenhouse, plus the benefit of energy-saving during the winter months

o distribution of labour o more opportunities for crop scheduling

o disease control due to the use of fresh rooting media e.g. potting compost, with the right structure (good drainage/aeration)

• a large improvement in the crop. This is particularly so with the Oriental hybrids

• the possibility of linking cultivation methods to an environmentally friendly cultivation system

Besides the benefits mentioned above there are also a number of disadvantages such as the high labour usage and the additional capital needed for box cultivation.

Box cultivation: Rooting mediumBox cultivation: Rooting mediumBox cultivation: Rooting mediumBox cultivation: Rooting medium

The substrate recommended for box cultivation should be a good moisture-retentive and light medium. A popular substrate is potting compost; a mixture of different types of peat plus some perlite (fluorine free!) or sterilized rice chaff or garden soil or coarse-grained sand if possible. Good and frequently used mixed peats for lilies include a 40% to 80% peat mixture of black peat

well frozen for a year plus 60% to 20% peat litter (white peat). The pH should be increased to 6 to 7. The rule of thumb for increasing the pH by a factor of 0.4 is to add 1 kg of calcium carbonate retaining lime per m3.

As a base fertilizer, 0.5 kg 12-14-24 including trace elements per m3, should be added to potting compost mixtures. If the potting compost is to be recycled for use for a number of successive crops then it should first be sterilized before re-use. This can be done by steaming or with a fungicide. Prolonged use of recycled compost leads to a loss of quality as a result of structure

and disease problems and it is therefore not recommended. The potting compost should be reasonably moist when crops are planted.

Box cultivation: Planting methodBox cultivation: Planting methodBox cultivation: Planting methodBox cultivation: Planting method Lily/tulip storage containers are usually used as boxes. They should have a minimum inside depth of approx. 12 to 14 cm. Bulbs are planted with at least 1 cm of soil under the bulb and 8 cm

of soil on top of the bulb. The criteria that applies here is that the deeper the layer the bigger the water buffer. The depth of the compost under the bulb is not that important and its main function is to support bulbs during planting to ensure a good surface distribution of bulbs. The plant

density corresponds to the density of bulbs planted in border soil in the greenhouse.

Box cultivation: Rooting roomBox cultivation: Rooting roomBox cultivation: Rooting roomBox cultivation: Rooting room

Boxes can be placed in the greenhouse directly after planting or they can be put into cold storage (the rooting room) for periods ranging from one to a number of weeks. Because of shoot development it is better to stack boxes in a criss-cross fashion rather than place them vertically

on top of one another. Development and growth of the bulb and stem roots can then take place under ideal conditions. If boxes are brought into the greenhouse every week, it is possible that during periods of warm weather crops from boxes brought into the greenhouse at different times

will start to flower simultaneously. This can be prevented by maintaining a rooting temperature of 10°C. The temperature in the rooting room can vary from -0.5°C, which completely inhibits development, to 12°C to 13°C. The latter temperature is the optimum temperature for rapid root

development. Boxes can then be placed in the greenhouse approx. 3 to 4 weeks after planting. The visible part of the shoot should not be longer than 8 cm to 10 cm at this stage.

Box cultivation: Cultivation proceduresBox cultivation: Cultivation proceduresBox cultivation: Cultivation proceduresBox cultivation: Cultivation procedures After the boxes have been placed in the greenhouse, extra attention will have to be given to watering. The soil in the boxes does tend to dry out quickly and therefore needs to be watered

more regularly. The soil should be kept constantly slightly moist. Drip irrigation systems, such as an “an online system”, will be a useful asset here. As far as other cultivation procedures are concerned, they are similar to those which apply to

direct planting in the greenhouse. Outdoor cultivation: IntroductionOutdoor cultivation: IntroductionOutdoor cultivation: IntroductionOutdoor cultivation: Introduction Lilies can also be planted outdoors for a one-year or multi-year growing period. However results depend a great deal on weather conditions, the soil type (heavier soils produce shorter plants) and the cultivar in question. Choosing whether to keep lilies long-term depends on the type of

soil (lighter soils results in very limited bulb growth) plus bulb prices. Should the crop quality of cheaper cultivars decline it may be better financially to replace old bulbs with new ones every year. The choice of cultivar depends on the soil type (heavier soil = shorter plants and therefore taller

cultivars should be used), the Botrytis susceptibility of cultivars and if shading is to be used during cultivation. Shading produces taller plants. Short cultivars are not suitable for outdoor cultivation.

Outdoor cultivation: Planting timeOutdoor cultivation: Planting timeOutdoor cultivation: Planting timeOutdoor cultivation: Planting time The best time to plant is from spring onwards when there is less chance of heavy night frosts. The

latest time to plant depends on the regional climate during the growing period. For example, harvesting should be completed before the average 24-hour temperature has dropped to below 11°C in the case of Asiatic and Longiflorum hybrids and to 13°C in the case of Oriental hybrids.

Experience has shown that it is better to plant bulbs intended for long-term crops in the spring as this means enhanced crop quality in the second year. Planting in late autumn can only be done if bulbs do not run the risk of frost damage during the winter and are not troubled by night frosts once they start to emerge in spring. In dry soils, even a

light night frost (-1°C and lower) can cause damage to emerged lilies. Therefore keep the soil moist and water lilies during the night frost period. Damage will however occur if temperatures drop to below -5°C in spite off watering.

Outdoor cOutdoor cOutdoor cOutdoor cultivation: Planting methodultivation: Planting methodultivation: Planting methodultivation: Planting method

It is preferable to use the larger bulb sizes (taller plants) provided the cultivar is not susceptible to leaf scorch. This also applies to long-term crop cultivation as this ensures good stem quality in subsequent years. If bulbs are planted during warm weather, there will be a greater chance of

bulbs producing double noses the following year. This depends on the cultivar and bulb size, as bigger bulbs are more likely to produce double noses. Outdoors bulbs are planted with 10 to 15 cm of soil on top of the bulbs. Plant density depends on the number of years the crop will be

grown. For one-year cultivation, plant density should be 10% higher and with long-term cultivation the density should be 15% to 20% lower as indicated for greenhouse cultivation per cultivar, bulb size and time of year.

Outdoor cultivation: Other cultivation proceduresOutdoor cultivation: Other cultivation proceduresOutdoor cultivation: Other cultivation proceduresOutdoor cultivation: Other cultivation procedures Nutrition is similar to that for greenhouse cultivation. If artificial fertilizers cannot be applied

through the irrigation system during cultivation, an increased quantity of base dressing or a slow-release fertilizer will have to be applied provided salt levels in the soil will allow it. If possible, crops should be shaded during cultivation to improve crop length and crop quality. Particular attention will have to be paid to the control of Botrytis, aphids and virus diseases

during cultivation. For long-term cultivation, a healthy cultivar and also the demand for a particular cultivar will be vital factors in determining profits. If neither of these factors are present cultivation should be

discontinued. Pot lilies: IntroductionPot lilies: IntroductionPot lilies: IntroductionPot lilies: Introduction Besides production for the cut flower trade, the cultivation of pot lilies for use indoors, on the patio or the garden can also be an extremely viable option. Up until recently shorter cut lilies were used for this. By using chemical growth regulators such as paclobutrazol (Bonzi) and

ancymidol (Reducymol), applied by watering onto the pot, spraying the foliage or by immersing bulbs, lilies were kept short with an optimum stem length of 30 cm to 40 cm. However, results were extremely variable depending on a large number of factors such as the growing period, the substrate used, the cultivation temperature and the cultivar qualities. Nowadays there are a large

number of genetically short lilies (see table) in a wide variety of colors available for continious cultivation and growth regulators no longer need to be used. Pot cultivation is very similar to cut flower cultivation. The specific cultivation procedures are as follows:

Pot lilies: Planting methodPot lilies: Planting methodPot lilies: Planting methodPot lilies: Planting method A number of bulb sizes can be used for pot lilies; the most suitable are listed in the table,

although this always depends on the total foliage volume of the cultivar. Furthermore the table compares the various lily groups and the number of bulbs needed per pot. The bulb size chosen must meet the required minimum number of buds per pot, also listed in the table. The table also

indicates the bulb sizes required per pot for planting 1,3 or 5 bulbs per pot. Larger bulb sizes should be chosen for the following: double nosed bulbs, bulbs planted in summer, Longiflorum hybrids planted in the autumn and bulbs to be grown with the aid of

assimilation lamps. The best choice of substrate to use in pots is a disease-free, moisture retentive, light medium with a pH between 6 and 7. Potting compost (see Box cultivation, sub-heading: Substrate)

supplemented by 30% drift sand or perlite (fluorine free) is very suitable for use in pots. Add a base dressing of 1 to 1.5 kg Osmocote 14-14-14 and 1 to 2 kg sulphate of potash-magnesia per

m3. Bulbs should be planted at the bottom of the pot on a 1 cm layer of potting compost and, if 2

or more bulbs are planted per pot, the bulb noses should face the out sided of the pot. Top up with potting soil. After planting, ensure that the substrate is thoroughly moist. Pot lilies: Cultivation proceduresPot lilies: Cultivation proceduresPot lilies: Cultivation proceduresPot lilies: Cultivation procedures

Keep the substrate in the pot reasonably moist. There is a chance of yellow foliage occurring during the growing period. This can be caused by the habit of the cultivar, poor light conditions

(too many pots per m2), a crop which is grown under too moist conditions or Pythium attack. For the optimum greenhouse climate you are referred to the relevant chapter for cut flower lilies. Research has shown that by maintaining an increased night-time temperature, compared to the daytime temperature, a shorter stem can be achieved. This method is known as the Dif-method. If

possible, the daytime temperature can be lowered compared to the nighttime temperature. Reducing the day-time temperature during the first two hours after sunrise compared to the same reduction in temperature during the rest of the day has an enormous effect on the development

of the stem length (reduced stem length). When applying this technique, you should realise that for a plant the day begins at sunrise and ends at sunset but the effects of changing weather conditions should also be considered.

Pot lilies: Harvesting and post harvest treatmentPot lilies: Harvesting and post harvest treatmentPot lilies: Harvesting and post harvest treatmentPot lilies: Harvesting and post harvest treatment Pot lilies are marketed when the lower buds show sufficient color. The distribution chain should

be kept as short as possible to prevent bud drop as a result of poor light. It is unacceptable to dispatch lilies at an earlier stage of development due to increased susceptibility to lack of light. To guarantee good appearance of the pot lilies, it is important to make sure pots are clean before are dispatch and that sufficient water has been given. If necessary any yellow leaves should be removed. Provide pots with a label displaying a product photograph plus tips for consumers and ensure that pot lilies are attractively sleeved. Avoid storing pot lilies in a cold store; if lilies must be placed in cold store ensure the duration is

as short as possible. The minimum temperature should be +5°C, both in the cold store and during transportation. It is possible to store Asiatic hybrids at a temperature of +3°C. Although these temperatures do not stop flower development, lower temperatures can cause insufficient opening of the flower buds once bought by consumers.

7. Harvesting and post harvest treatment7. Harvesting and post harvest treatment7. Harvesting and post harvest treatment7. Harvesting and post harvest treatment Flowering and harvestingFlowering and harvestingFlowering and harvestingFlowering and harvesting

For good results for the final customer i.e. “the consumer” it is vitally important to harvest lilies when they are sufficiently developed but not over-mature. Before harvesting stems with ten or more buds must be at a stage when at least three buds show

color, stems with five to ten buds must have at least two in color and stems with less than five buds must have at least one bud in color. Harvesting at an earlier stage results in miserable, pale flowers with some buds that fail to open. Over-mature harvesting i.e. when several buds have

already opened can result in post harvest and distribution problems, including spotting by pollen, bruising of the petals and opened flowers as a result of ethylene emissions produced by already opened flowers. If necessary cut off any open flowers. During harvesting, it is better to cut stems rather than to pull them. Pulling causes a lot of root

disturbance to the remaining plants and if wire support netting has not been used plants can even topple. In fact stems of Oriental and Longiflorum hybrids cannot be pulled because of their strong root development. It is preferable to harvest lilies in the morning to limit desiccation and

for the same reason also to limit the dry storage period in the greenhouse to a maximum of 30 minutes. Grading and bunchingGrading and bunchingGrading and bunchingGrading and bunching

After harvesting, stems are graded according to the number of flower buds per stem, length and firmness of stems and any possible foliage and flower bud abnormalities. The lily stems are then bunched and during this process 10 cm of foliage is removed from the bottom of the stem. This is done manually or with a special defoliating machine. Defoliating enhances presentation and also increases the vase-life of lilies as less water pollution will occur. Any yellow or damaged foliage is also removed. After bunching, stems are cut if lilies are to be placed in water. The final stage,

wrapping, is then carried out. The wrap used for lilies should protect both the flower buds and the foliage. The grading and bunching processes can be carried out mechanically by using a so-called flower bunching line.

This results in a drastic reduction in the handling phase (harvesting - placing in water), which, to prevent drying out, should only last for a maximum of 1 hour. In addition this improves the physical comfort of staff while working at the flower bunching line. If it is not possible to grade and bunch lilies immediately after harvesting then the best thing to

do is to place them in cold storage in clean water immediately. For Asiatic hybrids, a pre-treatment agent can be added to the water.

StorageStorageStorageStorage After bunching, lilies need to be placed directly in water in the cold storage room. Add pre-treatment agents of silver thiosulfate + GA3 (e.g. 6 ml Chrysal A.V.V. + one S.V.B. tablet per 3

litres of water) to the water of Asiatic hybrids. The pre-treatment agent silver thiosulfate can be harmful when used for other lily groups. If the weather is warm it is advisable to use pre-cooled water as flowers will not mature so

quickly. At 2°C to 3°C the minimum and maximum treatment period of flower conditions is 4 and 48 hours respectively. If it is not possible to continue treatment for 4 hours, then maintain a treatment period of at least 2 hours in the processing room as this will improve the keeping quality of lilies during the distribution stage as they will then be less susceptible to ethylene. The

solution can only be used for a maximum of one week until it becomes cloudy.

When lilies have absorbed sufficient quantities of water they can be stored dry in the cold store

room, although it is better to continue storage in clean water. The optimum storage temperature of cut lilies is 2°C to 3°C and storage time should be kept as short as possible. It is a well-known fact that the Oriental hybrid “Star Gazer” will show brown spots on the outside of the petals if harvested at a greenhouse temperature of 30°C or higher and

subsequently stored at 2°C to 3°C. In these conditions it is advisable to store at a temperature of at least 4°C.

DispatchDispatchDispatchDispatch Before dispatch, lilies are packed into perforated boxes to prevent high concentrations of ethylene produced by the open flowers.

The ethylene gas causes rapid maturity which shows as miserable flowers, bud drop and reduced keeping quality. During packaging make sure the stems are put into the box in a dry state as this will prevent over

heating and development of fungi. It is essential that lilies are transported at low temperatures, preferably in refrigerated vehicles (+2°C to +3°C) as this will prevent flower bud development and also the harmful effects of ethylene. During long-haul transportation, it is certainly advisable to pre-cool the boxes before they are dispatched.

On arrival at the wholesaler’s or retailer’s, after stems have been cut again, lilies should be placed in clean water at a storage temperature of 1°C to 5°C.

8. Planning and labour8. Planning and labour8. Planning and labour8. Planning and labour PlanningPlanningPlanningPlanning

It is vital to plan in advance to achieve optimum scheduling, production and commercial results and it is of paramount importance to carry out a thorough study of the sales potential and price expectation beforehand. A general assumption is that a regular supply of flowers in various

colors creates a favorable market. Even so, during times of increased market demand for flowers, customers will still expect products to be available. This is why good planning is vital. It is also crucial to determine the correct delivery date of bulbs and to ensure that the greenhouse is not

unnecessarily empty; furthermore planning ensures an even distribution of labour. An essential aspect of sound planning is to draw up planting schedules 1 to 2 years in advance. Early planning also gives the grower time to order limited supplies of certain cultivars on time. Data is necessary to prepare plant schedules and information gathered from your own business will certainly be

useful for this. The so-called registration system is a way for you to compile the information you will need for worthwhile planning (company management). Important information needed for planning:

• the net greenhouse floor area available or, for outdoor cultivation, the net ground area

available

• the cultivar, with relevant information on its growing period and qualities plus information on its suitability for year-round cultivation and its availability

• storage period for bulbs; newly harvested bulbs are slower (±2 weeks) and tend to

emerge more irregularly than bulbs from the previous year

• the right time to apply general soil sterilization if necessary

• cultivation temperatures required

• planting density

• planting date

• date of complete harvest

• time required to prepare soil for planting

• labour required and labour available

• assessment of the financial yield

Labour requirementsLabour requirementsLabour requirementsLabour requirements To compile a planning schedule, it is extremely important to have details on the labour

requirements during cultivation, particularly details on all the specific activities involved. Activities during and immediately after harvesting accounts for about 50% to 60% of the labour requirements. Therefore it is essential to spread harvesting to prevent large labour peaks. A flower bunching line does show a saving of ± 15% on labour requirements during harvesting

and post harvest treatment.

9. Crop protection and disease control9. Crop protection and disease control9. Crop protection and disease control9. Crop protection and disease control GeneGeneGeneGeneral soil treatment: Introductionral soil treatment: Introductionral soil treatment: Introductionral soil treatment: Introduction

Since the soil must be free of pathogens, cultivation must take place under optimum conditions. If the soil needs treatment, this can best be done by use of annual soil sterilization. Steaming or use of a chemical soil sterilant are both possible methods of disinfection. The effect of steaming

and chemical soil disinfection is determined by temperature, time and concentration. General soil treatment: SteamingGeneral soil treatment: SteamingGeneral soil treatment: SteamingGeneral soil treatment: Steaming

When steaming at a soil depth of 25 cm to 30 cm, a temperature of between 70°C and 80°C should be maintained for at least 1 hour. Steaming with low pressure gives better results than at high pressure. Nearly all soil problems

can be controlled using this method except for the Pythium fungus, which is usually not adequately controlled. This means that a supplementary chemical treatment is nearly always necessary. On silt-retaining soils with a low pH, steaming can lead to excess of manganese.

Steaming for a short period in a light and dry soil where the pH level has been raised by a lime application beforehand will help restrict this excess of manganese. General soil treatment: Chemical treatmentGeneral soil treatment: Chemical treatmentGeneral soil treatment: Chemical treatmentGeneral soil treatment: Chemical treatment

A chemical sterilant is most effective at soil temperatures of at least 10-12°C, while the soil is covered with plastic film. After 7-10 days (in summer 3 days will suffice), the plastic can be removed. For more information concerning the sterilants to be used and the application method, we refer you to your local information service. Additional soil treatmentAdditional soil treatmentAdditional soil treatmentAdditional soil treatment

Due to the rapid regrowth of Pythium fungus, a general soil treatment applied once a year is not enough. To control this fungus, the soil need additional treatment using a fungicide applied

immediately before every planting or crop. All fungicides used should be mixed evenly through the top soil to a depth of 10-15 cm. To obtain good distribution, fungicides in powdered form are mixed with sand and then applied by hand or mixed with lukewarm water, sprayed through a wide angled spray nozzle and then worked in

thoroughly with a rotary cultivator. With soils susceptible to structural damage, working the fungicides initially through the soil manually and then lightly working them into the soil with a rotary cultivator is recommended. For information concerning the recommended fungicides and

how much to apply, we refer you to your local information service. Potting compost can also be infected with the Pythium fungus. It is unusual for fresh potting compost to be infected but in recycled potting compost there is a very definite risk of infection. Therefore the compost should be treated beforehand with an effective soil applied fungicide

against Pythium. If necessary, an effective fungicide can be watered into the crop during cultivation (see root rot).

Bulb treatmentBulb treatmentBulb treatmentBulb treatment Bulb disinfection just before planting is not carried out by lily growers as bulbs will have already been disinfected by suppliers before packing. Bulb disinfection will therefore not be discussed

here.

Diseases caused by fungi: PenicilliumDiseases caused by fungi: PenicilliumDiseases caused by fungi: PenicilliumDiseases caused by fungi: Penicillium During storage, diseased areas, covered first with a white, and later on with a fluffy, bluish-green fungus, are visible on the scales. After the initial infection and during the entire storage period

the rot will gradually increase, even when temperatures are low (-2°C). The infection can eventually penetrate the basal plate making bulbs worthless or affecting bulbs so that they produce extremely retarded plants.

Although infected bulbs do not always look very healthy, plant growth will not be affected as long as the basal plate remains intact. After planting, the infection is not transmitted to the stem and rarely infects plants from the soil.

Cause The infection is caused by the Penicillium fungus and is transmitted during storage when the fungus penetrates tissue via wounds.

Control

• Prevent desiccation of the bulb during storage and store at the lowest recommended temperature

• Do not plant bulbs which have an infected basal plate

• Plant infected batches as quickly as possible, preferably in the period from December to March (slow start)

• Before and after planting, maintain a suitably moist soil.

Diseases caused by fungi: Bulb and scale rot and FDiseases caused by fungi: Bulb and scale rot and FDiseases caused by fungi: Bulb and scale rot and FDiseases caused by fungi: Bulb and scale rot and F Plants infected with bulb and scale rot will remain retarded in growth. The foliage of these plants is pale green in color. Underground, brown spots will appear on the top and sides of the bulb scales or at the junction of the bulb scales with the basal plate. These spots will eventually start to rot (scale rot). If the basal plate and the scales are infected at the base then the bulb develop bulb rot. Fusarium stem disease is an above-ground infection recogni-zable by the premature

yellowing of the lower leaves, which turns brown and drops. On the underground part of the stem, orange to dark brown spots appear which later become enlarged and spread to the internal part of the stem. Rotting occurs and plants finally die prematurely.

Cause Bulb and scale rot as well as Fusarium stem disease are caused by both Fusarium oxysporum and Cylindrocarpon destructans. These fungi infect the underground parts of the plants where

wounds occur as a result of splitting bulb and stem roots or by a parasite infestation. The fungi can be transmitted on the bulb but the plants can also become infected from the soil. Certain cultivars are particularly susceptible to infection.

Control

• Treat the infected soil or suspect soil by applying a general soil fungicide (see General soil treatment)

• Batches which are slightly or moderately infected should be planted as soon as possible

at low soil temperatures. It is preferable to only plant these bulbs in the period from December to March

• Maintain the lowest possible soil and greenhouse temperatures during summer

cultivation.

Diseases caused by fungi: RhizoctoniaDiseases caused by fungi: RhizoctoniaDiseases caused by fungi: RhizoctoniaDiseases caused by fungi: Rhizoctonia

If the infection is slight, damage will be restric-ted to the lower green leaves of the young shoot. Sunken light brown spots appear on the leaves. In general, the plant will continue to grow although it will be a little retarded. The growth of badly infected plants will be checked above

ground, and the white, underground foliage and the first leaves above the ground will be rotten or will wilt and drop, leaving a brown scar on the stem. The younger leaves and the growing point are usually damaged. Plants infected as badly as this will have poor stem root development,

which in turn will result in retarded growth and unsatisfactory flowering or no flowers at all, as flower buds will have desiccated at an early stage. Cause

The disease is caused by the fungus Rhizoctonia solani. The fungus mainly attacks the plant from the soil and is most active in moist conditions at temperatures above 15°C. The same fungus can affect a large number of other plants such as tulips, irises, chrysanthemums and tomatoes so

that many soils can be infected with this fungus. Control

• Disinfect infected or suspect soil using a general soil fungicide (see General soil

treatment). After disinfection it will be essential to ensure the soil is not re-infected, particularly during the summer months when soil temperatures are high. Hygiene is a particularly important factor and if necessary the use of a supplementary soil fungicide (see below) may need to be considered.

• If it is not possible to apply a general soil fungicide and previous crops have shown that infection is likely, then pre-treat the soil with a suitable Rhizoctonia control fungicide (incorporate thoroughly to a depth of 10 cm) before plan-ting

• Summer crops (soil temperature above 16°C) always require soil treatment

• Ensure rapid shoot development: provide the soil with sufficient moisture; plant bulbs with good root systems

• During the summer maintain the lowest possible soil temperature.

Diseases caused by fungi: PhytophthoraDiseases caused by fungi: PhytophthoraDiseases caused by fungi: PhytophthoraDiseases caused by fungi: Phytophthora Plants with foot rot (Phytophthora) are retarded in growth or wilt suddenly. The stem base is infected with soft rot and is dark green to dark brown in color, spreading upwards. The leaves

become yellow, and start to discolor at the base of the stem. A similar soft rot infection often occurs in the part of the stem above the ground causing the stem to topple or bend.

Cause This disease is primarily caused by the fungus Phythopthora nicotianae but can also be caused by Phytophthora parasitica. Phythophthora is unknown in the Dutch bulb growing industry;

however in sub-tropical climates it can affect a wide variety of plants and consequently can be found in most cultivated soils. The disease is prevalent in soils after the cultivation of tomatoes and gerbera and can remain in moist soils for a number of years. Soils which are too moist and

have high temperatures (above 20°C) will encourage this disease. Control

• Give infected soil a general soil treatment (see General Soil Treatment).

• A supplementary soil treatment or an application during cultivation with the fungicide used for Pythium control is also an effective method of controlling foot rot

• Ensure that the soil is well drained

• Prevent the crop from remaining wet for long periods after watering

• Maintain the lowest possible soil temperature during the summer months.

Diseases caused by fungi: PythiumDiseases caused by fungi: PythiumDiseases caused by fungi: PythiumDiseases caused by fungi: Pythium

This fungus affects either single plants or plants within a limited area. Plants remain short, the lower foliage turns yellow and the upper foliage becomes narrower, of a paler color and usually wilts especially under conditions of high transpiration. There is a greater amount of flower bud desiccation in plants affected by root rot and these plants are affected by bud drop during the

winter months. In all cases the flowers are smaller and they often do not fully open or they do not color teadily. When lifted, either transparent, light brown, rotting areas are visible on the bulb and stem roots or they are completely limp and watery.

Cause This form of root rot is caused by Pythium fungi, with Pythium ultimum the most frequently occuring fungus. These fungi generally thrive in moist conditions and at temperatures of 20°C -

30°C. The fungus remains both in the soil and in the bulb roots. Unsatisfactory cultivation conditions, such as bad soil structure and soils with high salt content or soils which are too moist stimulate this root disease. Control

• Give infected or suspected soil a general soil treatment (see General Soil Treatment)

• Give an additional soil treatment immediately before planting (see additional soil treatment)

• Maintain a low soil temperature during the initial cultivation phase and follow the correct cultivation procedures throughout the entire growing period

• Cultivation in boxes containing potting compost plus peat will keep pythium in check. The same result can be obtained by working potting compost into the greenhouse soil

• After the crop has emerged or if Pythium infection is likely, a fungicide effective against Pythium which can easily be watered onto the crop can be used, preferably in the evening. Water for a few minutes (approx. 3 min.) before and after the fungicide has been applied will greatly increase the fungicide’s effect, while washing the crop clean at the same time

• If an infection has been noted, it is advisable to restrict evaporation by the crop by maintaining the coolest possible greenhouse and soil temperatures. This can be achieved by mainly ventilating and screening. The soil should always be kept slightly

moist. Diseases caused by fungi: BotrytisDiseases caused by fungi: BotrytisDiseases caused by fungi: BotrytisDiseases caused by fungi: Botrytis

Small, dark brown dots with a diameter of between 1 mm - 2 mm are visible on the foliage. In moist conditions they can quickly develop into larger, round or oval, sharply defined spots, which are visible on both sides of the leaf. The infected tissue gradually dies off (it becomes withered

and papery). The infection can start in the middle of the leaf blade but also at the edge causing a deformed and growth-retarded leaf to develop. Stems can also be affected and should the infection spread, the leaves generally die off at the

infection site. Flower buds can also become infected, resulting in buds rotting completely or in deformed development. During the first, initial stages of infection, raised areas appear on the outer petals of infected buds. Opened flowers are particularly susceptible to infection which is characterized by the

appearance of grey, watery, round spots known as “fire” spots.

Cause

“Fire” is mainly caused by Botrytis elliptica. In moist conditions, Botrytis elliptica develops spores which are rapidly spread by wind and rain to neighbouring plants. Spores do not germinate on dry plants, which do not therefore become infected.

Control

• Keep the crop dry by adopting the following practices: a. space the crops more widely in wet seasons b. control weed growth

c. water in the mornings, ventilate and heat a little at the same time. Ensure that the crop dries quickly.

• When an infection is suspected (in wet periods), spray frequently with alternating Botrytis

fungicides in the early stages.

• Spray with a fungus-controlling fungicide before flowering, but make sure it does not leave any visible residues or depost.

• Carefully remove all plant remains after cropping.

Damage by pests: AphidsDamage by pests: AphidsDamage by pests: AphidsDamage by pests: Aphids The lower leaves develop normally in infested plants. The upper leaves curl at an early stage of

development and are deformed. The aphids only live on young leaves, particularly on the underside. The yound buds can also become damaged, resulting in the appearance of green spots and flowers can be partially deformed.

Cause The infestation is caused by aphids sucking cell sap. Various aphids can be found on lilies including Neomyzus circumflexus. Control

• Control weeds which often act as host for aphids.

• Spray crops weekly with an insecticide if the presence of aphids has been established, alternating products to prevent resistance.

• If necessary, fumigate the crop shortly before harvest as this will prevent unslightly residues on the flower buds. A greenhouse temperature above 14°C for the first 5 hours is needed for this. Crops should be dry

• To avoid aphids becoming resistant, alternate insecticides.

Abnormalities: Leaf scorchAbnormalities: Leaf scorchAbnormalities: Leaf scorchAbnormalities: Leaf scorch

Leaf scorch occurs at a time when flower buds are not yet visible. First of all, the young leaves curl slightly inward and then a few days later greenish-yellow to whitish spots appear on the scorched leaves. If the leaf scorch is mild, plants will continue to grow normally but if plants are badly scorched

the white spots can turn brown in places and the leaf will bend where the damage has occured. In very severe cases all leaves plus the tender young buds will be lost. Plants will then fail to develop futher. This is known as ‘top scorching’.

Cause Leaf scorch occurs when there is a disturbance in the balance between the absorption and evaporation of water. This is a result of inadequate absorption or evaporation which causes a

calcium deficiency in the cells of the youngest leaves. Cells are destroyed and die. An abrupt change in the relative humidity inside the greenhouse can substantially affect this process as

does a poor root system. High salt levels in the soil and plant growth which is too rapid compared

to the size of the root system are also factors. Susceptibility varies greatly with cultivar (see Selection) and bulb size. Large bulbs are more susceptible than smaller ones. Control

• Diseases and pests which could damage the roots should be effectively controlled

• Soil should be moistened before planting

• It is better not to use susceptible cultivars but if this cannot be avoided do not use larger bulbs as these are extra sensitive

• Plant bulbs with a good root system

• Plant to an adequate depth, i.e. allow 6 cm - 10 cm of soil on top of the bulb

• Prevent large differences in greenhouse temperatures and air humidity levels during periods of increased susceptibility. Try to maintain an R.H. level of approx. 75%.

• Rapid growth must be prevented. Therefore for susceptible Asiatic hybrids maintain a

greenhouse temperature of 10°C-12°C for the first 4 weeks and for the Oriental hybrids a temperature of approx. 15°C for the first 6 weeks. Therefore box cultivation with the use of a rooting room is advisable

• Ensure that plants maintain even transpiration and avoid excess transpiration by shading, and during clear weather conditions lightly spray with water a few times a day.

Abnormalities: Bud drop and bud desiccationAbnormalities: Bud drop and bud desiccationAbnormalities: Bud drop and bud desiccationAbnormalities: Bud drop and bud desiccation

Bud drop can occur from the time flower buds reach a length of 1 cm-2 cm. Buds turn light green in color and, at the same time, a constriction of the flower stalk junction with the stem occurs. Buds will subsequentely drop off. In spring, the lower buds are the first to be affected while the

higher buds drop first in the autumn. Bud desiccation can occur during all stages of development. Buds turn completely white and dry out. These dried buds sometimes fall off. Should bud desiccation occur during the initial stages of development these will later appear as minute white spots in the leaf axils. Cause Bud drop occurs when plants receive insufficient light. In light deficient conditions the stamens

in the bud produce ethylene causing the buds to abort. There is an increased risk of bud desiccation if rooting conditions are poor, e.g. too dry soil. Control

• Do not allow cultivars susceptible to bud drop to grow in poor light conditions

• To prevent bud desiccation, bulbs should not be allowed to dry out during planting. Ensure that bulbs root well and grow in the most favorable conditions possible, particularly as far as lighting and transpiration are concerned.

Nutrient deficiencies: Iron deficiencyNutrient deficiencies: Iron deficiencyNutrient deficiencies: Iron deficiencyNutrient deficiencies: Iron deficiency The leaf tissue between the veins of the young leaves is yellowish-green, particularly in rapidly

growing plants. The greater the iron deficiency the more yellow the plant will become. Cause

This abnormality occurs especially in calcium rich soils (high pH) and on light, silt soils or on sites with excess water. It can also occur if soil temperatures are too low. The deficiency is caused by a lack of plant absorbable iron. If only slight yellowing occurs it usually dissapears by

harvest.

The susceptible lily groups include the Oriental and Longiflorum hybrids and the cultivar

Connecticut King. Control

• Ensure that the soil is well drained with a sufficiently low pH (see pH). A good root system

also greatly reduces the risk of iron deficiency

• Depending on the susceptibility of the crop to iron deficiency, iron chelate should be added to soils with a pH higher than 6.5 before planting and, depending on the color of the crop, a second application after planting. If the color of the plant is still not

satisfactory, another application can be given after approx. 2 weeks

• With pH levels between 5.5-6.5, iron chelate should only be applied once or twice after planting depending on the color of the crop, to cultivars susceptible to iron deficiency

• The quantity of iron chelate to be applied depends on the pH of the soil and the time of

application. An iron chelate where the iron is bound to the organic compound EDDHA can be used, even in soils with a pH of 12 (all soils) and can continue to be applied right up to the last stages of cultivation. If the iron is bound to the organic compound DTPA then iron chelate can only be used in soils with a pH of ± 7 and can be applied until the flower buds

are visible. An excess of Fe-DTPA can cause black spots to occur on the foliage

• The dosage should be 2 g. - 3 g./m2 before planting (worked thoroughly into the soil) and a max. of 2 g. after planting, using a max of 1-1,5 g/m2 if a second application is needed

• The chelate can be applied either via the irrigation system or by hand mixed with dry sand

• To prevent leaf scorch, the chelate should be applied in the early evening to a moist crop when weather conditions are dull. Thorough washing off is essential

• Use or make sure to use a test application of iron chelate when applying to new cultivars!

Nutrient deficiencies: Nitrogen deficiencyNutrient deficiencies: Nitrogen deficiencyNutrient deficiencies: Nitrogen deficiencyNutrient deficiencies: Nitrogen deficiency Nitrogen deficiency results in the whole leaf becoming lighter in color and this is often more noticeable when plants are about to bloom. The plant often seems rather slight in appearance. Soils with a low nitrogen level produce a crop with stems which are lighter in weight and have less flower buds. Post-harvest foliage will turn yellow more quickly.

Control

• Always apply sufficient quantities of nitrogen, preferably based on the results of a soil sample

• If a nitrogen deficiency is diagnosed during cultivation apply an additional application of rapid-action nitrogen fertilizer. However, bear the risk of leaf scorch in mind during application and make sure the crop is always washed off thoroughly.

10. Selection of cultivars10. Selection of cultivars10. Selection of cultivars10. Selection of cultivars IntroductionIntroductionIntroductionIntroduction

New cultivars from the various lily groups are introduced onto the market every year. This is in itself not a bad strategy as it increases the uses for lilies. For the flower grower, it is difficult to make a choice between the many new and existing cultivars. However careful selection is crucial

to the economic performance of the crop. The qualities and cultivation data of a large number of cultivars as indicated in the tables may be of help to the grower when making this selection. The supplier will also be only too pleased to be of assistance. When making a specific selection there

are a number of important aspects to consider. These aspects are related to either the lily group or the cultivar. Group selectionGroup selectionGroup selectionGroup selection

The following points should be considered when choosing between the various lily groups.

• The financial aspect. For example the costs involved in buying some of the cultivars from the Oriental hybrid

groups are high compared to the purchase of lilies from the Asiatic group.

• Weather conditions. Asiatic hybrids are more susceptible to insufficient light than other groups. Oriental and

Longiflorum hybrids require higher minimum temperatures than Asiatic hybrids.

• Supply from stock. It is not always possible to store bulbs from the Oriental and Longiflorum hybrids for the same length of time, which means that supplies of all the cultivars in these groups are

not always available in the autumn.

• Growing period. On average Asiatic hybrids have a considerably shorter growing period than lilies from the other groups.

• Sales potential.

Oriental hybrids are bulkier than Asiatic hybrids and often exude a penetrating scent. Longiflorum hybrids are often considered funeral flowers.

• Plant familiarity. For the grower, unfamiliarity with a particular group could involve risks when having to make the right cultivation decisions. Therefore it is important to ask the supplier or the information advisory for information on unfamiliar groups. Alternatively evaluate a new cultivar yourself.

Cultivar selectionCultivar selectionCultivar selectionCultivar selection

• Color.

There is an extensive range of colors among Asiatic hybrids. However the range is more limited when it comes to the other groups

• Length. Extra length is often financially rewarding. However long cultivars are more likely to be

susceptible to light deficient conditions and require a longer growing period, making them less suitable for winter cultivation, whereas short cultivars are too short in the summer. Short lilies are the only cultivars used for pot lilies

• Growing period.

For a good programming schedule it is vital to have information on the growing period.

The growing periods shown in the tables are based on spring cultivation plus a

greenhouse temperature of approx. 14°C. During the summer, the growing period will be considerably shorter but will become increasingly longer in the autumn. During the early spring period, old harvest bulbs are used instead of new harvest bulbs because old bulbs come into flower more quickly and flower more evenly.

• Number of buds and presentation. A minimum requirement of the Asiatic and Oriental hybrids is the presence of five buds on every cut stem. If the buds are extremely large, then 3-4 buds per stem will be sufficient. Presentation is also important. Cultivars with smooth buds that are large and

well colored at the closed bud stage are preferred. Too much foliage which hides the flowers is less acceptable

• Sturdiness.

The firmness of stems can vary a great deal with each cultivar. The time of year is also significant in determining how firm stems will be. Less sturdy cultivars will develop stems which are too weak when growing during the autumn and winter.

• Susceptibility.

Some cultivars e.g. Connecticut King, Sterling Star, Star Gazer can be susceptible to leaf scorch. Smaller bulbs are less susceptible. Cultivars from the Oriental hybrid group, Longiflorum hybrid groups and the cultivar Connecticut King are susceptible to iron deficiency.

• Light susceptibility. Cultivars susceptible to bud drop should not be planted when the bud development stage is reached during the dark winter months and should certainly not be planted in a heavily shaded greenhouse or where light admission is poor due to old or dirty plastic

film.

• Keeping quality and vase life. The keeping quality and vase life is a very important point to consider when selecting cultivars. Although it is not prohibited to grow cultivars which have a short vase life, it is

advisable (especially bearing customer satisfaction in mind) to select cultivars which are long lasting. Yellowing of foliage and buds which do not open satisfactorily are frequently occurring factors which reduce the ornamental value of lilies.

• The position of the flower.

Most Asiatic hybrids have erect flower buds. In other groups there are quite a number of cultivars with pendulous or lateral flower buds. Seen from a labour viewpoint there are some disadvantages to these cultivars as far as harvesting, grading, bunching and

transporting the flowers are concerned. The market potential for cultivars with pendulous or lateral flower buds is smaller.

• Bulb size. With each cultivar a choice must be made from the various bulb sizes available. Larger

bulb sizes generally produce longer and heavier stems with more flower buds and will flower somewhat earlier. However planting density will have to be reduced to obtain optimum cultivation results.

SelectionSelectionSelectionSelection The Manual, part 2 deals with specific characteristics and cultivation dates. It discusses the lily

cultivars according to lily groups for cut-flower and pot plant production. Based on this information the flower grower can make an informed choice.