Flower Bulbs

Infobox on Flower Bulbs
Example of Flower Bulbs
Facts
Origin	Mostly the Netherlands
Stowage factor (in m3/t)	-
Humidity / moisture	See text
Ventilation	See text
Risk factors	See text

Flower Bulbs

Description / Application / Shipment / Storage

Bulb production

In bulb cultivation, a distinction is made between spring-flowering and summer-flowering plants. Growers plant the small bulbs (the planting stock) from this first group that includes tulips, narcissi, hyacinths and crocus in the autumn. The flower bulb grower mulches the rows or beds of bulbs with straw to protect the bulbs during the freezing winter temperatures and/or to prevent the wind erosion of sandy soil. A hyacinth, for example, would freeze during a lengthy period of severe frost.

When the plants bloom in the spring, the grower will usually remove the flowers from the plants. The most important reasons for doing so are to prevent diseases and to encourage growth. Other aspects of cultivation include fertilising, irrigating, removing diseased plants and trueness to variety, and preventing disease. The summer months are the lifting period for spring-flowering bulbs in the period from half June until half July. The small flower bulbs are then separated from the larger saleable bulbs.

Summer-flowering plants such as dahlias, gladioli and lilies, are planted in the spring. The flower bulb grower lifts these bulbous plants before winter sets in, in the period from half September until half November. The cultivation methods are generally the same as for the spring-flowering types.

Flower bulbs are stored at a wide range of temperatures. Storage rooms are kept at temperatures from -2°C to +44°C. With all these different temperature treatments, Mother Nature can really be fooled. It is possible to encourage bulb production during the next growing season, to advance flowering or to retard it, to increase flower production, and even to control diseases. These kinds of treatments are used for flower bulbs throughout the bulb sector: among flower bulb growers, flower bulb dealers, special temperature treatment companies, bulb flower producers, etc.

In comparison with earlier days, the prices for flower bulbs have not risen. This is due to the advanced state of mechanisation combined with the development of large-scaled operations. Planting, applying and removing the winter mulch, deheading of the flowers, lifting, grading and even the traditional bulb peeling are mostly done by machine. This does not mean that labour problems don’t exist, however. In fact, next to the need to improve the environmental friendliness of the growing methods, this is one of the most important concerns for the bulb grower. Every year, it becomes more difficult to find temporary workers for the seasonal harvest peaks.

Environmental management

This may well be the most important concern for today’s bulb growers. Bulb growers are aware that the opportunities for applying crop control agents will only diminish. Permission to use these agents is being withdrawn, the quantities allowed are being reduced, and the permission to use them is subject to increasingly stricter regulations. The various organisations in the bulb sector have now joined the ”Milieu platform” (an environmental consortium for flower bulb growers). Within this consortium, organisations are launching initiatives intended to approach environmental problems in a balanced way. Continued reductions in the use of and dependence on chemical agents, fertilisers and energy are the major topics being addressed. Concrete agreements (covenants) have been made with the government in regard to limiting energy consumption and the use of chemical agents. Results of the environmental discussion include: spray-free zones along the drainage ditches, spraying permits, required inspections of field spraying, modified spraying techniques, keeping fertiliser records, requiring that animal manures be injected into the soil rather than spread on top of it, the growing cultivation of organically grown bulbs, etc.

Bulb flower production

The majority of the cultivated flower bulbs are used for flower production. All the production of iris, tulips, hyacinths, lilies, narcissi, etc, has been preceded by bulb cultivation. Some of this production is done by Dutch flower growers, but a large share of the flower bulbs produced in the Netherlands is sent to similar operations in other countries. Flower growing operations are also undergoing interesting developments. We can see increases in scale, automation and new production systems. New developments include the hydroponic production of tulips, hyacinths and irises instead of soil, and the use of mobile benches. The production processes of flower bulbs and bulb flowers are closely interrelated. After all, there can’t be one without the other, and you need bulbs to get flowers!

Commercial cultivation techniques

In nature, plants usually propagate by means of seed. The cultivation of flower bulbs, however, is not that dependent on propagation by seed. This type of propagation is used only for plants that are difficult to propagate in any other way or when other ways would be far too costly. When propagating by seed, however, it is crucial that the seeds of the parent plant are true to type, i.e. they will produce plants that look exactly (or almost exactly) the same as the parent plant. Examples of bulbs or corms that are propagated by seed are anemones, Winter aconite (Eranthis), ranunculus and Tigridia.

Plant breeding

Breeding by means of seed is indispensable for obtaining new varieties. This involves the crossing of plants with the intention of obtaining new and improved varieties. This activity has been – and still is – of the utmost importance in the flower bulb sector. The current tulip range is the result of more than four centuries of crossing efforts. If a modern tulip variety is propagated from seed, it will produce a multicoloured mixture of descendants, some of which have undesirable qualities! Due to the advances made in crossing techniques, it is increasingly possible to create crosses between species or varieties that would not have been possible in the past. This means that highly desirable qualities, e.g. in colour or habit characteristics, can now be achieved by means of crossing. Even more important is the fact that hopefully there will even be more luck in the future in increasing the plants’ resistance to diseases of flower bulbs. This is extremely important to reduce the use of crop protection agents!

Vegetative propagation

Fortunately, most bulbous plants can easily be propagated vegetatively by means of separation of the "daughter" bulbs from the main bulb (hyacinth) or by dividing the entire main bulb cluster (tulip) into several large and small bulbs. The great advantage of vegetative propagation is that all the desired characteristics will be transferred to the new flower bulbs. Just one tulip bulb of the planting stock will quickly produce two to four "offspring". The narcissus takes somewhat longer to multiply but still grows fast enough to be able to sell about half of the number of lifted flower bulbs. The fastest natural propagation is seen among the gladioli: one large gladiolus corm can produce dozens of small cormels (small corms) in a single growing season. For lilies and hyacinths, growers have to assist the natural multiplication process. Since hyacinths produce few small bulbs on their own, the base of the bulb is cut away or by cross-cutting to stimulate the production of new little bulbs. To speed up lily production, scales are removed from the flower bulb and given a special storage treatment so that each scale produces one or more small bulbs.

Propagation by means of tissue culture

If the normal propagation methods take too much time or if it is important to produce many bulbs of a new variety within a short time, the flower bulb grower can choose to use "test tube propagation". In tissue culture laboratories, small pieces of bulbs or plants are placed onto special growing media containing plant hormones which stimulate the production of new plantlets or small bulbs. Many lilies as well as zantedeschias are produced this way.

Favourite spring flowering bulbs

During the summer months, the spring-flowering bulb such as tulips, narcissi, etc. are lifted by the growers and delivered to the dealers. Export takes place from August to December.

The Tulip
Of all the bulbous plants, the tulip is the most important. Tulips have been extremely popular as cut flowers and garden plants for many centuries. In 2007, about 10,000 hectares were used for tulip bulb production. The tulip accounts for one-third of the total export value for bulbs. The number of varieties being cultivated is also huge. There are more than 3000 varieties registered, while the number being cultivated on a commercial basis is not more than 750. Tulips are classified into various groups based on their flowering period and shape. Some examples are single, double, fringed, lily-flowered and parrot tulips. There are also tulip groups for botanical tulips and their related varieties. For flower bulb production, the tulip is planted in the autumn (October) and lifted in the summer (June/July).

The Narcissus
The narcissus is in third place of the most cultivated bulbous plants and is grown on a total area of 1.700 hectares. The narcissus has always been a highly favoured bulbous plant and has earned a permanent place in the flower bulb sector. Still commonly cultivated are the trumpet and large-cupped narcissi, although there are many, many other interesting kinds of narcissi (or daffodils). In total, there are about 2000 registered varieties! Even so, only about hundred are commonly available. The colour for narcissi is predominantly yellow, but white, pink and orange occur, too. They are used for both planting in the garden or park and for cut flower production. Among the smaller narcissi, the cultivar known as ‘Tête-à-Tête’ is very popular and with almost 600 hectares in cultivation has even become the leading cultivar. The majority of these bulbs are used for forcing in small pots. For flower bulb production, narcissus bulbs are planted in the autumn (September) and lifted in the summer (July).

The Hyacinth
As one of the bulbous plants cultivated almost exclusively in the Netherlands, the hyacinth is another bulb with a long tradition in the flower bulb sector and has always been a favourite for forcing in pots during the winter months. During the last 30 years, more and more hyacinths have also been used as cut flowers. Planting them in gardens and parks has been done for centuries. Of all the bulbous plants, the hyacinth is most cherished for its fragrance. Its colours are predominantly pastel: pink, light blue, soft red, white, light yellow and light orange, but brighter colours such as purple and violet are available as well. The land under cultivation with hyacinths has gradually increased to the present 1.250 hectares. For flower bulb production, hyacinth bulbs are planted in the autumn (October) and lifted in the summer (June/July).

The Crocus
Of all the bulbous plants, this very early spring-flowering corm perhaps gives us the strongest feeling of springtime. With the first rays of sunshine, they stand wide open! Except for a modest number used in forcing pot plants, millions of these corms are used in parks and gardens. Cultivation has fluctuated around 525 hectares in recent years. As most people know, the colours for the crocus are blue, purple, white and yellow. In addition to the most commonly cultivated large-flowering crocuses, there are also small-flowering varieties. And some crocuses flower in the autumn. For production purposes, the corms are planted before winter (November) and then lifted early in the summer (June).

The Iris
Bulbous iris rather than rhizomatous types are probably best known for their unique flower shape comprised of their standards and falls. Of approximately 380 hectares devoted to their cultivation, by far the most of these varieties are blue. Nevertheless, there are also extremely lovely white, yellow and bicolour varieties. Iris are most used for the year-round production of cut flowers. This is done in the field under warmer conditions and otherwise in greenhouses. In the Netherlands, flower bulb growers plant their bulbs in the autumn (September/October). Lifting takes place in the summer (August).

Favourite summer flowering bulbs

The summer-flowering bulbs such as lilies, gladioli, etc. are lifted in September, October and November and then delivered to the merchandising chain through the month of January. After having received their temperature treatments, the saleable bulbs will be sent in early spring to the points of sale where consumers will buy them.

The Lily
Of all the bulbous plants, the lily has shown very considerable growth in terms of hectares cultivated in the last few decades. In 1960, it was being cultivated on just 160 hectares. Now, this figure has risen to 4200! The lily is responsible for 25% of the total export value for bulbs. Its increase in cultivation is primarily due to the new groups of lilies that have been developed for cut flower production. The lily has become a very popular cut flower throughout the world. One of the lily groups, known as the Asiatic Hybrids, offers lilies in orange, red, yellow, white and pink. Also favoured are the Oriental Hybrids with their large white, pink or red scented flowers. Lilies in the Longiflorum Group (including the white ones sometimes known as Easter Lilies) have been grown for a long time, but recent breeding efforts involving the crossing of these lilies with Asiatic Hybrids has produced certain new groups known as the LA-,OT-,LO- and OA Hybrids. These groups are becoming more and more important. In the Netherlands, lily bulb production involves planting the bulbs in the spring and lifting them again before winter. For the production of flowers, the bulbs can be planted throughout the year in many different climate zones, both in the field and in greenhouses.

The Gladiolus
The production of gladiolus corms covers about 900 hectares; this puts it in second place among the summer-flowering bulbs. In terms of the number of hectares used for its production, the gladiolus is close to the narcissus. The number of hectares has decreased somewhat, mostly due to the great interest in lilies. Traditionally, this very colourful bulbous plant has been used for cut flower production in countries with temperate and warm climates, as well as for planting in gardens. These very tall plants have bright, appealing colours: red, purple, yellow, orange and white. In recent years, breeding has considerably increased the colours and flower shapes available in the commercial assortment. For the production of corms (gladioli are not true bulbs), the growers plant the small corms and “cormels” in the spring (April) and harvest them in the autumn (Mid October/ mid November) when they have grown larger.

The Dahlia
Like the gladiolus, the dahlia is also known for its bright summer colours. The only colour not included in its spectrum is blue. Its array of shapes is extensive as is suggested by the names of the various dahlia groups: pompon, decorative, collar, anemone-flowering, cactus, etc. Of all the bulbous plants, the dahlia has the longest flowering period of all: several months. Of the more than 450 hectares planted, most of the tubers find their way to gardens and parks. A small percentage is grown for cut flower production. Growers plant cuttings in the spring (May) and harvest saleable tubers in the autumn (October).

The special bulbous plants
The special bulbous plants are included in both the spring-flowering and summer-flowering groups. This "miscellaneous" group of "other" bulbous plants just might be the most interesting, however. There are dozens (and maybe even hundreds) of them. The number of hectares used to cultivate them is about 500. Familiar representatives in this group are the Grape hyacinths, Fritillaria, Allium (ornamental onion), Anemone, Hippeastrum (amaryllis), Begonia, Scilla, Canna and Zantedeschia (Calla lily). They are planted in gardens and parks, sold in pots, or used as material for cut flower production. Sometimes, a bulbous plant from this group emerges as a major bulbous plant due to its popularity. This happened with the lily and may also occur again with Zantedeschias. The interest in this "trendy flower" is so great that it is being grown on much more land every year.

During the summer months, the spring-flowering bulbs such as tulips, narcissi, etc. are lifted by the growers and delivered to the dealers. Export takes place from September to December.

The summer-flowering bulbs such as lilies, gladioli, etc. are lifted in October and November and then delivered to the merchandising chain through the month of January. After having received their temperature treatments, the saleable bulbs will be sent in early spring to the points of sale where consumers will buy them.

Bulbous and Tuberous groups

The classification of ornamental geophytes into bulbous and tuberous groups:

Primary storage and tissue groups	Type	Subclass	Taxa
A. Bulbous group
Scales and leaf bases	Bulb	Dicotyledonae Monocotyledonae	Oxalis cernua Most Allium species, Amaryllis belladonna, Camassia, Chionodoxa, Endymion, Eucharis, Eucomis, Fritillaria, Galanthus, Galtonia, Haemanthus, Hippeastrum, Hyacinthus, Hymenocallis, Iris hollandica, Iris reticulate, Iris xiphiodes, Ixiolirion, Lachenalia, Leucojum, Lycoris, most Lilium species, Muscari, Narcissus, Nerine, Ornithogalum, Polianthes, Puschkinia, Scilla, Tulipa, Urginea, Zephyranthes.
Basal plate (stem)	Corm	Dicotyledonae Monocotyledonae	Liatris Acidenthera, Babiana, Colchicum, Crocosmia, Crocus, Erythronium, Freesia, Gladiolus, Ixia, Sparaxis, Tigridia, Triteleia
B. Tuberous group
Stem	Tuber	Dicotyledonae Monocotyledonae	Some Anemone species, Eranthis Caladium, Gloriosa, most Zantedeschia species
Roots	Tuberous	Dicotyledonae Monocotyledonae	Astilbe, Dahlia, Eremurus, some Oxalis species Ranunculus, Hemerocallis
Stem	Rhizome	Dicotyledonae Monocotyledonae	Achimenes, some Anemone species, some Oxalis species. Some Allium species, Agapanthus, Alstroemeria, Anigozanthos, Canna, Clivia, Convallaria, sime Iris species, some Lilium species, Scadoxus, Zantedeschia aethiopica
Hypocotyl	Enlarged Hypocotyl	Dicotyledonae Monocotyledonae	Begonia (Tuberous Hybrids), Cyclamen, Gloxinia None

Flower bulb production involves the cultivation of flower-producing bulbs, corms, tubers, and rhizomes. In true, bulbs, nutritional reserves are stored in fleshy scales that are parts of the plants’ underground storage organs. Good examples of true bulbs are tulips, hyacinths, irises, lilies and narcissi. The other geophytes (the scientific name for all these plants with underground storage systems)have different types of storage organs. Good examples are gladioli and crocuses (corms), dahlias (tubers) and certain irises (rhizomes).

Hippeastrum

Hippeastrum
An example of a true bulb consisting primarily of enlarged leaf bases. New bulbs continually develop from the centre with a cycle of four leaves and than an inflorescence. Bases of the leaves enlarge to become the scales that contain stored reserves. The oldest scales disintegrate.

Tulipa

Tulipa
An example of a tunicated bulb comprised primarily of annual replacement scale tissue. Longitudinal section represents the stage of development shortly after the bulb is planted in the autumn.

Lilium

Lilium
An example of a non-tunicated bulb comprised primarily of perennial scale tissue. Left: Outer appearance of an unplanted bulb of L. hollandicum. Right: Longitudinal section of a bulb of L. Longiflorum ‘Ace’, after the flowering stage of development, showing the old mother bulb scales and the new daughter bulb scales in the autumn at lifting time.

Gladiolus

Gladiolus
An example of a tunicated corm comprised primarily of enlarged stem tissue. Left: External appearance in the summer. Right: Longitudinal section showing solid stem structure in the autumn.

Caladium

Caladium
An example of a tuber comprised primarily of enlarged stem tissue. Tuber with six large dominant buds or sprouts.

Dahlia

Dahlia
An example of a tuberous root comprised primarily of enlarged root tissue.

Iris Germanica

Iris Germanica
An example of a rhizome comprised primarily of a specialised horizontal stem.

Cyclamen

Cyclamen
An example of an enlarged hyopocotyl storage organ

Storage spring bulbs

	Storage method	Temperature until planted °C.
Allium (large and small-flowering)	Dry and ventilated	23-20-17°C.
Allium cernuum, flavum, carinatum, ursinum	Ventilated, protect from drying out	9-5°C.
Amarcrinum	Dry and ventilated	5°C.
Amaryllis belladonna	Dry and ventilated	5°C.
Anemone blanda	Dry and ventilated, provide air circulation	17°C.
Brimeura (syn. Hyacinthus amethystina)	Dry and ventilated	23-20°C.
Camassia	Dry and ventilated	20-17°C.
Chionodoxa	Dry and ventilated	23-20-17°C.
Colchicum	As cool as possible, delivery early	9-(2)°C.
Corydalis, cava, solida	Dry and ventilated	9°C.
Crocus	Dry and ventilated	23-20-17°C.
Crocus (autumn-flowering)	Dry and ventilated, delivery early	9°C.
Eranthis	Dry and ventilated, prevent desiccation	9-5°C.
Eremurus	Protect from drying out	17-9-5°C.
Erythronium dens-canis	Protect from drying out	9-5°C.
Erythronium (other varieties)	Susceptible to mechanical damage	25-23-17°C.
Fritillaria imperialis	Ventilated, susceptible to mechanical damage	25-23-17°C.
Fritillaria meleagris	Protect from drying out, provide air ciculation	17-9°C.
Fritillaria michailovskyi	Protect from drying out, provide moderate air ciculation	17-9°C.
Galanthus	Protect from drying out	17°C.
Hippeastrum (syn. Amaryllis)	Dry and ventilated, 12 wks at 13°C, then 5°C (56°F is preparation, 41°F is storage)	13-5°C.
Hyacint (prepared)	Dry and ventilated	30-25-20-17°C.
Hyacint (not prepared)	Dry and ventilated	25-20-17°C.
Hyacinthoides (syn. Scilla campanulata)	Highly ventilated, susceptible to mechanical damage	20°C.
Iris latifolia (syn. Iris Anglica)	Dry and ventilated, control for aphids	20-17°C
Iris Hollandica	Dry and ventilated	(30)-25-20-17°C.
Iris reticulata, danfordiae	Dry and ventilated	23°C.
Ipheion uniflorum	Requires plenty of air circulation; store in shallow layers	20-17°C.
Ixiolirion	Dry and ventilated	23-17°C.
Ixia	Dry and ventilated	25-23°C.
Leucojum aestivum	Dry and ventilated	20-17°C.
Leucojum vernum	Protect from drying out	9-5
Muscari	Dry and ventilated	23-20°C.
Narcis	Dry and ventilated	20-17°C.
Ornithogalum (large-flowering), e.g. saundersiae, arabicum	Dry and ventilated	25-23°C.
Ornithogalum (small-flowering)	Dry and ventilated	20-17°C.
Oxalis adenophylla	Dry and ventilated	20-17°C.
Puschkinia	Dry and ventilated	23-20-17°C.
Scilla siberica	Dry and ventilated	25-23-20°C.
Scilla peruviana	Dry and ventilated	23°C.
Sparaxis	Dry and ventilated	25-23°C.
Tulipa	Dry and ventilated	23-20-17°C.
Trteleia (syn. Brodiaea)	Dry and ventilated	23°C.

Guidelines for storing flower bulbs This temperature storage chart has been drawn up for dry sales! Modified preparation temperatures can be necessary for purposes of flower production in order to time the flowering periods.

General remarks:

• Storage temperatures apply to properly dried, clean products
• For the forcing sector and for different planting and flowering periods, modified temperature treatments may be necessary
• It may be important to ask the supplier about previously applied storage temperatures
• A decreasing series of temperatures means that the highest temperature should be applied at the beginning of the storage period and that the lower temperatures should be applied towards planting time
• For spring-flowering bulbs, a storage period lasting to planting time is assumed, i.e. no later than mid-December and, in any case, before freezing winter temperatures set in
• If protecting from desiccation is mentioned, it would be advisable to use a filling material, and this should be added to the packaging in any case
• "Dry and ventilated" means to use ventilated packaging
• Pay special attention to aphid control

R.H. = Relative Humidity

Storage summer bulbs

	Storage method	Temperature until planted °C.
Anemone coronaria	Dry and ventilated, constant temperature	17-15°C.
Begonia	Protect from drying out, provide air circulation	9-5°C.
Canna	Protect from drying out, no air circulation	12-8°C.
Cyclamen	Protect from drying out	9°C.
Dahlia	Keep from compacting, avoid draughts, no air circulation	9-7°C.
Eremurus	Protect from drying out	9°C.
Eucomis	Dry and ventilated	13-9°C.
Freesia	Airy, RH 80%	25°C.
Galtonia candicans	Dry and ventilated	20-17-13°C.
Gladiolus	Dry and ventilated	17-9-5°C.
Gladiolus callianthus 'Murielae'(syn. Acidanthera)	Dry and ventilated	20°C.
Gloriosa rothschildiana	Protect from drying out	20-17°C.
Hippeastrum (syn. Amaryllis)	Dry and ventilated (this slows development)	5°C.
Hymenocallis (syn. Ismene)	Dry and ventilated	25-23-17°C.
Iris Hollandica	Dry and ventilated, storage at 30°C will slow development	30-17°C.
Ixia	Dry ventilated, RH 70-80%	25-23°C.
Liatris	If to be stored longer than 3 months: freeze at -2°C/35,5-32°F.	2-0°C.
Lilium	If to be stored longer than 3 months: freeze at -2°C/35,5-32°F.	2-0°C.
Nerine	Dry and ventilated	9°C.
Ornithogalum thyrsoides, dubium	Dry with a highly ventilated container	30-25°C.
Oxalis deppei, regnelli, triangularis	Dry and ventilated	5-3°C.
Ranunculus	Dry and ventilated, constant temperature	17-15°C.
Sauromatum venosum (syn. Arum cornutum)	Dry and ventilated, store frost-free	5-2°C.
Sparaxis	Dry and ventilated, RH RV 70-80%	25-23°C.
Sprekelia formosissima	Dry and ventilated, 6 weeks at 20°C., then 9°C (20°C. is preparation, 9°C. is storage)	20-9°C.
Tigridia pavonia	Dry and ventilated	5-2°C.
Tritonia	Dry and ventilated	25-23°C.
Triteleia (syn. Brodiaea)	Dry and ventilated, RH 70-80%	25-23°C.
Zantedeschia aethiopica	Provide a little air circulation	13-7°C.
Zantedeschia (other cultivars)	Dry and ventilated	13-9°C.
Zephyranthes	Dry and ventilated	20°C

Guidelines for storing flower bulbs This temperature storage chart has been drawn up for dry sales! Modified preparation temperatures can be necessary for purposes of flower production in order to time the flowering periods.

General remarks:

• Storage temperatures apply to properly dried, clean products
• For the forcing sector and for different planting and flowering periods, modified temperature treatments may be necessary
• It may be important to ask the supplier about previously applied storage temperatures
• A decreasing series of temperatures means that the highest temperature should be applied at the beginning of the storage period and that the lower temperatures should be applied towards planting time
• For spring-flowering bulbs, a storage period lasting to planting time is assumed, i.e. no later than mid-December and, in any case, before freezing winter temperatures set in
• If protecting from desiccation is mentioned, it would be advisable to use a filling material, and this should be added to the packaging in any case
• "Dry and ventilated" means to use ventilated packaging
• Pay special attention to aphid control

RH = Relative Humidity

No liability whatsoever is accepted for the consequences that result from the use of this information.

Frost damage Minor frost damage before the plants emerge generally retards growth and cause the plants to grow twisted. The basal plates are glassy and pale grey. Severely frost-damaged plants do not emerge.

Generally frost damage occurs when the bulbs are stored for some time at temperatures below -2°C and gradually becomes more serious the longer the bulbs are stored at this temperature. At temperatures lower than -5°C, serious damage occurs even after a few hours.

Diseases and insects
All users of flower bulbs must be familiar with the diseases and insects that affect each species. There are many pests, but usually there are only a few major ones for each species. Knowledge of the major pests and the conditions controlling their development can assist in either eliminating and/or minimizing their effects during postharvest storage.

Bulb flower production: what does this cover ?
Bulb flower production involves the production of flowers by a floriculturist. Actually, the term “bulbs” also includes corms, tubers, rootstocks and rhizomes. Another commonly used phrase is “the forcing of flower bulbs”. Unfortunately, however, this phrase is not always applied correctly; after all, forcing is merely getting bulbs to come into flower earlier – before their natural flowering period outside. But besides getting bulbs to flower earlier than their natural flowering period, the process can also be carried out later. Good examples of forcing are the 5° and 9˚C tulips that are forced during the winter (whilst any tulip bulbs outside will not flower until spring) and what are known as “ice tulips” that are not brought into flower until the next autumn! Many bulbous plants enter a dormant period after their growth period. To get them to flower earlier than they would under natural conditions, they will have to be subjected to artificial cold and warm periods to break this dormancy. If these periods are cut short or skipped altogether, flowering results will be disappointing or the greenhouse period will have to be greatly extended (the extent of these negative consequences depending on the type of bulbous plant). For certain production methods and their related procedures, the temperature treatment needed to break dormancy will be carried out by the flower bulb supplier in the Netherlands. In other cases, the floriculturist will do this.

Commercially, flower bulbs usage can be divided into two groups. The first group is the ‘Planting Stock’. These are the propagation materials and are generally grown by specialized bulb growers. The second group is the ‘Commercial Bulbs’, which are primarily used for: forcing either as fresh-cut flowers or as potted growing and flowering plants; indoor or outdoor container plants; outdoor fresh-cut flower production; and garden and landscapes.

Optimum postharvest storage conditions in combination with ideal bulb growing conditions and procedures are required to: 1) control (prevent, retard or accelerate) the flowering process from floral initiation to anthesis; 2) assist in controlling certain diseases and insects; and 3) preventing physiological disorders. For each species, it is important to know: 1) precisely when flower initiation occurs; this can be before harvest (e.g. hardy narcissus), during postharvest storage (e.g. tulips and hyacinths) or after planting (e.g. Easter lily); 2) the length of time required for floral development from initiation to anthesis can be a few weeks to several months; 3) the optimal temperatures required to control the entire flowering process; this can range from -2°C to +34 °C, depending on the species, etc.; 4) the sensitivity of the bulb species and/or cultivar to ethylene, which ranges from none to very sensitive; 5) the ventilation requirements, which range from none to high; 6) the moisture requirements, which range from none to high; and 7) the specific diseases and/or insects than can be controlled during the postharvest storage period, which can range from none to several.

Thus, all shipping containers must be able to provide the proper temperature, ventilation, and moisture requirements for the bulbs. Temperature is the most important factor controlling the growth and development and flowering processes of flower bulbs. When the taxa require ventilation, it is essential that the flower bulbs receive proper air circulation and exchange during all periods of postharvest storage. Thus the application of these requirements must begin immediately after the grower harvests the bulbs and continue during transportation and subsequent handling by the wholesaler, forcer and/or retailer. The exact ventilation requirement is generally very specific. In general, ventilation rates must be adapted to the storage temperature, i.e. when higher temperatures are used, higher rates of ventilation must be used. There are two basic considerations for the moisture level for bulb storage. The first is to provide the optimum moisture level, which will prevent desiccation of susceptible bulbs. Thus, materials such as moist peat or wood shavings are used in combination with the various packaging materials, e.g. polyethylene. The second is the control of RH during storage or transportation, which can minimize root development and prevent the development of diseases such as Penicillium. In addition, this approach is an important technique to minimize the use of fungicides either prior to and/or after shipping. Since the registration of fungicides varies with each country and is always subject to change, users must consult with their appropriate governmental agency to determine which pesticides are approved.

With the exception of Dutch Iris, non-planted flower bulbs must not be exposed to ethylene. Most bulbs are physiologically sensitive to ethylene levels of 0,1 ppm and higher. In general, when the flower has been formed and is immature, this plant growth regulator causes either floral abnormalities or complete flower abortion. For severe sensitive bulbs, e.g. tulips, it is advisable to have the storage rooms analyzed for ethylene.

All users of flower bulbs must be familiar with the diseases and insects that affect each species. There are many pests, but usually there are only a few major ones for each species. Knowledge of the major pests and the conditions controlling their development can assist in either eliminating and/or minimizing their effects during postharvest storage. The production/forcing methods used for the most familiar bulbous plants are summarily presented on the following pages. Because of the number of cultivars and their varied usage, more details cannot be provided since the precise requirements for all taxa are complex.

The need and length of cold storage for bulbs/tubers depends on where the bulbs are grown and for what purpose. It is, therefore, not always possible to make hard and fast rules as to the period of storage. With many bulbs/tubers, cold storage immediately after digging (lifting) and curing is unnecessary during the usual period of use or sale, because they remain in dormant condition for a time, even at fairly high temperatures and humidity. When the rest period is nearly over, however, it usually is necessary to store them at a lower temperature to prevent sprouting and at a relative humidity low enough to prevent rooting but high enough to retard moisture loss.

Basic concept of flower bulb forcing
Forcers must use controlled environmental conditions to regulate the growth and development and flowering of the bulbs. This system of greenhouse growing is called ‘Forcing’. Fundamentally, the process is very easy. However, to successfully carry it out, forcers must have a basic understanding of the principles underlying flower bulb forcing. They are derived from a knowledge of:

1) The origin and morphology of the bulb species. 2) The growth and development and flowering cycle of the species. 3) The influence of environmental factors on the growth and development and flowering cycle of the species.

Origin of the species
Most ornamental flower bulb species originate between 23° to 45° North and South latitudes. Many of the species are indigenous to the Mediterranean region across Asia Minor to China, while others are from America, South Africa, or South America. A climate that predominates in many of these regions consists of cool-moist winters followed by warm-dry summers. A yearly climatic cycle based on temperature is termed ‘Annual Thermoperiodism’. This alternation of temperatures forms the basis for ‘Rooting Room’ forcing and is illustrated by the tulip (see below drawing). In some areas, there are not only annual seasonal changes in temperature, but also wet and dry seasons. Thus, moisture is extremely important for controlling growth of certain species. In addition to temperature and moisture, most flower bulbs are highly responsive to light intensity, photoperiod, and light quality. Clearly, each flower bulb responds to specific environmental factors based on its origin.

Environmental factors
Scientific research and astute observations by individuals have demonstrated that these are at least 12 factors that influence the growth and development of bulb species. Each is very important at some precise stage of growth and development. In general, however, temperature integrated over time is the most important.

Lack of physiological dormancy
True physiological dormancy does not exist in flower bulbs. They act like ‘Biocomputers’ and are continuously undergoing internal change as they monitor their environment. Thus, commercially they must be handled with care (properly) at all times.

Phases of bulb forcing
To integrate the knowledge of the flower bulb growth and development and flowering cycle and the effects of environmental factors, the forcing systems for ‘Rooting Room’ and ‘Non-Rooting Room’ bulbs have been divided into five distinct phases. They are:
1) Production phase
2) Programming phase
3) Greenhouse phase
4) Marketing phase
5) Consumer phase

1) The ‘Production Phase’ encompasses all aspects affecting the growing of high quality bulbs suitable for forcing or outdoor flower production. ‘Quality bulbs’ must be true-to-type and must flower when properly forced or grown outdoors. Many books have been written on bulb growing. In practice, it must be assumed that all production practices will be carried out by knowledgeable bulb growers.
2) The ‘Programming Phase’ :

Phase	Programming			Greenhouse
Seasons	Summer	Autumn	Winter	Spring
Growth and development processes	Harvesting of the bulbs. Preplanting storage for floral development	Planting and rooting under cool-moist conditions	Mobilisation for flowering under low temperatures	Flower stalk elongation and flowering under warm temperatures

Figure:Annual growth and developmental cycle of a flowering tulip. A) Harvested cluster; B) Separated ‘A’ bulb; C) Mother bulb with highly developed root and shoot primordial prior to planting; D) Rooted bulb in an overwintering environment; E) Mother bulb at anthesis (flowering), small shoot is the ‘H’ bulb.

Each year the ‘Physiological Maturity’ of the harvested bulbs varies. It is highly dependent upon the prevailing weather conditions of the production season. Sometimes, the weather will be ‘Average’ and the forcing season is ‘Normal’. In other years, ‘Very Mature’ bulbs are produced and the forcing season is ‘Easy’. Conversely, when the bulbs are ‘Physiologically Immature’, the forcing season is ‘Hard’. When extreme seasonal variations occur during the ‘Production Phase’, changes must be made in the forcing schedules, especially in ‘Hard’ forcing years. Also, under extreme climatic conditions some soil-borne diseases, e.g. Fusarium and Penicillium, can become serious carryover problems for forcing.

When serious forcing problems are anticipated due to the bulb production season, the flower bulb supplier must advise the forcer of the situation. Communications on the subject are essential.

After being harvested, all flower bulbs must be packed and stored according to their requirements. Generally, all harvesting, grading and the immediate postharvest temperature treatments are carried out by the bulb grower. Subsequently, the exporter must store them properly prior to shipping. Lastly, the bulbs must be properly transported.

The ‘Programming Phase’ begins as soon as the bulbs are harvested. Initially, warm temperatures given after harvest control the early stages of flower development. With the exception of daffodils (Narcissus) in which flowers are initiated prior to harvest, the immediate postharvest temperatures control the rate of flower initiation and formation in tulips and hyacinths and ‘Specialty Bulbs’, e.g., Crocus, Iris reticulate, Leucojum aestivum, Muscari armeniacum and Scilla tubergeniana (S. mischtschenkoana). Thus, they are used to either accelerate or delay the flowering process for forcing. After the flower(s) is completely formed, but not mature, spring flowering bulbs require a low temperature treatment. This requirement is defined by the number of continuous cold-weeks required by the specific cultivar for the specific flowering period. The cold-weeks must be continuous and the dry cooling (‘Precooling’) weeks and rooted and cooled weeks are added to provide the total cold-weeks used. This ranges from 10 to 13 weeks at 9°C for ‘Prepared’ hyacinths, to 18 – 20 weeks at 0°/9°C for tulip cultivars used for very late forcings. The exact programming temperatures and flowering periods are highly cultivar dependent. In addition, all cultivars of each bulb species are not suitable for forcing while those that are forced are best suited only for specific uses and flowering periods.

3) Greenhouse phase
After the rooting and cooling requirements have been satisfied, the bulbs are transferred to the ‘Greenhouse Phase’. Warm temperatures are used to elongate the flower stalk(s) and expand the leaves to produce either fresh cut flowers or flowering plants. Regardless of the forcing system used, the goal of the ‘Greenhouse Phase’ is to produce a high quality marketable plant in the shortest number of days. Thus, proper control of temperature, fertilization, moisture, and other factors is essential.

4) Consumer phase
This is a very important phase of any forcing system. Consumers must be satisfied with the performance of the products. Not only must the specific crop be evaluated but also the cultivars. Cultivars usually vary in their vase-life and/or potted flowering life.

5) Marketing phase
The ‘Marketing Phase’ determines the product to be forced and sold. Regardless of whether the product is a flowering potted plant, a fresh cut flower, a growing potted plant or a bulb garden, it is important that the product be sold at the proper stage of development.

Various aspects on several flowerbulbs

Tulip, Hyacinth, Narcissus, Lilies, Gladioli, Iris, Zantedeschia (see below)

Tulip

General aspects
The tulip belongs to a group of bulbous plants that need a cold period to ensure flowering and development of sufficient stem length. In regions where temperatures are sufficiently low in winter, tulip bulbs planted in the field undergo this cold period naturally. Research has shown that tulip bulbs which receive their cold treatment before the winter months can be brought into flower before their natural flowering period. This method is called forcing. Depending on the regional climate in which the tulip bulbs are produced, flowering as early as December is possible. The climate influences the development of the new tulip flower shoot until the bulbs are lifted and, provided the bulbs are not treated further in a cold room, even afterwards. As well as advancing development, the flowering time of tulips may also be delayed. Tulip flowers have been marketed as early as September, October and November for some years now. These so-called ice tulips are produced from bulbs that are stored at low temperatures for an extended period of time. In order to advance the cold period, the bulbs are subjected to a number of temperature treatments. It is vital that the bulbs are not cooled until the flower has developed fully in the bulb, mostly even later.

For very early forcing, most cultivars are given 34°C for 1 week immediately after lifting. Subsequently, they are stored under dry and well-ventilated conditions at 17°C to 20°C. It is very important to be able to identify the stages of flower initiation prior to being pre-cooled at 5°C to 9°C. For medium and late forcing, bulbs are placed at 17°C to 23°C prior to planting at low temperatures. Bulbs are also grown in the Southern Hemisphere for planting in the autumn in the Northern Hemisphere. This eliminates the need and effects of long storage periods.

Cooling temperatures for tulips are 9° C and below. Different temperature will yield different results. For example, ‘high’ as opposed to ‘low’ temperatures will produce:

• Shorter flower stems
• Larger flowers
• Longer greenhouse period
• Less risk of flower blast (in early forcing)
• Faster growth of stems and roots
  
  

There are three methods to bring tulips into flower: forcing in trays, cultivation in the border soil of the greenhouse and delaying in trays (ice tulips). Each of these methods relies on one or more cold treatments.

Forcing in trays: 9°C
Bulbs are planted in trays which are then stored in a rooting room or a plunging bed. This method, whereby the bulbs receive the entire cold period in the rooting room or naturally outside, produces so-called ‘uncooled tulips’. Part of the cold treatment can also be given to the dry bulb (9°C tulips) before it is planted in a box to continue and complete its cold treatment.

Forcing in trays is the most commonly used forcing method for tulips. There are a number of reasons for this, including:

• Forcing in trays allows for better planning, without being too dependent upon outside temperatures
• Forcing in trays allows better labour planning
• Relatively few diseases due to the low temperatures in the rooting room. This is an important advantage in view of likely future restrictions or even ban on the use of pesticides.
• Reduced energy consumption due to shorter periods in the greenhouse
• Forcing in trays achieves a higher production of tulips per m² per forcing season
  
  

Forcing in the border soil of the greenhouse
Dry bulbs receive the entire cold period while stored in a cold room at 5°C or 2°C. Immediately following the cold treatment, the bulbs are planted in the greenhouse, ready for flower production to start.

Delaying flowering in trays: Ice tulips
Ice tulips are planted in trays in November, where they remain to root for 2 to 4 weeks at 9°C. After the rooting phase, the trays are frozen and stored at -1,5°C to -2°C. In order to prevent trays from drying out, they are usually wrapped in plastic. From September, trays are generally placed in the greenhouse or in a cool place outside where the bulbs are to flower. A limited range of tulips is forced into flower in autumn in this manner. Unfortunately, both the flower and the keeping quality of these tulips leave a lot to be desired.

Using bulbs produced in the Southern Hemisphere for 9°C tulips
These bulbs are delivered in May and will already have received part of their required cold period during their transport from the Southern Hemisphere. After receipt, the bulbs should be boxed up immediately and stored for 4 weeks at 7˚C. Next, the temperature in the storage room can be reduced to 0˚C until the housing date. By providing a greenhouse temperature of 14 - 15˚C, flowering can be expected within 15 to 18 days. Depending on the greenhouse climate and the cultivar, flowers can be produced from October to mid- December.

Transport advice

Temperature	-0,5°C to 0°C.
Relative humidity	65% to 75%
Air freshening	0 to 90 cbm/hr
Max. storage life	150 to 180 days
Ethylene production	Very low
Ethylene sensitivity	High

Note: Tulip bulbs may be shipped at any temperature between +5°C and +22°C, depending on the bulbs’ stage of life (= season), variety, and receiver’s purpose of use.

Storage disease(s)
The major storage diseases are Fusarium and Penicillium. Normally Fusarium infections begin in the field and continue during the postharvest storage. There are substantial differences in cultivar susceptibility, but it is important to reduce the number of infected bulbs in storage because of the ethylene they produce. This can lead to flower abortion and abnormalities. Thus the bulbs must be routinely inspected and the rooms monitored for ethylene. Levels in the storage rooms must not exceed 0.1 ppm.

Hyacinth

General aspects
Two types of commercial bulbs for forcing are available for greenhouse forcing as either potted plants or fresh cut flowers. The first is ‘Prepared Bulbs’, which are used for very early forcing. After being harvested (in early July), the bulbs are stored under dry and highly ventilated conditions for 2 weeks at 30°C, followed by 3 weeks at 25°C, and then 23°C until the uppermost floret reaches the correct stage. Subsequently, they are stored at 17°C until planted. ‘Regular Bulbs’, which are used for medium and late forcing, are given 25°C followed by 4 weeks at 17°C prior to planting.

Prepared and unprepared hyacinths in pots
Depending on the required flowering period and cultivar, the bulbs receive a cooling treatment at 9°C for 8 to 12 weeks. This cooling treatment is given after the bulbs have been planted in pots. Once potted, the cooling treatment takes place in the rooting room at the floriculturist’s premises. After the cooling period has been completed, the pots are taken from the rooting room and placed in the greenhouse. At a greenhouse temperature of 25° (for Christmas flowering) to 18°C, the pots are ready for sale within 1 to 2 weeks (the warmer, the earlier). Depending on the preparation and the cultivar, the pots are ready for sale from December to April.

Prepared and unprepared hyacinths for cut flower production
Depending on the required flowering period and cultivar, the bulbs receive a cooling treatment at 9°C for 10 to 15 weeks. This cooling treatment is given after the bulbs have been planted in boxes. Once planted, the cooling treatment takes place in the rooting room or on the standing ground at the floriculturist’s premises. After the cooling period has been completed, the boxes are taken from the rooting room or standing ground and placed in the greenhouse. At a greenhouse temperature of 20° to 18°C flowers will be ready for harvest in 2 to 3 weeks (the warmer, the earlier). After harvesting the whole plant, including the bulb, part of the base plate of the bulb just below the stem is left attached to the stem to encourage the proper opening of the florets. Depending on the preparation and the cultivar, flowers can be produced from mid-December to April.

Transport advice

Temperature	-17°C to 20°C.
Relative humidity	65% to 70%
Air freshening	90 cbm/hr
Max. storage life	60 to 150 days
Ethylene production	Very low
Ethylene sensitivity	High

Storage disease(s)
The major storage diseases for commercial sized hyacinth bulbs is Penicillium.

Narcissus

General aspects
Commercial bulbs for early forcing are given 1 week at 34°C followed by 17°C. All the other bulbs are provided 17°C to 20°C. Like most other bulbous plants, most narcissi require a cold period to ensure rapid growth and flowering. A temperature of 9°C provides sufficient cold whereas a cold period of 5°C to 2°C will produce shorter crops.

Forcing in boxes ; nine-degree (pre-cooled) and non-cooled narcissi
Depending on the required flowering period and cultivar, the bulbs receive a cooling treatment at 9°C for 14 to 18 weeks. The cooling treatment is applied after the bulbs have been planted in boxes. The boxes are then placed in the rooting room at the floriculturist’s premises. Part of the cooling treatment can, however, be applied to the dry bulbs (nine-degree narcissi) before planting the bulbs in boxes; once planted, the cooling treatment continues until completed. Then the boxes are taken from the rooting room and placed in the greenhouse. At a greenhouse temperature of 18° to 16°C, flowers are ready for harvest in 2 to 4 weeks (the warmer, the earlier). Depending on the climate and cultivar, flowers can be produced from December to the end of March.

Forcing in pots; nine-degree (pre-cooled) and non-cooled narcissi
Depending on the required flowering period and cultivar, the bulbs receive a cooling treatment at 9°, 5° and then 2°C for a total of 14 weeks. The cooling treatment is applied after the bulbs have been planted in pots, the pots being placed in the rooting room at the floriculturist’s premises. The cooling treatment is applied to dry bulbs (nine-degree narcissi) of long-stemmed narcissi for 6 weeks before potting-up and completing the cooling treatment. After the cooling period has been completed, the pots are taken from the rooting room and placed in the greenhouse. At a greenhouse temperature of 15° to 18°C, the pots are ready for sale in 1 to 2 weeks (the warmer, the earlier). Depending on the climate and cultivar, the pots are ready for sale from December to the end of March.

Forcing in the greenhouse border soil; nine-degree (pre-cooled) and non-cooled narcissi
For this production method, the bulbs receive most or all of their cooling period naturally in the greenhouse border soil. If part of the cooling is applied to dry bulbs (i.e. unplanted), this is done in a cold store at 9°C (for nine-degree narcissi). Once the cooling period has ended, a greenhouse temperature of 18° to 16°C is maintained; the flowers are ready for harvest in 2 to 4 weeks (the warmer, the earlier). Depending on the climate and cultivar, flowers can be produced from December to the end of March.

Transport advice

Temperature	-13°C to 24°C.
Relative humidity	70% to 90%
Air freshening	90 cbm/hr
Max. storage life	60 to 120 days
Ethylene production	Very low
Ethylene sensitivity	High

Storage disease(s)
The major storage diseases are Fusarium and Penicillium. To control Fusarium in the ‘Planting stock’, approved fungicides are added during a hot-water-treatment. This treatment also controls nematodes and bulb flies.

Lilies

Postharvest storage and transport requirements
To properly flower lilies, the (Commercial) bulbs must be packed in moist peat, wrapped in polyethylene, and packed in trays which are used for storage and shipping. Subsequently they require at least 6 to 8 weeks at 2°C before being planted for early forcing. For late and year-round forcing, the bulbs are ‘frozen-in’ at -1°C to -2°C after being pre-cooled for 6 to 8 weeks. During bulb transportation the bulb shoot can be easily frozen and it is more cold-sensitive than the vegetative scales. The bulb must be dissected to determine if freezing damage occurred during storage. Blistering of the scale epidermis may be observed and it is associated with small patches of ice under the epidermis. It is known that unplanted and unprotected lily bulbs are killed by temperatures below -5°C.

Cut flower production of bulbs planted in the greenhouse border soil and in the field
For greenhouse production, bulbs from the new harvest are planted directly into the greenhouse border soil, the ideal greenhouse temperature is 14° to 16°C all-year-round. Depending on cultivar, temperature and season, lilies will flower within 10 to 20 weeks. A large percentage of the cultivars can be delivered and planted year-round if stored at temperatures between 0.5° and -2°C. Depending on the climate and cultivar, lilies can also be planted outside in the field. During the summer months, shading protection will be required both in the greenhouse and outside. During light-deficient months, supplementary greenhouse lighting is recommended to prevent flower desiccation. Depending on the climate and cultivars, year-round flowering is possible under protection.

Cut flower production in boxes in the greenhouse
Production is very similar to growing in the greenhouse border soil. Instead of planting in the border soil, however, bulbs are planted in boxes. For optimum rooting boxes are placed in a rooting room at 5° to 12°C; maintaining a lower temperature means slower elongation and the possibility of planting earlier. After rooting, the boxes are placed in the greenhouse. This production method is frequently used for Oriental Hybrid group cultivars for year-round cultivation, but is also used for the initial rooting phase during warm periods of the year. Depending on the climate and cultivars, year-round flowering is possible.

Producing lily flowers from bulbs grown in the Southern Hemisphere
These lilies are usually cultivars in the Oriental Hybrid Group. Compared to Dutch bulbs, these bulbs have been lifted six months later. If planted in the Northern Hemisphere in the autumn, this means that their storage period will have been six months shorter. And a shorter storage period means a crop of higher quality. These bulbs can be planted in the greenhouse soil or in boxes from 1 October to the end of January.

Pot lilies
For pot lilies, bulbs of genetically short cultivars are usually used. Bulbs from the new harvest are planted in pots from December through to December next year and housed in the greenhouse, the ideal temperature being 14° to 16°C. Depending on the cultivar, temperature and season of the year, pots will be ready for sale in 9 to 16 weeks. A large percentage of the cultivars can be delivered and then planted year-round if stored at temperatures between 0.5° and -2°C. Depending on the climate and cultivars, pots can be marketed year-round.

Transport advice

Temperature	-1,5°C.
Relative humidity	90% to 95%
Fresh air ventilation	Closed
Max. storage life	360 days
Ethylene production	Very low
Ethylene sensitivity	High

Storage disease(s)
The root rot complex, comprised of a combination of Fusarium, Pythium and Rhizoctonia, is the major disease problem during forcing. It causes several problems including a general loss of quality, stunted growth, and prematurely yellowed and senesced basal leaves. In addition, tolerance to Penicillium is needed.

Gladioli

Postharvest storage and transport requirements
After being harvested, cleaned, and then graded, corms and cormlets are initially given 2 to 3 weeks at 15° to 23°C followed by 2°C under highly ventilated conditions for a minimum of 8 to 10 weeks. The latter is required to break the rest period (dormancy) of the corms and cormlets. Corms for commercial uses should be transported at 2° to 5°C under highly ventilated conditions. With the exception of a hot water treatment, unplanted corms are never stored below 0,5°C or above 30°C. Prior to planting, they are given 4 to 8 weeks at 20° to 30°C to promote sprouting. Corms used for very long storage and, thus, very late flowering must be stored at 2°C until planted.

Cut flower production in the greenhouse border soil
During periods of low outside temperatures but where there is sufficient light for the gladiolus’ flower-initiation period, corms can be grown in a greenhouse at 12° to 17°C. Depending on the cultivar and greenhouse temperature, harvesting is achieved in 60 to 120 days. Corms can be delivered year-round.

Cut flower production in the field
During periods when outside temperatures do not get below 10°C but where there is sufficient light during the gladiolus’ flower-initiation period, the corms can be planted outside in the field. Depending on the cultivar and temperature, harvesting can be done in 60 to 120 days. Corms can be delivered year-round. Depending on the climate and cultivar, year-round flowering is possible.

Transport advice

Temperature	0°C to 7°C.
Relative humidity	75% to 80%
Fresh air ventilation	25 or 90 cbm/hr
Max. storage life	150 to 240 days
Ethylene production	Very low
Ethylene sensitivity	High

Storage disease(s)
To control Fusarium, cormlets are stored at 20° to 25°C for 8 to12 weeks, then soaked in running water for 1 to 2 days at 20°C and then given a hot water treatment for approx. 0,5 hour.

Iris

General aspects
Generally, bulbs for very early forcing are stored at 30°C for a few days after being harvested. This is necessary for bulb drying, cleaning and grading. They are subsequently exposed to 500 ppm ethylene for 24 hrs. This treatment stimulates flower initiation, especially with small sized bulbs of some cultivars and bulbs not receiving sufficient heat in the field prior to being harvested. Bulbs for late and retarded (up to one year) forcing are placed at 30°C to suppress their growth and development. Prior to planting they are ‘pre-cooled’ at 5° to 9°C for 6 to 11 weeks, depending on the cultivar. After being pre-cooled, bulbs should be planted as quickly as possible and, if transported, the period should be as short as possible.

Cut flower production in the greenhouse border soil
Depending on bulb size and cultivar, bulbs can be planted in the border soil year-round provided that the soil temperature does not rise above 20°C and that the average greenhouse temperature does not rise above 25°C. The ideal greenhouse temperature is 15°C; a temperature of 18°C can be maintained during the first 3 weeks. This reduces the growing period. Depending on the cultivar and greenhouse temperature, harvesting takes place after 50 to 90 days. Depending on the climate and cultivar, year-round flowering is possible.

Cut flower production in the field
Depending on the climate and bulb size, bulbs can be planted outside in the field year-round provided that the soil temperature does not rise above 20°C and that the average temperature does not rise above 25°C. The ideal temperature is 15° to 17°C. Depending on the cultivar and the climate, harvesting takes place after 50 to 90 days.

Transport advice

Temperature	20°C to 25°C.
Relative humidity	65% to 75%
Fresh air ventilation	90 cbm/hr
Max. storage life	120 to 360 days
Ethylene production	Very low
Ethylene sensitivity	High

Storage disease(s)
The two major storage diseases of Dutch Irises are Fusarium and Penicillium. To assist in controlling these diseases, it is essential to always handle the bulbs carefully to minimize mechanical damage, which provide sites for disease development. Pre-storage and pre-plant fungicidal dips are generally used for Dutch Iris.

Zantedeschia

General aspects
It is generally found that there is a 6-8 week rest period following harvest before sprouting will occur naturally, but the longer the storage period the shorter time to sprouting is required regardless of temperature. Storage of the tuber can be undertaken in temperatures as low as 8°C. However, a transport temperature of approx. 13°C is mostly required with low relative humidity and a fresh air supply of 30 cbm/hr.

Producing Zantedeschia flowers in greenhouse soil and outside in the field
In temperate regions (in the Northern Hemisphere) Zantedeschia can be forced into flower in the greenhouse from 1 April to 1 December and can bloom outside from 1 July to 1 October. In subtropical climates, a combination of greenhouse and field production can be used to realise year-round flowering. In either region, and depending on the cultivars being produced, shading to reduce light intensity by 30% will be needed during the warm period to encourage stretching. In the greenhouse, soil temperatures of 15°-18°C and greenhouse temperatures of at least 15°-16°C. should be maintained. Depending on light intensity, the greenhouse temperature can be allowed to reach 20°C but no higher than 25°C. Soil temperatures, however, may never exceed 20°C due to the risk of damage caused by Erwinia. The production period (planting to flowering) in the greenhouse lasts 80-120 days (this range depending on the cultivar) for a spring planting. For field production in the summer, this will be 40-70 days. And for autumn greenhouse production, this will be 60-80 days. Whether year-round planting in greenhouses and outside is possible depends on the local climate conditions and the cultivar selected. In temperate regions (Northern Hemisphere), Zantedeschia can be planted in greenhouses from December to September and planted in the field from late April to mid-July. In subtropical climates, combining greenhouses and field production allows year-round planting.

Zantedeschia as pot plants
When producing Zantedeschia as pot plants, short cultivars are usually used. These are planted from December – August and grown in the greenhouse at a temperature of approx. 16˚C. Depending on light intensity, the temperature can be increased to 20˚C but no higher than 25˚C. Shading will be necessary under conditions of high light intensity. When the plants reach a height of 2-4 cm., a growth regulator is applied. These pot plants will be saleable after 9 to 12 weeks, the exact length of time depending on the cultivar.

Storage disease(s)
The major diseases affecting Zantedeschia are Alternaria species, Bacterial soft rot, Penicillium (considered more unsightly than detrimental to growth) and Phytophthora. However, generally Zantedeschia are remarkably tolerant to most diseases.

Flowering bulb diseases

The term bulb is used in a general way to describe any plant with a swollen storage system. This includes true bulbs (for example, daffodils, tulips and lilies), corms (which include crocuses and gladioli), tubers (begonias, anemones and cyclamens), and rhizomes for example some irises and trilliums). If one starts with healthy bulbs, bulb diseases are generally not a problem.

Most diseases that can affect bulbs do not generally become a problem, if one starts with healthy bulbs and plant them in sterilized soil. Some of the common problems that may occur include several types of bulb rots, viruses and nematodes.

There are various disease-causing fungi that live in the soil, which can cause bulbs to rot. Plants that are affected may be stunted and have yellow leaves. In some cases plants may fail to emerge. A whitish growth may be visible on the underground shoots and bulbs.

These diseases occur mainly under cool, moist weather conditions and in soggy soils. Remove and discard infected plant material.

Bacterial rot, or soft rot, may begin as a slow yellowing of the leaves often beginning at the leaf tips. Leaves may wilt, collapse and die. Bulbs and the base of the leaves decay and often have a foul-smelling odour. Soft rot is most serious in wet, heavy soils. Provide adequate drainage, and remove infected plants.

Viruses can infect plants, causing leaves or flowers to be mottled or discoloured and growth to be distorted. Control aphids and other sucking insects, which can spread viruses. Dig up and destroy infected plants.

Most common bulb diseases

Symptoms	Small, yellowish spots on leaves; shoots twisted; bulb has dark-coloured scales with yellowish pockets that contain microscopic worms.
Causes	Stem and bulb nematode (Ditylenchus dipsaci)
Plants affected	Narcissus
Prevention and treatment	Dig infected bulbs, along with the layer of soil surrounding the bulbs and destroy. Treat infected soil by solarisation (remove all the plants, till, and cover the bare soil surface with clear plastic for a month to six weeks) or avoid planting bulbs in infected soil.
Symptoms	Bulbs rot, pink or white mould is visible; leaves are stunted, yellow and die.
Causes	Basal rot (Fusarium oxysporum)
Plants affected	Narcissus
Prevention and treatment	Basal rot is common on bulbs planted in locations with soggy soils. When digging and replanting bulbs, check each for disease and discard any with spots or soft areas. Spray plants with a systemic fungicide.
Symptoms	Water-soaked lesions on leaves.
Causes	Anthracnose (Gloeosporium spp.; Colletotrichum spp.)
Plants affected	Anemone
Prevention and treatment	Remove infected bulbs and treat infected soil.
Symptoms	Leaves or flowers are mottled or discoloured; growth distorted.
Causes	various viruses
Plants affected	Gladiolus, Lily and Tulip
Prevention and treatment	Viral infections usually strike plants that are weakened by poor environmental conditions. Control aphids and other sucking insects, which can spread viruses. Dig and destroy infected plants.
Symptoms	slow yellowing and death of leaves stating at leaf tips, wilt and collapse, foul smelling decay of bulbs, leaf sheets and leaf bases.
Causes	Erwinia carotovora (soft rot)
Prevention and treatment	Soft rot is most serious in older plantings and in wet, heavy soils. The bacterium is favoured by warm, wet weather. Provide adequate drainage, remove infected plants and treat infected soil.
Symptoms	Leaves turn yellow; plants are stunted and die prematurely; soft fibrous rot of bulb, somewhat of a dry rot.
Causes	Sclerotium rolfsii (Crown rot or Southern Blight)
Plants affected	Iris, Narcissus, Gladiolus, Tulips and Amarylis
Prevention and treatment	Destroy infected plant materials and fumigate the soil.
Symptoms	Leaves fail to emerge or emerge, turn yellow, wilt and die; underground shoots and bulbs are covered with white mycelium; top of bulbs are infected first, then bulb decay (softy black spots).
Causes	Sclerotinia bulborum (black slime or black rot)
Plants affected	Crocus, Fritillary, Hyacinth and Scilla.
Prevention and treatment	This is a cool, moist weather problem. Destroy infected plant materials and treat infected soil.