Difference between revisions of "Flower Bulbs"
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+ | <b>Guidelines for storing flower bulbs</b> | ||
+ | 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.<br><br> | ||
+ | <b>General remarks:</b> | ||
+ | * 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<br><br> | ||
+ | <i>No liability whatsoever is accepted for the consequences that result from the use of this information.</i><br><br> | ||
+ | <b>Frost damage</b> | ||
+ | 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.<br><br> | ||
+ | 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. |
Revision as of 14:16, 31 October 2012
Infobox on Flower Bulbs | |
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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
Contents
- 1 Flower Bulbs
- 1.1 Description / Application / Shipment / Storage
- 1.1.1 Bulb production
- 1.1.2 Environmental management
- 1.1.3 Bulb flower production
- 1.1.4 Commercial cultivation techniques
- 1.1.5 Plant breeding
- 1.1.6 Vegetative propagation
- 1.1.7 Propagation by means of tissue culture
- 1.1.8 Favourite spring flowering bulbs
- 1.1.9 Favourite summer flowering bulbs
- 1.1.10 Bulbous and Tuberous groups
- 1.1.11 Storage spring bulbs
- 1.1.12 Storage summer bulbs
- 1.1 Description / Application / Shipment / Storage
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).
![Flower bulbs 1.jpg](/images/8/86/Flower_bulbs_1.jpg)
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.
![Flower bulbs 2.jpg](/images/4/4b/Flower_bulbs_2.jpg)
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.
![Flower bulbs 3.jpg](/images/7/7d/Flower_bulbs_3.jpg)
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.
![Flower bulbs 4.jpg](/images/f/f3/Flower_bulbs_4.jpg)
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.
![Flower bulbs 5.jpg](/images/a/ae/Flower_bulbs_5.jpg)
Caladium
An example of a tuber comprised primarily of enlarged stem tissue. Tuber with six large dominant buds or sprouts.
![Flower bulbs 6.jpg](/images/9/93/Flower_bulbs_6.jpg)
Dahlia
An example of a tuberous root comprised primarily of enlarged root tissue.
![Flower bulbs 7.jpg](/images/b/bd/Flower_bulbs_7.jpg)
Iris Germanica
An example of a rhizome comprised primarily of a specialised horizontal stem.
![Flower bulbs 8.jpg](/images/f/f2/Flower_bulbs_8.jpg)
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) | ry 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.