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TULIP
Forcing in the greenhouse border soil |
Five-degree tulips
Depending on the
required flowering period and the cultivar, these bulbs receive a
5�C to 2�C cold treatment for 9 to 14 weeks. The bulbs are then
planted in the greenhouse soil where, depending on the greenhouse
temperature, flowers will be harvested in 35 to 60 days (the warmer,
the earlier). The cold treatment is given in the Netherlands before
the bulbs are shipped. If the duration of transport is long,
however, part of this cold treatment can be done during shipping.
These five-degree tulips are usually brought into flower from late
November to early March. |
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Nine-degree (pre-cooled) and non-cooled tulips
Depending on the required flowering period and
cultivar, non-cooled bulbs can receive their cold treatment by
exposing them to ambient temperature in the greenhouse soil for 13
to 20 weeks. If part of the cooling treatment (no longer than 9
weeks) is applied to the dry bulb (i.e. not planted), this is done
in a cold store set at 9�C or possibly 5�C (the 9� setting being
used for pre-cooled tulips). Nine-degree tulips can be brought into
flower from early December to early April. |
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Forcing in boxes or pots |
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Nine-degree (pre-cooled) and non-cooled tulips
Depending on the required flowering period and
cultivar, the bulbs receive, after being planted and standing in the
rooting room, 13 to 20 weeks of cooling. At the beginning of the
cooling period, the temperature is set at 9�C but is gradually
reduced to 0�C (non-cooled bulbs). For pot tulips, the cooling
period is 2 weeks shorter, the cooling treatment being given after
the bulbs have been planted in boxes or pots placed in the rooting
room at the floriculturist�s premises. Part of the cooling treatment
can be applied to the dry bulbs (nine-degree pre-cooled tulips)
before planting them in boxes for completion of the cooling
treatment.
Once the cooling treatment has been completed, the boxes or pots
are taken from the rooting room and placed in the greenhouse. At a
greenhouse temperature of 18 to 20�C, the flowers are marketed in 3
to 4 weeks (the warmer, the earlier). Depending on the greenhouse
temperature and the cultivar, flowers can be produced from December
to April. |
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Forcing in water |
Nine-degree tulips
Depending on the
required flowering period and cultivar, bulbs receive 13 to 20 weeks
of cooling. At the beginning of the cooling period, the temperature
is set at 9�C but is gradually reduced to 0�C. During this last part
of the cooling period (the rooting period), tulips are kept at a
temperature of 5�C. Once the cooling period is completed, the boxes
are taken from the rooting room and placed in the greenhouse. At a
greenhouse temperature of 16 to 18�C, the flowers are harvested in 3
to 4 weeks (the warmer, the earlier). Depending on the greenhouse
temperature and cultivar, flowers are produced from December to
April. |
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Retarding in boxes |
Ice
tulips
These bulbs are planted in boxes in November and
then allowed to root at 9�C or 5�C for 3 to 6 weeks. After this
rooting period, the boxes are frozen, wrapped in plastic and stored
at �1.5 to -2�C. Usually, the boxes are taken into the greenhouse or
put in a cool place outside after the summer months at which time
the tulips are allowed to come into flower. This method is used to
force a limited range of tulips during the autumn months.
Unfortunately, the attractiveness and keeping quality of these
tulips is sometimes less than ideal. This is the reason, therefore,
that this production technique is not discussed here in detail.
Nevertheless, with certain cultivars and the proper treatment, there
are good commercial opportunities for its application. Depending on
the climate and cultivar, flowers can be produced from May to late
November with the exception of warm summer months. |
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