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Cornell University : Cornell Cooperative Extension
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| Yates Association |
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Forcing Bulbs for Indoor Bloom |
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If you desire to force spring flowering bulbs, it is necessary to provide a low temperature treatment to the bulbs to promote flowering. After purchasing bulbs, store them in a cool (55-65 degrees F.), dry area (basement, cellar, garage). Temperatures above 65 degrees F., and below 50 degrees F. should be avoided. Crocus, daffodils, hyacinths, narcissus and tulip bulbs are some of the easiest bulbs to force. Forcing consists of two phases. First, the bulbs develop roots and buds, and second, the bulbs bloom. Cold treatment ranging from 35-48 degrees F., preferably 40 degrees F., is required. Cold treatment can be provided in a refrigerator, in a cold-frame, or in an unheated cellar or basement. The bulbs must be given the cold treatment for a minimum of 12 to 14 weeks. Bulbs can be planted any time between October 1 and December 1. As a general rule, plant early for early flowering and late for late flowering, always allowing 12 to 14 weeks for the cold treatment and 3 to 4 weeks for flowering. Only clean pots with adequate drainage holes should be used. The clean pots should be loosely filled with a good, well-drained soil mix so that the top of the bulb will be even with the top of the pot. Vermiculite may be used instead of the soil mix. The soil should not be packed. Loose soil favors more rapid rooting. Tulip bulbs will have a flat side; plant this bulb so that the flat side is toward the outside of the pot. Cover the bulbs with the same soil mix used for filling the pot, never pressing them into the soil. Fill the pot to within 1/4" of the top so that the bulbs can be easily watered. Label each pot with the name of the cultivar, the date of planting, and the date to be carried in the house. The second phase of forcing begins after 12 to 14 weeks of cold treatment. At this time, bring the plants into a cool (60 degrees F.), well-lighted area in the house. Water the plants daily. If possible, avoid severe drafts. The major point is to avoid extreme heat. After the flowers have faded, remove the flowers only. Keep the plants watered until the foliage dies. Then, store the bulbs for replanting in the garden in the fall. Cornell
Cooperative Extension Yates Association |
