How to Force Bulbs Indoors
Many bulbs can be forced or stimulated to bloom indoors. Amaryllis, crocus, hyacinth, narcissus (daffodils and paperwhites), tulips, grape hyacinth and others can be successfully forced to bloom out of season. Look for bulbs that are top quality or have been specifically bred for forcing.
Start with a clean clay, ceramic or plastic container. Use any good-quality potting soil or mix. Place approximately two to three inches of potting soil in the bottom of the container. Place bulbs lightly on the potting soil. Cover the planted bulbs with potting soil, but leave the tips of the bulbs exposed. Water containers until soil is moistened.
After planting, bulbs should be given a cold temperature treatment of 35-38 degrees Fahrenheit for 12 to 16 weeks. An unheated basement, crawl space or a refrigerator or outdoor cold frame which can maintain the cool temperatures are ideal for chilling the bulbs. The amount of chilling required varies with type of bulb and cultivar, and bulb size. Your local supplier can provide information about the specific cultivar chosen. After chilling, the bulbs will need 2-3 weeks at room temperature before growth starts.
After bringing the bulb containers in from chilling, place the pots in indirect sunlight at 60-65 degrees Fahrenheit for several weeks. As the new shoots turn green, expose to increasing amounts of light to stimulate flowering. Flower buds usually appear within 3-4 weeks. Make sure to keep the soil moist as the bulb blooms. Bloom time can be extended by moving plants into a cool area at night.
Some bulbs, such as paperwhite narcissus and amaryllis can be forced without chilling treatment. Guidelines for planting these bulbs are in the following Planttalk scripts:
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Updated Wednesday, October 12, 2016