Many fall planted, spring flowering bulbs may be grown indoors to bloom during winter.
Some of the most commonly indoor forced bulbs are small early tulip varieties, crocuses, daffodils, narcissus, and hyacinths. Pot these bulbs in a well-drained planting mix and containers with drainage holes. Plant the bulbs so that they are only half covered with potting soil. Allow for 2.5 cm (1 in.) or more of soil below the bulbs. For best results plant bulbs with time same flowering in same container.
Most hardy outdoor bulbs require a cool dormancy period at 3-10 C (35-50F) after they are potted. A cold room or an extra refrigerator can be put into use for this purpose. However, apples or cabbages must not be in the same area since they release ethylene gas which will damage flower buds. These bulbs require total darkness during dormancy; be sure to cover the bulb pots if they are located in an unheated porch or daylight-exposed area.
The length the cool period varies depending on the type and variety of bulb. The cooling requirements for some of the popular forcing bulbs have been listed below to help you with choosing compatible bulbs.
During the cool period keep the soil barely moist; check every week or so to make sure the soil does not dry out. If the bulbs are kept too wet the they can rot; dust bulbs with Bulb Dust before planting or soak them in a Benomyl solution to prevent such problems. Benomyl also controls the growth of mould on the soil surface.
Once bulbs show signs of shoot development move them into a warmer, 15 C (60 F), brightly lit location and keep the soil evenly moist. Warmer temperatures may damage the flowers. After the buds appear the pots may be moved into any light for display. After blooming bulbs can be discarded (they cannot be forced again) or saved for planting outside later in the spring.
Hyacinths can be forced in special hyacinth glasses which are filled with enough water to touch the base of the bulb. They will still need to be cooled in water-filled glasses for 10-12 weeks.