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The secret to forcing bulbs is to plant them early enough to allow plenty of time for strong roots to develop, making sure the temperature stays cool during that time. Most spring-blooming bulbs need 12 to 16 weeks of 45-degree (7C) temperatures after they are potted to develop roots strong enough to support leaves and flowers.
There are a few methods to keep bulbs cool. One way is to keep them in an unheated basement or crawlspace. The pots need no light for this process. You can also bury the pots in a trench or hole. Dig a hole deep enough to submerge pot completely and provide drainage. Cover pot with lightweight material such as sawdust, hay or fir bark.
Bulbs for forcing are planted shallower than normal. Place them just below the soil surface, water them thoroughly, and then place them in a cool spot for root development. Periodically inspect pots for root development. If roots have emerged from the pot bottom, it is ready to be brought out to warmer temps and more light. Place pot in bright shade, away from direct sun. After shoots are green, begin gradual exposure to the sun.
To force bulbs in water is similar. Unfortunately, fewer types of bulbs respond to this treatment. Hyacinthus orientalis varieties and some Narcissus groups (Jonquil, Poetaz, and Polyanthus) are best. Try to choose the largest bulbs available.
Suspend the bulb's rooting end just above the water. Do not let the bulb touch the water for a prolonged amount of time as this could cause rotting. The roots will grow down into the water in a cool, dark place over the succeeding 12 to 16 weeks. When a good root system has developed, begin the gradual exposure to light.
Forcing bulbs in gravel is done the same way. Sink the bulb halfway into the gravel and add water to just below the bulb as before. Water level may be difficult to judge through the gravel, but you can dig a small hole or well next to the bulb to estimate. Root in the dark and then adapt slowly to light as in the previous methods.