Forcing is the process of stimulating plants to bloom out of season. You can plant bulbs in pots during October or November to bloom from January through April.
You can force many popular flowering bulbs indoors, including daffodils, tulips, hyacinths, and crocuses. Most of these take 10 to 20 weeks from planting to bloom. Paperwhite narcissus take only 6 to 8 weeks to bloom, however, so they are the best choice if you want flowers sometime around the holidays.
The key to success lies in the timing of each step in the forcing process. Here's a simplified outline of the process:
1. Select clean pots with drainage holes in the bottom. The pot should be at least twice as deep as the bulbs to allow good root development, though it's best to use a broad, shallow pot that won't tip over when the plants get top-heavy after blooming.
2. Fill each pot loosely with a lightweight potting medium, leaving space for the bulbs to sit in the soil with their tips just below the pot rim. Do not compress the soil or press the bulbs into it. Cover the bulbs with potting mix up to the rim of the pot, then water. Watering compresses the potting mix enough to leave space for future watering.
3. Put pots of bulbs in a cool, dark place to prepare them for later leaf and flower growth. You can use any structure — such as a root cellar, an unheated basement, an old refrigerator — where you can keep the temperature between 35 and 50 degrees F.
4. To force the blooms, bring the pots out of the cool environment into warmth and light to trigger the formation of leaves and flowers. For best results, give the bulbs a temperature of 60 degrees F and direct sunlight. From the time you remove them from storage, the bulbs require another three or four weeks to bloom. If you have prepared a number of pots for forcing, you can bring out one per week to provide a longer period of blooms.
5. Rotate the pots regularly so that all the leaves receive an equal amount of sunlight. To prolong the bloom, remove the plants from direct sunlight when they begin to flower. Keep the soil moist throughout the forcing period.
Note that paperwhite narcissus are best kept in a cool, but not so cold, spot (50° to 60°) in low light until they are well-rooted and shoots appear — usually in two to three weeks — before placing them in sunlight.
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