Forcing bulbs is a popular way of stimulating them to bloom out of season. Among the most commonly forced bulb flowers are amaryllis, paperwhite narcissus and hyacinths. Although there are specially-designed containers for bulbs such as hyacinths and paperwhites, almost any container will suffice. The best soil mix for forcing bulbs should contain equal parts soil, peat moss and perlite or vermiculite. Common potting soil can be too moist and can cause root rot.
When planting the bulbs, fill the container three quarters full with mixed soil and place the bulbs close together. After this is completed, fill the surrounding areas of the container with soil, leaving just the tops of the bulbs visible. The bulbs should then be watered in.
All spring bulbs, with the exception of paperwhites, require a period of cold of at least 3 months to initiate bloom. This can be achieved in a variety of ways. Bulbs can be stored in an unheated garage or basement or even a refrigerator. During this time, the soil should be kept slightly moist and it’s best advised to periodically check it for moisture retention. When the cold period is over, bring the bulbs out to a warm sunny location. Water and fertilize with a liquid bloom booster. They will require more water now that they are growing.
Following are examples of how many weeks of cold are required for certain types of bulbs:
Crocus - 15 weeks of cold
Daffodil - 15
Hyacinth - 11-14
Iris - 15
Paperwhite Narcissus - none
Tulip - 15-17