Choosing bulbs:

Most spring-blooming bulbs can be forced into bloom. The most common choices are hyacinths, tulips, narcissus, grape hyacinths and crocuses. Catalogs and garden center displays often indicate which cultivars and types of bulbs are more suitable for forcing. Choose only top size bulbs for best blooms.

Almost any type of pot can be used for forcing bulbs.  Paperwhite narcissus can be easily forced in a shallow container of water using pebbles for support. More extensive forcing projects are best done in clay or plastic pots that have adequate drainage holes.

Soil mix:

I use Commercial "soil-less" potting mixes. Bulbs for forcing should not be planted in ordinary garden soil or in potting mixes that are labeled "potting soil." Potting soil mixes are often no more than a fine form of peat moss. This type of material holds too much moisture and may cause water-related disease problems.

Planting:

Fill the pots 3/4 with potting mix. Place the bulbs closely together. Spacing the bulbs to planting bulbs in the garden do not apply when the bulbs are to be forced. Place tulip bulbs with the "flat" side facing the edge of the container. After you arrange the bulbs, place additional soil around them. Do not fill the pots to the top with the potting mix. The tops of tulip and narcissus bulbs do not need to be covered. The bulbs should then be watered.

Cold period:

All of the spring-blooming bulbs, with the exception of paperwhite narcissus, must have a cold period of at least three months to initiate bloom. You can do this cooling  period in a variety of ways. Potted bulbs can be stored in a refrigerator or in an unheated garage or cellar, or outside as if they are in the ground if you are in a cool climate that freezes at night. Pots in a refrigerator tend to dry out rapidly; check periodically to ensure that the soil is moist.

Here is a list of how long each type of bulb need to be cooled inorder to cause them to bloom.

Common Name                          Weeks of Cold

Crocus      15
Daffodil     15
Glory of the snow    15
Grape Hyacinth     14-15
Hyacinth     11-14
Iris 15
Iris reticulata none
Iris danfordiae    14-20
Paperwhite narcissus none
Tulip      15-17

Forcing:

After bulbs have been chilled, bring the pots inside for blooming. Check the pots to see if the bulbs have produced an adequate root system (look to see if any roots are visible through the drainage holes). The number of weeks it takes before the plants actually bloom depends on the environmental factors in the home, but the average is two to three weeks.

Water the pots thoroughly when bringing them inside. Place pots in a cool area of the home (high light intensity is not important at this point) and leave pots in a cool location until active growth is visible. Take care not to over-water. Once active growth begins, you can move the pots to a warmer location that receives more light. Forcing bulbs slowly is more desirable than placing them directly in a bright, warm location. The quick transition from chilling to warm temperatures can sometimes "blast" the buds, which means everything moves too fast and the bulbs do not bloom. Because of the warmer indoor temperatures, flowers from bulbs that are forced indoors do not last as long as outdoor flowers. Forcing several containers of bulbs on a staggered schedule extends the indoor display.