Forcing Bulbs Indoors

Step 1: Select Bulbs

The first thing to consider is where and what kind of bulbs to purchase. It's best to by from a reputable company and to stick with cultivars that are recommended for forcing. Handle your bulbs with care, dropping or subjecting them to extreme temperatures will hurt them and your chances of a bloom. If you cannot plant your bulbs right away store them in a cool place with temperatures between 35 and 55 degrees. Store them in a mesh or paper bag (with holes) to permit ventilation.  Remember some bulbs are poisonous and shouldn't be stored in the fridge with your food.

The potting medium must be well drained, retain adequate moisture and be able to anchor your bulbs. Commercial potting soil is adequate, but a better choice is a mix of equal parts potting soil, sphagnum peat moss and perlite. Since the bulbs already contain enough food for the developing flowers and roots, they do not require fertilizer. Use clean pots that have drainage holes in the bottom. If you use clay pots, soak them overnight so they won't draw moisture from the planting medium. Gulley Greenhouse potting mix is a good choice for use.

After setting the bulbs, fill the pot with soil to within ½ inch of the rim. Add water until it drips through the drainage holes in the bottom of the pot. Label each pot, noting the name of the cultivar, the planting date and the date to be brought indoors for forcing.

Step 3: Cooling

All hardy bulbs must be exposed to cool temperatures between 35 and 50 ºF to prepare them for subsequent leaf and flower growth. During this cool period, the plant's roots are forming and the stem is elongating. The optimum cooling period is from 12 to 16 weeks. They can be cooled anywhere from 12 to 18 weeks but the stem length will suffer. If the bulbs were held in the refrigerator for more than three weeks, subtract three weeks from the required cooling time.

 Any structure that maintains temperatures between 35 and 50 ºF is fine (e.g., an unheated basement, crawl space, or an old refrigerator). You can put the potted bulbs in a cardboard box with leaves and store in your garage. Or dig a trench outside, put in your pots, fill in with soil, and put a couple inches of straw on top. Water regularly.

Step 4: Forcing

After the cooling time is over, take your pots out and give them warmth and light. This triggers the formation of leaves and flowers. Choose a cool location (60 to 65 ºF) that receives indirect sunlight. When the shoots turn green, expose the pots to warmer temperatures and more light to stimulate growth and flowering. Rotate the pots regularly so that all the leaves receive an equal amount of light.

Flower buds can be expected within three to four weeks. When the buds begin to show their color, move the pots out of direct sunlight to prolong the flowers. Be sure to keep the soil evenly moist throughout the forcing period. Flowers will last longer if the pots are moved into a cool room at night

Hardy bulbs that have been forced to flower should be planted in the garden once spring arrives, or allowed to mature and go dormant in their pots and planted in the fall. Daffodils can be transplanted into the garden in the spring. They will not flower the following year, but may the year after. Other bulbs such as tulips and hyacinths are best discarded after forcing.

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