October is the time of year to begin potting your favorite spring bulbs to prepare them for winter flowering. I usually forget to talk about forcing bulbs in the fall and only remember in December or January, when I am anxious for some sunny flower color. If you forget to start your forcing now, you are relegated to use bulbs like paperwhites and Soleil d’Or, daffodils that do not need a cold treatment. However, this year I remembered! So, you can buy tulips, any type of daffodil, hyacinths, crocus, scilla, grape hyacinths or any other bulb sold for fall planting and spring bloom. Most garden centers are carrying those bulbs for outdoor planting, but you can also force them to bloom early indoors and bring some color to your winter windowsill.
Begin by potting the bulbs in clean, sterile clay or plastic pots. Do not bury the bulbs; leave the “noses” of the bulbs exposed. The soil should be a mixture of good garden loam (three parts), peat moss (two parts), and sand (one part). You can also use a commercial soil-less mix, but be careful the medium doesn’t stay too wet. Don’t worry about soil fertility or feeding bulbs because they have enough stored food to flower one time.
Plant the bulbs close together in the pot. Usually 6 tulip bulbs, 3 hyacinths, 6 daffodils, or 15 crocus, will fit into a 6-inch pot. Place the flat side of the tulip bulb next to the rim of the pot since the largest leaf will always emerge and grow on that side, producing a more desirable looking pot. Fill the pot loosely with soil. Don’t press the bulbs into the soil. Allow 1/4-inch of space at the top of the pot so it can be watered easily. Water immediately upon planting, and never allow the soil to become dry.
Bulbs require a cold temperature treatment of 35– 48 degrees F for about 12–13 weeks, but this varies by bulb (see chart below). This cold treatment can be provided by either in a cold frame, an unheated attic or cellar, or even your refrigerator’s vegetable section. In the refrigerator, the pots should be covered with plastic bags that have had a few breathing holes punched in them. With cold frames, cover pots with deep mulch for insulation. Do not allow the bulbs to freeze.
|Bulb||Chill time||Time to bloom after chilling|
|Crocus||8-15 weeks||2-3 weeks|
|Daffodil||2-3 weeks||2-3 weeks|
|Grape hyacinth||8-15 weeks||2-3 weeks|
|Hyacinth||12-15 weeks||2-3 weeks|
|Iris||13-15 weeks||2-3 weeks|
|Paperwhite daffodil||None||3-5 weeks|
|Snowdrops||15 weeks||2 weeks|
|Tulip||10-16 weeks||2-3 weeks|
When you bring bulbs indoors, a temperature of 50–60 degrees F is preferred for the first week or until the shoots and leaves begin to expand. Then, they can be moved to warmer locations such as the living room. Avoid direct sunlight. Once the bulbs are blooming, move the pots to a cool location each night. The cooler temperatures will prolong the life of the flowers. Small pots of crocus can even be placed in your refrigerator overnight. Discard tulips, narcissus, crocus, and hyacinths after flowering as they normally are “spent” and are not likely to ever flower satisfactorily again.
Hyacinths, crocus, and narcissus also can be forced in water. Special clear, glass vases are made for hyacinths or crocus. Place the bulb in the upper portion, water in the lower portion. Keep the vase in a cool, dark room (preferably under 50 degrees F) for four to eight weeks until the root system has developed and the top elongates. At this point place it in a bright window, where the plant soon will blossom.