Summer may be over, but that doesn’t mean you have to let cabin fever bring you down. While there may no longer be flowers blooming outdoors, October is a great time to begin preparing your favorite spring bulbs for winter flowering indoors. Imagine pots of colorful, fragrant spring flowers (tulips, hyacinths, daffodils, crocuses) on your windowsill in February.
Given the proper treatment, spring bulbs can be “forced,” or induced into blooming indoors, well ahead of their natural schedule and completely outside of their natural environment. Commercial growers in North America force millions of bulbs annually. They will often order their bulbs from suppliers in the United States and in Holland a full year before offering bulb pots to customers in stores. And, since some bulbs bloom more quickly than others, they will often combine several types of bulbs in one container, which allows for a prolonged and changing show of color.
Cornell University is home to the Flower Bulb Research Program, which has been quintessential in developing techniques for forcing flower bulbs into readiness just in time for the holidays and other market opportunities. Research for the program is substantially supported by the Dutch flower bulb export industry, as well as U.S. companies and foundations.
Home gardeners can easily force spring-blooming bulbs, too. Start by selecting quality bulbs and potting them in clean, sterile pots. Use high-quality potting mix or prepare a potting soil that includes garden loam, peat moss and sand. You may opt to add perlite or vermiculite, and maybe bone meal as well. The objective is to find a balance between good drainage and sufficient moisture retention. Bulbs store their own food, so fertilization and feeding are non-issues.
Handle bulbs carefully at all times. Plant them so that they are close together, but not overcrowded. When planting tulips, keep in mind that the largest leaf will always emerge and grow on the flat side of the bulb, so placing the flat side toward the outer edge of the pot will allow the leaf to attractively drape itself over the side of the pot. Don’t twist bulbs into the soil or bury them completely. Leave the ‘noses’ of the bulbs exposed. Once the bulbs are planted, saturate the soil immediately and, thereafter, do not allow the soil to become dry or to freeze.
The next step is to put the planted bulbs into cold storage. Almost all spring-flowering bulbs require a period of cold dormancy before they will begin to grow and bloom. Eight weeks is often adequate, but 12 or more may be required before forcing is possible. Bulbs that have been chilled prior to planting will not require nearly as much cold storage time after planting. Store the planted bulbs in a refrigerator or any other suitable location where the temperature does not drop below freezing or go above 50 degrees F. The planted bulbs must be kept in darkness. If the area is not dark, cover the pots with cardboard boxes, brown paper bags or dark-colored plastic bags with air holes.
Check occasionally to see if roots are developing. You may see roots growing out of the drainage holes in the bottom of a pot or notice vegetative growth from the top of a bulb. If not, a very gentle tug may let you know if a root mass has developed. Once there is enough development for forcing, move the pots into a cool area with bright, indirect light. The cooler the better. Water the bulbs frequently, keeping the soil moist, but not soggy.
In a few days to perhaps two weeks, place the pots in a cool, sunny location. Excessive heat will cause the flowers to open and fade quickly. Cooler conditions will prolong the life of your blooms. Turning the pots regularly and frequently will promote symmetrical growth.
Be creative. For example, place the planted pot in a basket and add moss to cover the pot or ivy to grow out over the basket. Either will make a beautiful gift or centerpiece.
Once your blooms have finished flowering, cut the stems but keep the foliage growing until it begins to wither and die. Don’t pull the leaves off. Store the bulbs in the pots in a cool, dry location until late summer or early fall, at which time they can be planted outdoors. Once forced, bulbs cannot be forced again, but there is a good chance that they will, in time, return to a natural schedule and show flowers, although it may be several years until bulbs that have been forced produce in a garden setting.
If you are unsuccessful the first time, don’t give up. With a little bit of practice, you can master it and enjoy the beauty and fragrance of spring flowers all winter long.
Richard L. Gast, extension program educator II, Horticulture, Natural Resources, Energy, Agriculture programs assistant, Cornell Cooperative Extension of Franklin County, 355 West Main St., Suite 150, Malone, 12953. Call 483-7403, fax 483-6214 or email firstname.lastname@example.org.