Forcing Bulbs Indoors Provides a Harbinger of Spring
After the excitement of the holidays fade, we turn reluctantly to the long, dark, cold days of January and wish for the joyful color of early spring blooms. What could brighten our homes as we await warmer weather and more sunlight? One answer would be to force some bulbs to burst into bloom indoors!
The Magic of Bulbs
Bulbs are neat little plant packages that include food storage tissue to sustain the plant during its life cycle. They are designed to withstand cold winter temperatures. The cold triggers the biochemical process necessary to break down the bulb’s store of starches and carbohydrates and turn them into glucose, the primary energy the bulb uses to grow roots and flower.
Bulbs for Forcing Indoors
Selecting the right bulbs for indoor forcing is the key to success. Most bulbs require an extended cooling period of 10 to 15 weeks. After cooling, bulbs placed in a warm location (60-65 F) need a number of weeks (from 2-3 to 5-6) to form leaves and bloom. This is true whether you plant bulbs outside or force them inside. The time to plant spring blooming bulbs outside in Central Virginia (September through November) is clearly long past.
Starting the cooling in mid-January or later for indoor forcing could mean that your bulbs bloom indoors about the same time bulbs are starting to bloom outdoors. And that is too long to wait for spring cheer in the midst of winter!
Fortunately, there are some bulbs that just require a minimum amount of cooling in your house (Paper White Narcissus) or no cooling time at all (Amaryllis). Forcing these bulbs indoors is an easy way to enjoy spring blooms inside in the late winter and early spring.
Look for large, firm, and unblemished bulbs online or at your favorite gardening store or nursery.
Planting a large number of Paper Whites (Narcissus species) in a container will provide an abundant cluster of small white, yellow, or orange flowers on 12- to 18-inch-tall stems. Choose the Paper White Narcissus, the yellow cultivar Soleil d’Or or the white and yellow-cupped Chinese Sacred Lily (Narcissus tazetta orientalis) for easy forcing, or experiment with other varieties. Remember that the fragrance of Paper Whites is strong and may not be agreeable to some people.
Plan on placing a single Amaryllis bulb (Hippeastrum species and its hybrids) in a pot for forcing, either purchased loose or in a kit with a pot and potting medium. Amaryllis bulbs often produce two stalks with two to six flowers per stalk. Options include single-, double-flowering or miniature varieties in many colors (red, pink, orange, salmon, white or bicolor).
For Paper White Narcissus:
- Put 2-3 inches of pebbles, pea gravel, sand, or pearl chips in a shallow pan or bowl, with no drainage hole. The top of gravel should be one inch below the top of the container. Add water to just below the gravel surface.
- Place the bulbs so the bottom quarter of the bulb is covered in gravel and maintain the same water level to prevent bulbs from rotting.
- Keep the bulbs in a cool location (50-60F) in low light until well rooted, usually 2-3 weeks. The location can be a corner of the refrigerator, a cool basement, or an unheated garage.
- Then bring them gradually into direct sunlight and warmer temperatures.
- Discard the bulbs after bloom since they are not likely to re-bloom next year.
- Another option is to plant the bulbs directly in a pot with soil.
- Plant in light rich soil in a pot 1-2 inches larger in diameter than the bulb, with the upper half of the bulb exposed.
- Use a soilless sterile mix available at garden centers that includes 60-70% sphagnum peat moss, 10-30% perlite and 0-20% horticultural grade vermiculite, or make your own.
- Water thoroughly, usually once a week, but allow soil to become dry between waterings.
- Place in a warm, sunny area until the flower buds show color, then move it to a location with indirect sunlight.
- After the first leaves appear, rotate the pot periodically to keep the stems straight.
- Put the pot in the coolest part of your home every night to help keep the blooms longer.
- With proper care, bulbs can be saved and forced to flower the next year.
More Blooms to Explore
Once you have experimented with indoor bulb forcing, you may want to explore some other easy spring flower bulbs like hyacinths, Muscari and large flowering crocus, or try those that require a bit more attention, like tulips, miniature daffodils, lily-of –the-valley and freesias.
On-line bulb catalogues also provide the opportunity to buy pre-chilled bulbs that can be grown indoors or in warm climates that do not provide the cold temperatures they need. Check the package for planting instructions or refer to the references below.
Your experience with growing bulbs indoors this winter may just inspire you to mark your calendar with a reminder to buy bulbs early enough in the late summer to plant them both outside AND experiment with more indoor bulb forcing indoors!
“10 Spring Bulb Questions,” P. Allen Smith, P. Allen Smith Garden Home, December 2015.
“Amaryllis,” Nancy Doubrava & Bob Polomski, Clemson Cooperative Extension, Home & Garden Information Center, Factsheet HGIC 1551, 1999.
“How do you force paperwhite narcissus?,” Iowa State University, Extension & Outreach, Horticulture & Home Pest News.
“Forcing Bulbs for Indoor Bloom,” Revised by David H. Trinklein, University of Missouri, UM Extension, Revised June 2010.
“Questions About Bulbs,” The Netherlands Bulb Council, Texas A&M University, Texas Cooperative Extension, Horticulture Update, January-February 2005.
“Fooling Mother Nature: Forcing Flower Bulbs for Indoor Bloom,” George Graine & Holly Scoggins, Virginia Cooperative Extension, Publication HORT-76NP, 2014.
“Forcing Bulbs,” Carol Matheson, Penn State Extension, Penn State Master Gardener, September/October Newsline, 2011.
“Forcing Bulbs,” Ann Joy & Brian Hudelson, University of Wisconsin-Madison, Wisconsin Horticulture, Division of Extension, Revised 2012.
“Forcing Bulbs Indoors,” Bob Polomski & Al Pertuit, Revised by Barbara H. Smith, Clemson Cooperative Extension, Home & Garden Information Center, Factsheet HGIC 1556, Revised 2016.