Forcing Bulbs OH 46
Leonard Perry, Extension Professor
Tulips, hyacinths, daffodils, and crocus offer an array of color that can be
used to create a bright "spring" indoors to
help counteract winter's bleakness. These hardy bulbs can be forced, which means growing them to produce bloom
well out of the plant's normal season of flowering after a period of cold treatment. It is best to use those cultivars
(cultivated varieties) recommended for forcing purposes as listed in the catalogues.
The following steps will help in forcing bulbs successfully.
1.Bulbs can be potted anytime from September 1 to December 1. Schedule potting so as to allow 8 to 12 weeks
of cold treatment before tulips can be forced, and 8 to 10 weeks of cold treatment before hyacinth, daffodil,
and crocus can be forced. For example, pot up tulips around October 1 for blooms in January.
2.Select bulbs that are heavy, solid, and blemish-free. Look for large size, not "bargain bulbs," because these
large bulbs force easier and have larger blooms.
3.Bulb pans are the preferred containers. These are clay or plastic pots that are much wider than high. A drainage
hole is necessary. For water culture, wide, shallow containers with a depth of at least 2 inches may be used.
4.The mechanical condition of the soil used is important--a light, well-aerated mix is necessary to ensure proper
drainage. Mix equal parts (by volume) of potting soil, sphagnum peat moss, and vermiculite or perlite. Fertilizer
is not necessary because the bulb itself contains sufficient food to produce good bloom.
5.Fill the pots with soil mix so that when the bulbs are set on the soil the "neck" of the bulb will be about 1 inch
below the pot rim (so that three-quarters of the bulb will be covered with soil). Set the bulbs close together, but
not touching; plant either five or six tulips, three hyacinth, three daffodil, or six to twelve crocus per 6-inch pot
(depending on bulb size). Once the bulbs are set in the pot, add soil until only the bulb tips are visible. Then
water the bulbs thoroughly; it may be necessary to add more soil as it settles.
6.Mark each pot with a durable, waterproof tag, indicating the kind of bulb and cultivar, date of planting, and date
of removal from cold storage. It's a good idea of protect pots from mice (except for daffodils, which they don't
usually bother) by placing wire screen over the top of the pots.
7.Bulbs (except paper white narcissus) must be exposed to a cold treatment (35 to 40 degrees F) for the number
of weeks indicated in step#1 while roots are forming. Any cold, dark area can serve as a storage area--a cool
cellar, garage, outdoor shed, or cold frame where the pots will not freeze. An old refrigerator could also be
used. Additional watering may be necessary for these pots so check them occasionally.
Pots can also be stored in an outdoor trench, dug 12 to 15 inches deep, and wide and long enough to hold the
pots. Make sure the trench is well drained; gravel or sand can be put in the bottom to improve drainage. Set
pots in the trench and cover with soil to the original ground level. Just before hard freezing, place a 5-inch layer
of straw, leaves, or other organic matter over the area and cover this with evergreen boughs or burlap bags. No
extra watering should be needed.
8.One sure sign that pots are ready to bring in to force is that the bulbs' roots will be growing through the drainage
hole in the pot, and that a good root mass has formed in the pot (it can be easily knocked out of the pot). At
this point, a few pots can be brought in at a time to provide a succession of bloom.
9.Upon bringing a pot of bulbs indoors to force, water well, and expose to cool temperatures (40 to 50 degrees
F) and low light for a week. Then gradually move pots to good sunlight and an area where night temperatures
are about 60 degrees F (flowers will last longer at lower temperatures). Keep pots well watered.
10.When bloom is over, gradually reduce water, but water enough to keep foliage green. Plant bulbs outside as
soon as the soil can be worked to allow foliage to mature. Forced bulbs may not flower the following season
because the forcing process takes so much from the bulbs.
(Adapted from Jane Warner, Ohio State University)
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lawrence Forcier, Director, UVM Extension System, Burlington, Vermont. University of Vermont Extension System and U.S. Department of Agriculture cooperating, offer education and employment to everyone, without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.
Last reviewed 2003