UC Master Gardeners

Forcing blooms in winter a fun way to fool Mother Nature

November 28, 2012 

Blooming Hyacinth

The elegant hyacinth, pictured at left, can easily be ‘forced’ to bloom for springtime color and fragrance.

COURTESY PHOTO

There may be a time in the upcoming winter that you yearn for spring fragrances and color before their time. Getting spring bulbs to flower indoors in the winter is called “forcing.” It’s fun to “fool Mother Nature,” and potted spring bulbs make great gifts for the upcoming holidays.

Normally a spring bulb is dormant in the winter. Shoot growth begins in the spring when temperatures rise. Flowering follows.

In order to force a bloom, you must mimic its natural pattern and expose it to cold (aka chill time). Bulb varieties differ in their chill or dormancy requirements. A chill temperature is considered to be around 40 degrees, but length of time varies in plant varieties.

Bulbs can be chilled in a bag in a refrigerator before planting or can be chilled in the pots you wish to grow them in. Place planted pots in a cool garage or cellar, or dig a trench in a shady area of your garden and cover with dried leaves, straw, or spagnum moss.

Dig up when ready to place in light and “force” the bloom.

Some bulbs are more easily forced to bloom than others. Both paper white narcissus and amaryllis need no chill time. Other spring bulbs need more chill time.

The elegant hyacinth can be forced in hyacinth vases using only water. It needs 10 to 14 weeks of chill time, then two to three more weeks to bloom. Small flowers such as the Muscari (grape hyacinth) and snowdrop can be clustered in pots. They need 13 to 16 weeks of chill. Siberian squill (Scilla siberica) need 15 weeks of chill as do some tulip varieties.

Once bulbs have completed their chill cycle, expose them to low light until their leaves turn green. Finally, they can be placed in a sunny window where they “go into action.” If you are thinking of giving potted bulbs as holiday gifts, get them started now. Enclose a handwritten card with instructions on how the receiver can finish the process to enjoy spring blooms in the upcoming months.

GOT A GARDENING QUESTION?

Contact the University of California Cooperative Extension Master Gardeners at 781-5939 on Mondays and Thursdays from 1 to 5 p.m. in San Luis Obispo; at 473-7190 from 10 a.m. to noon in Arroyo Grande; or at 434-4105 on Wednesdays from 9 a.m. to noon in Templeton. Visit the UCCE Master Gardeners Web site at http://ucanr.edu/sites/mgslo/ or e-mail mgsanluisobispo@ucdavis.edu  .

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