Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
10/11/99
Contacts:
Cindy Haynes, Horticulture Department, (515) 294-4006,
chaynes@iastate.edu
Elaine Edwards, Extension Communication Systems, (515)
294-5168, eedwards@iastate.edu
Yard and Garden Column for the Week Beginning Oct. 15
Fooling Mother Nature - Forcing Flower Bulbs Indoors
By Cindy Haynes
Extension horticulturist
Iowa State University Extension
While we are searching the garden centers for bulbs to plant outdoors this fall, why not pick a few extra bulbs to force indoors this winter. There is nothing quite like enjoying the beauty and fragrance of a hyacinth in March during a snowstorm. But fooling Mother Nature does require a little pre-planning this fall.
When purchasing bulbs for forcing, select only large, firm bulbs that are free from blemishes and pests. The old adage, "the bigger the better," is definitely true in this case. The larger bulbs produce the best floral display. Several types of bulbs can be forced indoors. Tulips, daffodils, hyacinths, crocus, grape hyacinths, paperwhites and amaryllis are a few common types of bulbs that are often forced for winter bloom.
After purchasing the bulbs, select an appropriate container. Clay, plastic or ceramic containers may be used for forcing. Normally a 4- to 8-inch diameter container is used for forcing bulbs. Smaller bulbs like crocus and grape hyacinths can be planted in the smaller containers, while amaryllis bulbs require a 6- to 8-inch diameter pot. The basic requirements for the container are that it be clean and provide adequate drainage. Containers that do not have drainage holes should be avoided.
Select a well-drained potting soil that is also free from pests and disease. Purchase a high quality potting mix at your local garden center or greenhouse. You also can mix your own potting soil by mixing equal parts of peat, perlite and pasteurized garden soil. Some bulbs will force well without soil. Hyacinths are often forced in a bulb glass.
Fill the container halfway or more with soil then place the bulbs pointed side up in the pot. Be careful not to injure the bulbs in the process. To assure a great floral display, plant the bulbs closely together. Five or six tulip or daffodil bulbs can be planted in a 6-inch container. After planting, the top of the bulb should show above the soil surface. Generally, a single type of bulb is planted in each container, but feel free to pot up a mixed bulb container for a rainbow of flower colors. When mixing different bulbs, be sure to plant the smaller bulbs along the edges of the container to ensure they will be visible. When planting is completed, water the bulbs thoroughly.
Spring flowering bulbs like tulips, daffodils, hyacinths, crocus and grape hyacinths require a cold period or simulated winter before flowering. Cold temperatures are essential for forcing spring-flowering bulbs as flower initiation and root growth occur during this period. A temperature of 40 - 45 degrees F for 12 - 16 weeks in complete darkness is required for cold storage. Some of the best places for cold storage include a refrigerator, a cool cellar or an unheated garage. The bulbs should not be allowed to freeze during this period. Continue to water the bulbs when needed during cold storage as well.
After 12 - 16 weeks of cold storage, begin to remove some of the containers. Place the bulbs in a cool (60 degrees F) dark room for a couple of days to allow them to gradually adjust to warmer temperatures. Transfer them to a well-lit window at room temperature (65-70 degrees F). Protect the bulbs from hot or cold drafts as these conditions may damage the newly emerging foliage and flowers. Rotate the container regularly to prevent the plants from bending. Flowering can be expected in three to five weeks after transfer to a warm well-lit location. Once flowering begins the bulbs can be moved to a more visible location. They make great centerpieces for the table in late winter and early spring. For a succession of blooms, remove pots from storage at two-week intervals.
Some of the spring-flowering bulbs like daffodils, crocus and grape hyacinths can eventually be planted outside after forcing. Since forcing tends to exhaust the bulb's food reserves, these bulbs may not bloom the first spring. However, many do eventually bloom well in the garden. Tulips and hyacinths generally do not return well after forcing. Therefore, new bulbs should be purchased every year for forcing.
Amaryllis and Paperwhites
Amaryllis and paperwhites are forced differently than spring-flowering bulbs. Amaryllis and paperwhites do not require cold treatment. Therefore, they will initiate growth shortly after potting. With amaryllis bulbs, the top third to half of the bulb should be above the soil surface. Paperwhites can be forced successfully while potted in pebbles instead of soil. After potting amaryllis and paperwhites, transfer them directly to a well-lit warm location. Do not mix amaryllis and paperwhite bulbs in the same container with spring-flowering bulbs since the spring flowering bulbs will require a cold treatment.
Amaryllis bulbs should be left in their containers and allowed to maintain active growth throughout the summer. Amaryllis bulbs can be easily saved and forced for many years. Paperwhites should be discarded after flowering since they are not hardy outdoors and can not be forced again.
Plan now for brightening the indoor landscape this winter with bulbs.
ml: isugarden
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