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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Forcing and Planting Spring-Flowering Bulbs

This article was published originally on 8/27/2004

Tulips, daffodils, crocuses, and other spring-flowering bulbs are a welcome sight in spring. Gardeners can also enjoy spring-flowering bulbs during the winter months by forcing them indoors.

For best selection of bulbs, visit local garden centers in September as soon as the bulbs arrive. Select large, firm bulbs. Avoid small, soft, or blemished bulbs. When purchasing bulbs from mail-order companies, immediately check the bulbs upon receipt. If they are soft or moldy, send them back. Store purchased bulbs in a cool, dry, well-ventilated location, such as the garage, until they are planted.

Forcing Spring-Flowering Bulbs Indoors

Spring-flowering bulbs that can be forced indoors include tulips, daffodils, hyacinths, and crocuses. While many bulb varieties can be forced, best results are obtained by selecting varieties recommended for forcing. To enjoy spring-flowering bulbs in winter, gardeners must begin the forcing process in late summer or early fall. Gardeners need good quality bulbs, a well-drained potting mix, and containers with drainage holes in the bottom.

Begin by partially filling the container with potting soil. Then place the bulbs on the soil surface. Adjust the soil level until the tops of the bulbs are even with or slightly below the rim of the container. Place additional potting soil around the bulbs. However, don't cover the bulbs completely. Allow the tops (noses of the bulbs) to stick above the potting soil. After potting, water each container thoroughly.

In order to bloom, spring-flowering bulbs must be exposed to temperatures of 40 to 45 F for 12 to 16 weeks. Possible storage sites include the refrigerator, root cellar, or an outdoor trench. During cold storage, water the bulbs regularly and keep them in complete darkness.

Once the cold requirement has been met, begin to remove the potted bulbs from cold storage. For a succession of bloom, remove pots from storage at 10 to 14 day intervals. Place the bulbs in a cool (50 to 60 F) location that receives low to medium light. When the bulbs begin to grow, move the plants to a slightly warmer area that receives bright light. Keep the potting soil evenly moist during the forcing period. Flowering should occur in 3 to 4 weeks.

Tulips and most other spring-flowering bulbs are normally discarded after forcing. Attempts to save forced bulbs are usually unsuccessful, as many don't bloom again when planted outdoors. Forced daffodils, however, can often be successfully planted outdoors.

Planting Spring-Flowering Bulbs Outdoors

October is the ideal time to plant spring-flowering bulbs in Iowa. When planted in October, spring-flowering bulbs have sufficient time to develop a good root system before the ground freezes in winter. If weather permits, bulbs can be planted as late as mid- to late- November. However, late-planted bulbs will emerge and bloom later than normal the following spring.

Most bulbs perform best in partial to full sun. Bulbs also need a well-drained, fertile soil. Poorly-drained soils can often be improved by incorporating organic matter, such as compost or peat.

Plant spring-flowering bulbs in clusters or groups to achieve the greatest visual impact in the garden. When planting daffodils or tulips, plant 10 or more bulbs of the same variety in an area. Smaller growing plants, such as grape hyacinths and crocuses, should be planted in clusters of 50 or more bulbs. Plant bulbs at a depth equal to 3 to 4 times their maximum bulb diameter. Accordingly, tulips and daffodils should be planted 6 to 8 inches deep, crocuses and grape hyacinths only 3 to 4 inches deep. Large bulbs, such as tulips and daffodils, should be spaced 4 to 6 inches apart. A three-inch-spacing is adequate for crocuses, grape hyacinths, and other small bulbs.

After planting, water the bulbs periodically (if fall weather is dry) to promote good root development.



This article originally appeared in the 8/27/2004 issue.

Year of Publication: 
2004
Issue: 
IC-491(21) -- August 27, 2004