How to Force Bulbs

Elaine Feinberg
Frederick County Master Gardener Program

Many bulbs can be forced to bloom indoors. It is fun to do and very rewarding. Most hardy bulbs take anywhere from 8 to 16 weeks of cooling (with the majority at about 10-12 weeks) before they can be forced to bloom. The ideal cooling temperature is 33-45 degrees. If you order early, some catalogs will identify which bulbs do well forced. Here are some: several trumpet daffodils, such as Dutch Master(yellow) and Mt. Hood(white) and Salome(white with soft pink trumpet). Among the tulips the Early Singles, Triumphs and some Darwin Hybrids and Parrots are easiest to force. Many crocuses are easy including C.chrysanthus Blue Pearl and C. vernus varieties such as Remembrance and Pickwick.

The container you choose can be clay or plastic with good drainage. It is best to plant one type of bulb per pot using potting soil. After planting the bulb in the pot, moisten the soil and start the cooling procedure. You can place the pot, covered with plastic, in the refrigerator or in a root cellar or garage. It should be checked every few weeks for moisture. After about 8 weeks for the smaller bulbs and 12 to 14 weeks for the larger ones, check for the beginnings of top shoots. When they reach about one inch, take the plant out of the cold but let it adjust to the warmer and brighter room gradually. Fertilize each time you water. It should take about another month to bloom.

Some gardeners cool the bulbs outside, either by burying the pot about one foot into the soil (covered with dry leaves and plastic) or, in our zone, keeping the pot above the ground but covering with about a foot of dry leaves and a tarp. Proceed as above when the bulbs begin to shoot up.

There are several bulbs which do not require cooling. The two that will be described are Hyacinths and Paper-Whites.


You must buy bulbs which have been prepared for forcing into early blooming. They have received special treatment prior to selling to promote premature bud formation. During the dormant period they were lifted and subjected to a higher temperature than they would normally experience. You can force them quickly and easily by growing them in water. You should use an hourglass-shaped container. The glass should be filled up to its narrow waist with water with a small piece of horticultural charcoal added to fight off fungal problems.

The bulb is placed in the upper section of the vase so that the water is just touching its base. Put the glass in a dark corner to promote strong root growth. In about 3 weeks the Hyacinth should be ready to bloom. Place the glass in a bright sunny location - about 60-70 degrees. Rotate the glass often and maintain the water level. Discard the bulb after blooming. Bulbs grown in this way will not rebloom.

Paper-Whites (Narcissus taxetta)

Again, they are grown in water, best in a wide shallow container. Glass is preferred. Put in 2 inches of pebbles and sprinkle on horticultural charcoal. Place the bulbs on the pebbles, growing tips up. They should not be closer than 1/2 inches apart. Keep adding pebbles until the bulbs are firmly positioned. Add enough water to reach the bottom of the bulbs. Then place in a cool, dark spot. When sprouts appear (in about 2 weeks), move to a cool bright spot. Flowers should appear in 4 weeks. Keep water level constant and rotate the pot daily.

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