Force Bulbs for Indoor Color - Indiana Yard and Garden - Purdue Consumer Horticulture

Force Bulbs for Indoor Color

Now’s the time to stock up on the spring-flowering bulbs that will provide a burst of color just when we need a lift from the winter doldrums. But you don’t have to wait until spring to enjoy these blooms if you prepare a few for forcing indoors. In fact, you can have a bouquet in time to decorate for the holidays.

Hardy bulbs such as tulips, daffodils, hyacinths and crocus require a cold period of 10 to 13 weeks to cause the bulbs to initiate flowers and establish roots. Pot the bulbs in a container that has drainage holes at the bottom. You can place that pot inside a more decorative pot at forcing time if desired, but it is critical that excess water have a way to drain. Specific planting directions vary with the type of bulb, as follows:

Tulips: Place three bulbs in a 5-inch pot, with the flattened side of the bulb toward the wall of the pot (so the large, floppy leaf will grow towards the outside of the plant). Allow the tips of the bulbs to show above the soil.

Hyacinths: Place three to four bulbs in a 7-inch pot or one bulb in a 4-inch pot. Allow the bulb tips to show above the soil.

Daffodils: Place three or four bulbs in a 7-inch pot, allowing half of the bulb to show above the soil.

Crocus, Snowdrops and Grape Hyacinth: Place five to seven bulbs in a 7-inch pot, 1 inch below the soil surface.

Moisten the soil and place the potted bulbs in cold storage (40-50 degrees Fahrenheit) for 10 to 13 weeks (The length of chilling depends on the type of bulb. Thirteen weeks is adequate for just about all types.) If you don’t have enough space in the refrigerator to accommodate your bulbs, you could chill them in an outdoor trench. Dig a pit about 15 inches deep and line the bottom and sides with chopped leaves, straw or other loose mulching material to allow for easier digging when the soil is frozen. Place the pots in the trench and then cover with additional mulch. Keep in mind that outdoor temperatures may not yet be cool enough to get them ready in time for the holidays. If timing is critical, check your garden center or mail-order supplier for pre-cooled bulbs.

After the chilling period, bring the pots indoors, moisten if needed and place at room temperature in a bright location. The bulbs will likely have produced yellowish sprouts, which will turn green upon exposure to light. Blooms should appear within two to three weeks. Keep the plants in a cool location, away from heat vents and direct sunshine, to prolong their beauty.

It’s usually best to discard hardy bulbs after forcing since their food reserves are used up. But, if you just can’t make yourself throw them away, plant them outdoors after the blooms fade. Remove the pots, and plant where the foliage will receive maximum sunshine to help rebuild the bulb’s food reserves. It may take a couple of years or more for the bulbs to rebuild enough energy to put on a good show.

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