Winter will soon be here and with any luck our gardens will be covered with a blanket of snow. While many gardeners are happy to have a break from the garden during the fall months, winter brings longing to see new growth and color in anticipation of spring. Forcing bulbs for indoor blooms can help tide one over during the dark days of winter. Additionally, they can add an element of festivity for special occasions.

Fall is the best time to plant bulbs for spring color in the garden and also begin the process of forcing bulbs for winter blooms indoors. Forcing refers to the process of artificially cooling bulbs for a period of time and then gradually exposing them to a warm and moist environment; in essence, mimicking winter and the transition to spring. The required cooling period varies from none, like paperwhites (Narcissus) and amaryllis, to 14-16 weeks for certain tulips. Most bulbs suitable for forcing (e.g., Crocus, Hyacinths, Grape Hyacinths, Dutch Iris) require a cooling period of approximately 3 months at an environmental temperature of approximately 40 degrees F. Hence, it is advisable to plan ahead.

When purchasing bulbs, select varieties that state they are good for forcing or those that bloom early. Store bulbs in a cool, dark well ventilated area (e.g., garage or basement) until you are ready to plant them. When planting, select a container that is about twice the depth of the bulb. After ensuring that the container has good drainage, plant the bulbs in soil with their tips just barely visible at the top (except for amaryllis where up to one half of the bulb may be exposed). Water the pot thoroughly and begin the cooling period, periodically checking the soil to make sure it has not completely dried out. Keep the bulbs at a constant temperature of 40-48 degrees F. The bulbs show no outward growth during this period, but should be developing a root system that will support blooms once exposed to a warm environment and watered regularly.

Those who prefer a more immediate reward can find pre-potted bulbs (commonly amaryllis or paperwhites) that you can simply place in a sunny location, water and watch grow. Previously forced bulbs (e.g., hyacinths) are also available and lend themselves to decorative plantings in glass containers, on glass beads or pebbles. Water these and watch them grow and provide support to the blooms if needed.

Once the blooms are finished, wait for foliage to yellow so that energy is returned to the bulb. When the ground is workable, winter hardy bulbs may be planted in the garden. While not all will bloom again, many will. Non-hardy bulbs such as paperwhites are typically a single season plant. Amaryllis, not hardy in Colorado, may be planted outside in a warm sunny location during the summer. After, place in a dark, cool environment for eight to 12 weeks. The plant will go dormant, replenish itself and be ready to bloom again the following winter.

For more information on forcing bulbs indoors, visit planttalk.org and read topic #1319, “How to Force Bulbs Indoors.”

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

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This page updated: October 10 , 2007