Do Tulip Bulbs Need Cold Moist Stratification?

Garden Plants

• Tulips grown in a garden bed naturally receive cold treatment during the winter months, as long as soil temperatures drop below 45 degrees Fahrenheit for at least eight weeks. In warmer climates, the bulbs require indoor stratification and late winter planting. Planting new bulbs in the garden in fall gives them time to experience the cold temperatures necessary for breaking dormancy and putting on growth in spring. Plant tulips bulbs in the garden in midfall, setting the bulbs so that the pointed tip is about 3 inches beneath the soil surface.

  Water the soil until it feels moist after planting, and cover the bulbs with 2 inches of mulch. The bulbs usually don't require any additional watering until they begin growing in late winter.

Outdoor Pots

• Pot-grown tulips for indoor forcing also require a cold treatment. You can provide this treatment outdoors if temperatures remain below 45 F for at least two months. Tulips can tolerate close spacing in pots, so plant the bulbs with the tips just beneath the soil surface and spaced only 1 or 2 inches apart.

  The soil requires thorough watering so that it's moist throughout. Placing the pots in a loosely closed plastic bag helps retain moisture during cold treatment so that you only have to water the soil infrequently if it begins to dry. You can also place the pots outdoors uncovered in a shaded area where winter rain keeps the soil moist without flooding the pots.

Indoor Stratification

• Indoor cold treatment allows you to force dormancy in warmer climates, either for late winter garden planting or forcing potted blooms indoors. For garden planting, store the bulbs in a sealed plastic bag filled with damp peat moss. Refrigerate the bulbs for eight to 10 weeks, and then plant them normally in the garden in late winter.

  You can also pot up the bulbs for indoor forcing and seal the pot in a plastic bag. Keep the bagged pot in the refrigerator for eight to 10 weeks before uncovering it and moving it to a warm room where it receives bright, indirect light.

Basic Care

• Tulip plants require only basic care when they begin growing after cold stratification. Outdoor bedding plants require about 1 inch of water weekly, or enough to moisten the top 6 inches of soil. Indoor plants need to be watered when the top 1 inch of soil feels dry.

  Forced tulip bulbs usually deplete all their energy and are only good for flowering for one year. Bedding plants may return for several years if the bulbs receive sufficient cold treatment each winter in the bed. Cut back the flowers of outdoor tulip plants after bloom, but leave the foliage in place until it dies back naturally.