Brightly colored tulips are a sure sign that spring has arrived in the Midwest. However, it's not necessary to wait until April or May to enjoy these spring-blooming favorites. Tulip bulbs can be forced indoors to brighten the cold, gray days of winter. If properly planned, tulips can be enjoyed indoors from January through March.
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. Tulip bulbs can also be purchased from mail-order companies. The best types of tulips for forcing include the Triumph, Single Early, Double Early, and Darwin Hybrids.
In addition to high quality bulbs, a well-drained commercial potting mix and suitable containers are necessary to successfully force tulips indoors. Containers for forcing can be plastic, clay, ceramic, or metal. Almost any container can be used as long as it has drainage holes in the bottom.
Begin by partially filling the container with potting soil. Then place the tulip bulbs on the soil surface. Adjust the soil level until the tops of the bulbs are even or slightly below the rim of the container. The number of bulbs to plant per pot depends on the size of the container. Generally, 4 to 5 bulbs are placed in a 5-inch-diameter pot, 6 to 7 in a 6-inch-diameter pot. When placing tulip bulbs in the container, position the bulb so the flat side of the bulb faces the wall of the pot. When positioned in this way, the large lower leaf of each bulb will grow outward over the edge of the container forming an attractive border around the edge of the pot. Once properly positioned, place additional potting soil around the bulbs. However, do not completely cover the bulbs. Allow the bulb tops (noses) to stick above the potting soil. For ease of watering, the level of the soil mix should be1/2 to 1 inch below the rim of the container. Label each container as it is planted. Include the name of the variety and the planting date. After potting, water each container thoroughly.
In order to bloom, tulips and other spring-flowering bulbs must be exposed to temperatures of 40 to 45ºF 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.
Begin to remove the potted tulip bulbs from cold storage once the cold requirement has been met. At this time, yellow shoots should have begun to emerge from the bulbs. Place the tulips in a cool (50 to 60ºF) location that receives low to medium light. Leave them in this area until the shoots turn green, usually 4 or 5 days. Then move them to a brightly lighted, 60 to 70ºF location. Keep the plants well watered. Turn the containers regularly to promote straight, upright growth. On average, flowering should occur 3 to 4 weeks after the bulbs have been removed from cold storage. For a succession of bloom indoors, remove pots from cold storage every 2 weeks.