Cool-season bulb plants, tulips (Tulipa spp.) were first discovered in eastern Turkey. Although tulips grow in U.S. Department of Agriculture plant hardiness zones 3 through 8, they don't bloom reliably in mild-winter climates unless you dig them up and refrigerate them. In regions where temperatures rarely drop below 25 degrees Fahrenheit, you'll need to chill the bulbs if you want to see flowers each year.
Prepare Bulbs for Digging
Tulips spend their energy while they're flowering, and they need to replenish this energy after their spring show. If you plan to dig, store and replant your tulip bulbs, leave them in the ground until the leaves yellow and wither. As long as the leaves are green, they're photosynthesizing -- building energy stores for the next season's flowers. Clip the spent flower off the stalk to prevent seed formation. Setting seed takes energy and weakens the bulb.
Dig and Store Tulip Bulbs
If you live in USDA zone 8 or cooler and your bulbs are planted in an area of your yard that remains relatively dry, you can leave the bulbs in the ground until June or July. If you live in a warmer climate or your soil will stay moist, dig the bulbs as soon as the leaves wither. Use a garden fork to dig under the bulbs and lift them from the ground. Separate the bulbs. Remove roots and loose soil from the bulbs and store them in a dry place with good air circulation in mesh bags or shallow wooden crates, with bulbs no more than 5 inches deep in the container. Avoid storing bulbs where temperatures exceed 90 degrees Fahrenheit.
Allow Tulips to Chill
If you live in USDA zones 8 through 10, plant tulips between early November and early January. In colder climates, plant tulips in early fall.
Count back 16 to 18 weeks before planting time for your area, and place the bulbs in ventilated bags or dry peat moss and put them in your refrigerator, an unheated building or other spot where temperatures remain between 35 and 45 F. Keep the bulbs chilled until it's time to plant.
Prepare the Bed
Fertilize the tulip bed at planting time by digging in a 2-inch layer of compost or well-rotted cow manure, or use a 10-10-10 or 10-15-10 commercial fertilizer after planting. Apply commercial fertilizer at the rate of 2 pounds per 100 square feet, or follow label instructions. Spread the fertilizer on top of the bed after planting, then water the area.
Set bulbs 6 to 8 inches deep, with the pointed end facing up. If you plan to mulch, add the mulch depth to your calculation. For example, if you plan to add 2 inches of mulch, plant the bulbs 4 to 6 inches deep. After green shoots emerge, apply a balanced, slow-release fertilizer such as 10-10-10 or 10-15-10 at the same rate you used at planting time.