Gardeners in temperate climates utilize tulips (Tulipa spp.) as reliable spring-flowering plants to announce the end of winter. With origins in the highlands of central western Asia, tulip bulbs were traded to Europeans, who grew them for their colorful blooms. The Dutch became known as the world’s keeper and breeder of tulip bulbs, producing hundreds of hybrid varieties, many for use only as cut flowers. Each bulb produces a flower once per year.
Gardeners plant tulip bulbs in fall when the bulbs are dormant. Exposure to cool, moist soil over the winter months causes initial roots to grow. Cold temperatures lead to formation of the flower bud inside the bulb, which emerges in late winter or early spring once temperatures warm sufficiently. After flowering, the tulip foliage remains for several weeks to photosynthesize light. The carbohydrates made in the leaves re-energize the new young underground bulblets developing from the mother bulb. The foliage withers away naturally by early summer and the bulb again rests dormant.
Because of decades of complex breeding of tulips by horticulturists in many countries such as The Netherlands, a wide array of tulips exist today. Various flower colors, shapes and petal-forms exist, all blooming at times generally called early, mid- or late season. Early-season tulip varieties bloom in March in the southern U.S. but in mid to late April farther north. Midseason and late season tulips bloom in sequence after early tulips, with all tulips finishing blooming by mid-April in the South but by late May closest to the Canadian border.
Wild species tulips tend to return year after year, being reliable perennial flowers. Extensive breeding of tulips for generations led to genes that horticulturists preferred for flower color or form, not for ability to remain perennial. Therefore, many modern tulip varieties’ bulbs do not persist well and do not consistently return with a flower the second year. Cool, moist soil promotes perennial return of tulips. Often, gardeners discard tulip bulbs after they bloom and plant plump, fresh bulbs each fall that were raised in ideal conditions in The Netherlands.
Florists force tulips into bloom at other times of year to sell as potted gift plants. It involves chilling bulbs for 10 to 12 weeks and then exposing them to cool, springlike temperatures in greenhouses. To keep potted tulips in flower for the longest display, temperatures in the 50 to 60 degrees Fahrenheit range keep petals looking nice the longest. Heat causes tulip flowers to mature more quickly, opening and shedding petals faster than if in cooler conditions.