Tulips are spring-blooming perennials that grow from bulbs. Depending on the species, tulip plants can grow as short as 4 inches (10 cm) or as high as 28 inches (71 cm). The tulip’s large flowers usually bloom on scapes or subscapose stems that lack bracts. Most tulips produce only one flower per stem, but a few species bear multiple flowers on their scapes (e.g. Tulipa turkestanica). The showy, generally cup- or star-shaped tulip flower has three petals and three sepals, which are often termed tepals because they are nearly identical. These six tepals are often marked near the bases with darker colorings. Tulip flowers come in a wide variety of colors, except pure blue (several tulips with “blue” in the name have a faint violet hue).
The flowers have six distinct, basifixed stamens with filaments shorter than the tepals. Each stigma of the flower has three distinct lobes, and the ovaries are superior, with three chambers.The tulip’s fruit is a capsule with a leathery covering and an ellipsoid to subglobose shape.Each capsule contains numerous flat, disc-shaped seeds in two rows per chamber.These light to dark brown seeds have very thin seed coats and endosperm that does not normally fill the entire seed.
Tulip stems have few leaves, with larger species tending to have multiple leaves. Plants typically have 2 to 6 leaves, with some species having up to 12. The tulip’s leaf is strap-shaped, with a waxy coating, and leaves are alternately arranged on the stem. These fleshy blades are often bluish green in color.
Tulips are indigenous to mountainous areas with temperate climates and need a period of cool dormancy, known as vernalization. They thrive in climates with long, cool springs and dry summers. Although perennials, tulip bulbs are often imported to warm-winter areas of the world from cold-winter areas, and are planted in the fall to be treated as annuals.
Tulip bulbs are typically planted around late summer and fall, in well-drained soils, normally from 4 inches (10 cm) to 8 inches (20 cm) deep, depending on the type planted. In parts of the world that do not have long cool springs and dry summers, the bulbs are often planted up to 12 inches (30 cm) deep. This provides some insulation from the heat of summer, and tends to encourage the plants to regenerate one large, floriferous bulb each year, instead of many smaller, non-blooming ones. This can extend the life of a tulip plant in warmer-winter areas by a few years, but it does not stave off degradation in bulb size and the eventual death of the plant due to the lack of vernalization.