Tulips (Tulipa species) are one of the first signs of spring and are the world's most financially important ornamental flower crop, according to Floridata. These colorful bulb flowers are a favorite with home gardeners not only for their beauty, but for the fact that they are easy to plant and grow. Tulips comprise more than 2,000 species and cultivars, which have been divided into 15 classifications. The flowers are classified in part by their appearances.
Tulip bulbs in general are shaped like teardrops, with a pointed tip on one end and a much wider, rounded edge on the opposite end. Depending on the variety, the point at the tip may be very apparent, or one end might be a little less rounded than the other. The bulbs are covered with thin layers of papery skin that flakes off easily. They should be planted with the pointed side facing upward, at least 6 inches below the surface of the soil.
In general, the larger the bulb, the bigger the tulip will be, and this is especially true when it comes to bloom sizes. Tulips also range widely in height, from the small, 4-inch tall Kaufmanniana tulip to several varieties, including the popular Darwin hybrids, that can reach up to 30 inches in height.
Tulip leaves are green, but the color can vary from a deep, dark green to a bright or light shade. The leaves can be as long as the stems or quite a bit shorter, depending on the variety, and range in width from less than an inch to 2 or 3 inches. They can also appear with straight edges or wavy edges, again depending on the type of tulip.
All varieties of tulips, save the one, have just one flower that sits atop a sturdy stem. The appropriately named multiflowering tulips have branching stems that produce three or four flowers on each plant. The shape of the tulip flower can appear much like a lily, a cup, or an inverted, ruffled skirt. While most tulips have a single layer of smooth-edged, ovate petals, there are some exceptions. The Parrot tulip has petals that have long fringes (also called "feathers") on the edges, or petals that are twisted or curled. Double-late tulips have so many layers of petals that they look more like peonies, according to Iowa State University. The stamens on tulips are quite obvious, although the flowers themselves have no nectar.
Tulips come in almost any shade imaginable, save blue, according to the University of Illinois. Many are variegated, such as Greigii tulips, which can be striped or appear to have blotches of contrasting color. Some varieties of Parrot tulips have green spots at the bottom of each individual petal. Home gardeners tend to choose tulips as a group by the hue rather than the color. Many prefer pastel colors only, while others choose only varieties that are bright and bold.