Clematis flowers are famous for their beauty and decorative value. Clematis plants (Clematis spp.) Are fast, woody vines that grow as herbaceous perennials in U.S. Department of Agriculture plant hardiness zones 5 or 4 through 8 or 9, depending on the particular variety. Over 200 wild clematis species and 400 named cultivars exist. Their heights vary substantially, with some only two or three feet tall while others can achieve a height of 20 or 30 feet.
Tall Clematis Varieties
One group of clematis hybrids (C. x jackmanii), generally referred to as the Jackman hybrids, are especially vigorous growers that can grow up to 10 feet tall in a single season and also reach a mature height of 20 feet. They have a tendency to bloom in late spring or early summer, creating flower buds on the previous season’s increase that open to 5- to 7-inch-wide, violet-purple flowers. Another plant called anemone or grandiflora clematis (C. montana f. grandiflora) is an extremely tall variety, reaching a height of 24 to 40 feet when specified support or allowed to climb to a massive tree. Its flowers are pure white, fragrant and about three or four inches in diameter. Finally, sweet autumn clematis (C. terniflora) can reach 30 feet in height and has masses of fragrant, 1-inch-wide white blooms in early fall.
Several clematis varieties grow to a medium height of 6 to 12 feet at maturity, which makes them useful for trellises or fences, or as a decorative plant by a mailbox or porch pole. The cultivar “Edouard Desfosse” (C. “Edouard Desfosse”) is also a good example of the type, reaching a height of between 6 and 8 feet. It has big, deep purple flowers and is unusual in its ability to blossom on both old and new wood. The blue jasmine clematis (Clematis crispa) is just another medium-height clematis, growing between 6 and 10 feet tall. Though it generally grows in USDA zones 6 through 9, this variety reacts to the ground over winter and also reappears in spring. Its fragrant flowers are bell-shaped and pale blue or violet, with white petal undersides.
Short Clematis Varieties
A couple of kinds of clematis have a tendency to be short, ranging from 2 to 6 or 5 feet in height. The hybrid cultivar “Betty Corning” (C. crispa x C. viticella) is about 5 feet high and has pale lilac flowers which are single, bell-shaped and nodding, with petals whose hints recurve. “Bourbon” clematis (C. “Evipoo18” Bourbon) is 4 to 6 feet tall, a good selection for patio containers and has showy, big red-purple flowers. Eventually, Fremont’s leather flower (C. fremontii) is an unusual clematis that’s only 12 to 18 inches tall and doesn’t climb. Its flowers are white or purple and bell-shaped, typically appear separately and are followed by attractive seed heads.
Clematis plants generally flower best when grown in full sunlight, but they can withstand partial shade to get a portion of the day. They also prefer shade above their roots and should be sited in the shade of a stone or with other short, leafy crops to shade their origin zone. They require abundant moisture when growing and do best in light, well-drained dirt. Adding a two- to 3-inch layer of organic mulch annually can help keep roots nourished while retaining soil moisture. While normally problem-free, clematis plants are susceptible to a fungal disease called clematis wilt that triggers stems and leaves to turn black and die. It’s best controlled by pruning away stems as soon as they show signs of infection.