Clematis vines are woody members of the buttercup family Ranunculaceae. The colorful portion of the flowers is made up of sepals instead of petals. Petals are absent. Flowers may be single, double, or even triple. All colors are available. The one drawback of the Queen of Vines is their lack of fragrance in the large flowered varieties. Small-flowered species offer a range of fragrances from almond to hot cocoa. Besides having attractive flowers, clematis seedheads are attractive as well. Foliage ranges from a medium to dark-green. Many have entire leaves; however, some species may have serrated or lobed foliage. Clematis climb by twisting their petioles around a support. They do not twine or root as do other climbers. Over 250 species and at least 5000 varieties are available which bloom from May until frost.
Clematis are divided into three main groups based on season of bloom. Group one produces its flowers on short flower stalks emerging directly from the leaf axil bud, usually on previous season's stems. These species bloom in early spring. They should be pruned immediately after flowering if they need shaping or trimming. The second group of clematis flowers on shoots that have grown during the current year. These should be cut back to two feet in early spring if they did not dieback to the ground during winter. Most of these varieties bloom in midsummer. Group three flowers in late summer and fall. If left unpruned they begin growth from where they flowered the previous season and become bare at the base with flowers only at the top. These varieties should be pruned in early spring above the lowest pair of strong buds on each stem.
The best time to plant clematis is early spring. However, containerized plants can be planted throughout the growing season. They should be planted where they will receive at least six hours of sunlight a day, east and south exposures are ideal. The crown should be planted an inch below the soil surface to encourage multiple shoots and provide winter protection. If roots are crowded, straighten them out before planting. The planting site should be well drained yet have good water holding capacity. Amend the area with compost or peat moss to improve drainage and water retention. Do not add lime. Clematis prefer neutral to slightly acidic soils. Topdress with a 1-2-1 fertilizer in spring and fall to encourage vigorous growth. Avoid fertilizers high in urea and ammonia. If flowers fail to appear, fertilization and proper pruning should get the plant back on track. Clematis require at least an inch of water per week and like their root systems kept cool. Mulching is extremely important. Provide a support structure and secure the vine to it while small. This will encourage it to begin climbing. Propagation is best done by layering or growing from seed. Large plants can be divided; however, it isn't an easy task.
Avoid buying plants in flower. After planting the flowers will drop and the plant will remain somewhat stunted for the rest of the season. Clematis are relatively pest free. The one problem they experience is clematis wilt caused by Asochyta clematidina. Entire stems may suddenly collapse. Remove the affected stems at ground level and water thoroughly. This problem only occurs on large-flower varieties and usually appears just as the flower buds begin to swell.
Clematis are useful, beautiful, and tough climbing plants for many landscape situations. It has rightly earned the title, Queen of Vines.
This article originally appeared in the May 12, 1993 issue, pp. 1993 issue, pp. 67-68.