Gerald L. Klingaman
Plant Common Name
Clematis is a genus of about 300 species grown for their eye-catching flowers. Most are twining vines but some are herbaceous perennials and a few are shrubby. They can be evergreen or deciduous and exist in temperate regions worldwide. There are thousands of hybrid cultivars bred exclusively for their beautiful, showy flowers.
Species in this large genus come in many diverse forms. The leaves are usually opposite on the stem and may be rounded, elliptical, heart or lance shaped and simple, divided or lobed. The leaf edges may be smooth or toothed and the surface fuzzy or smooth.
The flowers are as variable as the leaves. They may be large or small and saucer, cup or bell-shaped. All have tepals (petal-like structures around a flower) that come in a wide range of colors. The blooms often have a flourish of filamentous or feathery reproductive structures in the middle of the flower. The flowers can be borne singly or in clusters. The fruits consist of dense spidery clusters of silvery filamentous seeds.
Culture and hardiness is species and cultivar dependent, however most hybrid Clematis have been divided into three groups based on bloom-time and pruning requirements:
Group 1: Early blooming Clematis that have flowers are borne on the previous year’s growth. Typically, the flowers are single and bell-shaped. The vines are often evergreen, though a few are deciduous. Prune Group 1 plants immediately after flowering.
Group 2: Late spring to summer blooming Clematis that flower on the previous year’s wood, later in the season they may bloom again on the current year’s wood. The flowers are often large, saucer-shaped and the vines deciduous. Prune Group 2 plants immediately after flowering.
Group 3: Late-blooming Clematis that flower on the current year’s growth. Typically, the flowers are large and saucer-shaped. They have various forms including doubles. The plants are often deciduous. Prune Group 3 vines hard just before growth starts in the spring.
Generally, Clematis grow best in sites with full sun and fertile, well-drained soil. Most prefer neutral to alkaline conditions, more acid soils induce nutrient deficiencies. They grow and flowers best if their roots remain cool under a vegetative layer or thick mulch. Many cultivars require some cold weather for best growth and flowering. Most Clematis add a vertical element to the garden and look best when trained on a fence, trellis or pergola.