Color the landscape with clematis

Clematis are easy to grow. Plant them in soil that has been amended with organic matter in an area with their preferred light conditions, and clematis will show off their beautiful blooms in the landscape year after year.

Clematis favor a spot where their roots reach into cool, evenly moist soil, but their flowers prefer to bathe in bright, warm sunlight. Create these conditions by planting clematis in full sun and then applying a 2- to 3-inch layer of mulch over their roots - or by planting other perennials around them to shade their roots.

Prepare the soil before planting by digging a hole 18 to 24 inches wide and deep. Mix plenty of organic matter with the excavated soil. Position the vine a couple of inches deeper than it was in its pot and use the amended soil to fill the hole. Water thoroughly. If the clematis is already growing on a small trellis in its pots, leave it in place when planting. Set the stake at an angle to direct the vine to its permanent structure.

Clematis vines must be supported in some fashion. The type of structure depends on the variety of clematis chosen. Smaller cultivars grow on simple poles or small obelisks; larger types require trellises, fences or arbors; the most vigorous varieties need pergolas or large, strong trellises.

The twisting stems of clematis vines wind their way up their supports. Structures should include bars no thicker than the diameter of a pencil, small enough to be encircled by clematis petioles. If a structure is of bolder construction, attach chicken wire to give clematis something to wind itself around.

Pruning clematis strikes fear in the hearts of many gardeners. Clematis are divided into pruning groups which dictate the method and timing of pruning. Many gardeners can't remember the name of their particular clematis let alone its pruning group. Instead use these easy-to-remember guidelines.

Early-blooming varieties begin flowering in May and pruning is not required but should be pruned, if desired, as soon as they are done flowering. They set buds for the following year on previous season's growth.

Some clematis have two distinct periods of bloom because they bloom on both old and new growth. These only require pruning to maintain their form.

Late-flowering clematis begin to flower the end of June or early July and may continue to bloom until frost. These bloom on new growth and should be pruned in late winter or early spring to encourage the growth of many flowering stems. Begin at the ground, follow stems upward to the first strong pair of buds and prune just above those buds - usually 2 to 3 feet above the ground.

Grown on trellises, clematis are an ideal solution for narrow spaces where screening is desired. An unsightly fence becomes a landscape feature with clematis. Small types are suitable for growing in containers. Larger cultivars grow through shrubs. Plant a clematis on a large obelisk as a focal point in a perennial border or let it sprawl across the floor of the border. A clematis-covered arbor is a dramatic and welcoming entry to the backyard.

Choose from cultivars sporting petite, 1-inch blossoms to massive, near salad-plate size; flowers in soft pastel to boldly bright blooms; and vertically challenged varieties struggling to reach 3 feet to the ambitious sweet autumn clematis stretching 30 feet long or more.

• Diana Stoll is a horticulturist, garden writer and speaker. She blogs at gardenwithdiana.com.