Hardy clematis eager climber, active bloomer

Soon, when the snow recedes and the ground begins to slowly warm, tiny green buds of the hardy clematis will poke through the soil or swell on the vine. The plant’s slender vines will weave in and out of a trellis, around the posts of a porch or up the side of an arbor. They wind their way down the fence, over the rock wall or, if no support is given, along the ground. Showy blooms in blue, pink, white, burgundy or a combination of bicolor shades will last throughout summer.

Clematis has somewhat of a reputation for being a difficult plant to grow, but I think this label is an unfortunate injustice. I’ve seen healthy plants growing beside the porch of an old farmhouse untouched by the gardener for years. I’ve seen them ramble over arbors and creep along stonewalls without so much as a dose of fertilizer or a nip from the pruning shears. Keep the lawnmower a goodly distance away from them, I say, and let them scramble over walls, through lesser shrubs, over mailboxes and into infinity. Let this ornamental vine be free, and maybe we can turn around its sad reputation!

So many exceptionally beautiful clematis varieties are available in the trade today. By far the most popular group of hybrids is the Jackman clematis, botanically known as Clematis x jackmanii. This group of plants has members whose roots (so to speak) can be traced back to England in the mid-1800s. Various cultivars from this hardy group of plants produce flowers in pink, mauve, sky to deep blue, burgundy, red and white from mid- to late summer. Some cultivars bloom until frost, with vines reaching up to 15 feet.

A second group of clematis is the lanuginosa group. Generally, this group begins flowering in June and will last through summer. Some varieties will produce single blooms on new stems and double blooms on old wood. Dozens of cultivars are available with flowers of deep blue, crimson, pink or lavender.

The summer-flowering viticella clematis can climb to more than 10 feet. These hardy vines produce everything from wine red to small, rosy pink blooms in abundance. Two additional clematis groups, Florida and Patens, flower in rosy violet to deep lavender to bright blue, wine red and white. Many varieties have double blooms.

Generally, the various groups of clematis have the same requirements. They enjoy acidic soil from a pH of about 6, down to a pH of 4.5 or so. The old adage that advises us to keep their roots cool with mulch and their stems warm is certainly true. Be sure to plant your vine in a location that receives shade at some point in the day. Soil should be light, loamy and moist, but well-drained.

Diseases like leaf spot and stem rot often subject the clematis to stress. Borers, mites, whiteflies, scales and root-knot nematodes may attempt to destroy the vine as well. Damage from these diseases and insects can be minimized if attention is given to certain requirements.

For example, planting the vine in a location with optimal soil conditions will allow the clematis vigorous growth if disease is introduced. Additional practices such as thinning some individual stems away from the base of the plant will create better air movement through the mass of leaves and may also minimize the incidence of disease.

In spring, “to prune or not to prune?” is the question. And, as in many horticultural matters, there is no easy answer. The stems of the Jackman clematis and members of the viticella group can be cut back to within 4-6″ of the ground as the buds swell in spring. This pruning technique causes the plant to branch out, creating a larger framework on which flowers can flourish. Stems of the lanuginosa clematis can be trimmed back to 2-4 feet from the ground in spring, and will have the same effect. Dead or broken growth may be pruned from members of the Florida and Patens groups in spring. Otherwise, they should not be pruned until late summer when flowering is complete. Pruning back the old shoots in late summer will encourage bud break and vegetative growth, providing stems for next year’s blooms.

How do you know which group your clematis belongs to? If you haven’t saved the label that came with the vine when you purchased it, I’m afraid you may be destined to search the pages of a good plant manual in hopes that you find a plant description that matches the characteristics of your plant. Alternatively, you might take a clipping of your plant to a local nursery when it is in full bloom and ask them to identify it.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, RR1, Box 2120, Montville 04941, or e-mail them to dianagc@ctel.net. Selected questions will be answered in future columns. Include name, address and telephone number.