Clematis, Beautiful climbers.

Philadelphia Flower Show
Clematis lecture by Raymond Evison
March 2004

Clematis

Background information on Raymond Evison, the speaker and author of two books on Clematis.

Mr. Evison, author of The Gardener's Guide to Growing Clematis (Timber Press) and Clematis for Everyone (Floramedia), shared his knowledge in an overview about growing clematis in the northeast United States.

He heads a nursery in Guernsey, England, which grows only clematis. Guernsey is in the Channel islands, 100 miles south of England and very close to France. It has a craggy coast line. Guernsey has few frosts and cool summers, making it is a very good place to raise clematis. His company has 600 species and cultivars of clematis. They also make sure that the old cultivars don't get lost. Each year his company grows four million clematis plants. They have about 8 and 1/2 acres under glass and a mechanized system to be competitive in the world market. It takes about 9 or 10 years of trials after seedling development before selling new clematis commercially. In October his staff makes about 40 to 50 thousand cuttings. They use old fashioned methods using gravel on top to avoid killing off. After three weeks the cutting takes root. To water they use an ebb and flow system, putting water underneath. They recycle water and use night screens too. The nursery exhibits at clematis at the Chelsea flower show, the largest outside show in the world as well as at the Philadelphia Flower Show.

His main focus is to grow healthier plants, good reds and blues, and a buttercup yellow.

Clematis Lecture

History

Clematis is found native from the United States to China and Tibet. Some grow 50 feet high, others are ground covers. European collectors brought plants and seeds to Europe in the 1850s onward. Large-flowered cultivars appeared . The majority of species grown in Europe and North America are natives of the Northern Hemisphere. Experts speculate that early large-flowered cultivars were derived from C. Patens, native to northern China and Korea, then naturalized in Japan. Since 1860, large-flowered cultivars also have originated in Europe and North America.

Types

There are about 200 recorded species and upward of 1000 cultivars of Clematis. Roots of some are fine and fibrous (like C. Macropedula or C. Alpina) making re-rooting established plants very, very difficult, while others, such as C. Florida and C. Viticella have larger fleshier roots.

Clematis belong to the Ranunclaceae family. Other members of that family are the buttercup (Ranunculus), Kingcups (Caltha), and columbines (Aquilegtia), delphiniums and hellebores.

There are different types of clematis. They can be grown in various ways, such as associating the vine with other plant material, as a ground cover, or grown in containers. Certainly in Victorian times they grew clematis on trellis in containers. They also work well climbing through trees, pines, and roses. Some types can be used as ground covers, as well.

William Kennett, a variety available in 1875, is still good; so don't discount older varieties.

There are three pruning groups. These groups reflect, for the most part, the hardiness and blooming period of the plant. One type is the species patens, which belongs to the Section Viticella, with the sub section, Patens. Flowers are produced between late spring to early summer. Some have repeat bloom in late summer to early autumn. Examples are Nelly Moser and Anna Louise.

Mid-season are the large-flowered cultivars derived from the section C.Viticella, subsection Lanuginosa. They bear solitary flowers from the leaf axial buds ripened on the previous year's wood. And they continue to produce new growth after the flowers; then bear further crops of flowers again in fall.

Late large-flowering crosses of c. Lanuginosa and C. Viticella flower on this year's new growth, and are hardy in zones 3 through 9. C. Jackmani and C. Comtesse de Bouchard are examples of this later flowering category. These clematis could be cut back each spring, and still flower that year.

Clematis in America

Clematis will grow in the United States and in northern climates; just choose the variety carefully. There are native clematis varieties from the Appalachian Mountains to Texas. Clematis often has an early large flower, followed by an interesting seed head. The flowers can be cut, and the seed heads dried for winter decoration.

Some types work as ground cover. Some will grow well in any climate; Polish Spirit will grow for anyone, anywhere.

Clematis are categorized into three different groups depending on when they bloom and if they bloom from previous year's wood or if the cultivar only blooms on the new growth. This is important to know if and when you prune the cultivar (so pay close attention to the label on the plant).

The first group are those which will bloom in early spring or summer, from old wood. For those, don’t prune until after blooming. There are the Nelly Moser types. There are those which bloom only on new wood. For the later flowering types you can cut back in March to 12 inches (at least the first year). Pruning group three are the Jackmani types.

But to remember, when to prune, use the old saying:
If your clematis blooms before June, don't prune.

Where to plant clematis

No matter where you plant a clematis, it will take time to become established (sometimes five years or more). Once established they will bloom profusely.

Due to heat and dryness, clematis doesn't do well on south facing wall. Clematis plants do like a micro climate with other plant material. They like their heads in the sun and their feet (roots in the shade)—so mulch if you feel they might be getting too much sun. Or plant them in a shady area that permits the vine to grow to the sun. If you mulch, make sure to keep the mulch away from the stems about two to four inches to avoid stem rot.

Herbaceous clematis plants do work well in a mixed border. Petifola tolerates the heat. And can be planted to cover low shrubs. Also, some do not grow higher than three feet. Clematis also work as mixed border plants. Mauve flower, Chinook; Savannah (pink), Gracifolia, var. gracifolia, which is white and fragrant; Victor Hugo a mauve.

Clematis vary in hardiness and in time of bloom, depending on climate and conditions. So read the labels on clematis before buying—or check books for details on growing a particular cultivar. For example, Paniculata is a New Zealand plant. It is early spring flowering in Oregon but not winter hearty here in the North East. In the North West they are evergreen. C.C. Freckles likes a Mediterranean climate. It has summer dormancy in North West United States. It then flowers in the fall in a mild climate. In severe climates such as here, grow winter hardy types. C.Alpina has masses of seed heads, C. Macropedula, which comes from northwest of Beijing (Peking), China does well on a north facing wall, or exposed wall, and will flower well. They will put up with nasty winds and cold. Macropedula Markums’ Pink can grow to 10 feet. It has flowers in late spring or early summer, then sets lovely seed heads. C. Alpina Frankie, has an inner skirt, pink flamingo a double type, flowering in early may and sets lots of seed heads. Montanas will cover buildings, but do not survive under 5 degrees F. It also doesn't survive in a wet soil. Elizabeth has a wonderful vanilla scent, but doesn’t do well in the North East as it would not be hardy there. It can cover 3 ft walls, a really strong fence or out buildings. It can grow in pines as well.

Container plants

If you can’t grow a particular clematis variety in your area, consider planting it as a container plant. You can take the pot inside during harsh weather. The planting depth should be 18 inches. Don't be skimpy with the soil and add plenty of nutrients. A thick walled container is needed. Don't use a plastic container as it will heat up during the summer. Lift the container off the ground. It also may not survive the winter if the container is left outside. Use summer bedding plants to protect the roots. Will Goodwin is good in containers; it has a light blue, a nice flower.

Try putting varieties from the same pruning group together, so they can be pruned together. An example are Dr. Rupple, and Gipsy Queen. Pruning group two works best for containers (check books for lists of pruning group varieties). Use a half barrel as a container, and use bamboo canes for a trellis in the barrel. C. Anna Louise is ideal for containers. Blue Moon, now called Clair de Lune, wound work in the south. Royal Velvet, too. All are good for late May early June with a few fall flowers. C. Alabast has creamy green flowers, this can work in a north facing wall. C. Sugar Candy, a newer one, has 7 or more inches of flower. Pale flowers best grow in shady or a north area.

Double flowers: A regal collection

Arctic queen, a double white, is ideal in a container. Josephine, a pink, is a double and free flowering. It is also a good garden plant. Crystal Fountain, exotic flowers, double. Gipsy Queen and Star of India are also lovely flowers.

Fertilizer

Rose feed works well for them. Mulch and fish fertilizer also is helpful. Clematis plants are heavy feeders. Clematis plants work well with roses. Later flowering types include the Jackmani types.

When to Plant?

It is best to plant in the autumn.

How to Plant?

Put good compost in the hole. Plant 2 inches deeper than it was planted in the container, so it will re-grow if it experiences wilt. (Copper-based fungicide will kill the wilt.)

Pruning clematis

The spring after you plant, cut the plant down to 12 inches to make it bushy from base. You will lose the flowers for that year, although some might appear in the fall. But in the long run, you will have a healthier and sturdier plant.

Once again, use the old saying:

If your clematis blooms before June, don't prune.

Links to Clematis information