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Growing Clematis



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Larry Sagers Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved

Join me for Passionate About Perennials next month at Thanksgiving Gardens. Call 801 768 7443 for more information or log onto thanksgivingpoint,com and click on the education link.

If you like the beauty and practicality of flowering vines, look for showy spring blooming clematis. This genus is a member of the buttercup family and has more than 250 species and numerous garden hybrids. The word clematis is from a Greek word meaning "vine."

This genus includes many different plants that are mostly woody, deciduous climbing vines. Most varieties are cold hardy to USDA zone 3 so they survive throughout Utah. Some evergreen types are not cold hardy here and some are herbaceous and die back to the ground each winter.

Clematis show great variety in flower form, color, bloom season, foliage and plant height. The leaf stalks twine like tendrils and support the plants. Most varieties in Utah are a tangle of bare stems so they are not attractive during winter.

Look for three general flower forms: small, white flowers in loose, irregular spreading clusters; bell or urn-shaped flowers; and flat or open flowers. Some produce showy, ball-shaped or feathered fruits that are quite showy.

Clematis flowers are stunning. The large-flowered hybrid blooms range from four to ten inches in diameter and can produce as many as 100 blooms per plant each season. The species types blooms range from one-half to three inches in diameter and have many diverse shapes and habits. Many species clematis have fragrant blooms, but most hybrids do not.

Clematis were insignificant nursery plants until breeders developed hybrids in the 1850s. Breeders crossed Oriental and European species in Europe until the 1890s. This was the “Golden Age of Clematis” and they introduced more new varieties than any other time in history.

Many popular varieties grown today originated then. Britain’s leading hybridizer in the 1860s was the Jackman Nursery, and in 1862 they introduced Clematis x jackmanii that is still the most popular variety clematis grown today. Although interest waned in hybrids, there is renewed interest in very hardy and disease-resistant small-flowered clematis types.

Some complain clematis are difficult, but select the right site and give them good care and they will thrive. They prefer six hours of full sun but need some protection during the heat of the day. The plant's stems and foliage need sun, but keep the roots in a cool, moist environment. The plants love mulch so add at least two inches each year.

The real mystery of growing clematis is learning how to prune the vines. The mystery comes because not all clematis are pruned the same. There are three major groups depending on the time of year the plants flowers.

Prune the vines each year so plants produce the maximum number of flowers. Plants still grow and flower without pruning but the flowers are usually not where you want them.

The earliest flowering clematis need no new growth for plants to bloom, but the later flowering types must have new growth for flower buds to form. Some types may cross lines. Clematis vines become entangled so make cuts carefully then spread and train the vines to cover the maximum possible area. This displays the blooms for their maximum effect.

Sometimes older, neglected plants can be cut back into older wood and new buds may break. Growth from old wood is likely to be weak and slow. If no pruning is done, flowering still occurs high in the plant and out of sight.

The early-flowering clematis bloom in April and May, from buds produced the previous year. Prune these after they bloom before the end of July. This allows new flower buds to grow for the next season. Remove shoots that bloomed previously and prune vines to reduce the size or make a good branch framework. Do not cut into the woody trunks. Plants in this group include: C. alpina, C. macropetala, C. armandii, C. montana and C. chrysocoma.

Large-flowered hybrids bloom in mid-June on short stems from the previous season's growth and often rebloom with smaller flowers in late summer on new growth. Remove dead and weak stems in February or March and then cut back remaining stems to the topmost pair of large, plump green buds. This cut could be a few inches to a foot or two from the stem tips.

These plants often become bare at the base as they mature. Underplant them to help conceal the stems. You can often force a flush of new growth from the base by cutting the vine back to 18 inches immediately after the flush of bloom in June. Plants in this group include: 'Nelly Moser,' 'Miss Bateman,' 'Lasurstern,' 'Duchess of Edinburgh,' 'Mrs. Cholmondeley' and others.

Late-flowering clematis flower on the last two to three feet of this season's growth. Some types begin blooming in mid-June and continue into fall. This group is easiest to prune since you do not need to maintain old growth. Cut each stem two to three feet long in February or March. This removes some good stems and buds but the plant still blooms well.

Eventually the length of the bare stem at the base will increase as the vine matures. Plants in this group include: C. viticella, C. flammula, C. tangutica, C. x jackmanii, C. maximowicziana, 'Perle d'Azur,' 'Royal Velours,' 'Duchess of Albany' and others.

Look for many favorite clematis at local nurseries right now. Some native species thrive in our area and even flourish as low water use plants. Make this season the one to add some of these beautiful plants to your garden.

For a listing of selected species and cultivars and how each of the categories need to be pruned, check my website at www.larrysagers.com

Check for the latest updates on when to spray your fruit trees and what products to use at http://extension.usu.edu/cooperative/ipm/.

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