How To Grow Clematis

Clematis_in_gardenClematis must surely be one of the best climbing plants we could wish to grow. The diverse flower forms in numerous colours and shades, make these gorgeous climbers are one of the most popular plants grown in Britain today.

Clematis are not just summer flowers, they have early flowering varieties, mid season and late flowering types, so if you want to have flowers almost all year round, by selecting the appropriate varieties you can have blooms for a good part of the year. The clematis is a member of the buttercup family. 

This genus includes approximately 250 species and numerous garden hybrids. It is a varied genus, made up of mostly woody, deciduous climbing plants, though a few are evergreen and a few herbaceous. Clematises are hardy plants and can survive for 25 years or more. Leaves are opposite on the stem and mostly compound with three to five leaflets. The leaf stalk twines like a tendril and is responsible for giving the plant support. The flowers are showy, having four (sometimes five to eight) petal-like sepals (no true petals).

There are three general flower forms: small flowers in panicles or loose and irregular spreading clusters; bell or urn-shaped flowers; and flat or open flowers. The large-flowered hybrids may have blooms ranging from 4 to 10 inch. (10cm-25cm) in diameter and as many as 100 blooms per plant in a season. The species types have blooms ranging from 1 ½ in.-3in. (38mm-76mm) diameter with diverse shapes and habit; some of the species have fragrant blooms, which is not true of most hybrids. 

ANNUAL CLEMATIS MAINTENANCE: Once the plant is well established, some basic care is needed on an annual basis. In dry seasons, watering deeply once a week is recommended. Renew mulch to a two-inch depth in late spring after the soil has warmed unless a groundcover plant or other method is used to cool the root environment. All most every fertilizer contains three main ingredients: nitrogen (N), phosphorus or phosphate (P) and potash (K). Nitrogen encourages leafy growth and is a key element, because healthy foliage is essential for overall healthy plant. Phosphate is especially valuable in encouraging root development and so is very useful at planting time to aid initial establishment. Potash plays an important part in promoting flowering and fruiting, especially significant with a flowering ornamental like the clematis. Most blended fertilizers also contain other minor nutrients like magnesium, calcium and boron.

One very important element we haven't mention yet is iron, which helps in the process by which the green colouring matter, chlorophyll, is manufactured. Use a fertilizer containing sequestered iron; good commercially prepared fertilizers will contain this vital ingredient. When planting, use a fertilizer with a high phosphate content; bone meal, applied, as a good handful to the planting hole is ideal. Each spring give the plant a handful of a proprietary rose fertilizer. During the summer when the plant is growing rapidly, a general-purpose liquid feed such as the type used for tomatoes can be given.

Plants will need about one inch of water per week during the growing season applied through irrigation or rainfall. To maintain the soil around the established clematis in a moist condition, mulch around the roots making sure that the soil is wet thoroughly before the mulch is added.

CLEMATIS PROPAGATION: Success propagating clematis by cuttings or layering can have something of a mixed success rating depending on experience. Cuttings taken in May or June from half-hardened shoots of the current season's growth can increase all types of clematis. Use a rooting mix of two parts sand and one part peat and a rooting hormone (available at garden centres). Supply high humidity, warmth and light in order for the cuttings to root within four to five weeks. The large-flowered hybrids will take a little longer to root; if cuttings are taken in May, they may not root until late August. If rooted by early August, plant them out. If no rooting occurs until late August, hold plants over winter in pots and plant in early spring.

Layering is the easier method and can be done in early autumn. Choose a mature stem produced earlier in the season, or from the previous season's growth. Secure it into the soil at the nodes or bury a pot containing a mixture of equal parts sand and peat and secure the stem into this. Rooting occurs within about 12 months at which point the rooted sections can be detached and re-planted.

CLEMATIS PROBLEMS: The most devastating condition of clematis is a fungal stem rot and leaf spot caused by the fungus Ascochyta clematidina and commonly called "wilt." This is a disease found generally on large-flowered hybrids. Small-flowered hybrids and the species and their cultivars are less susceptible to wilt. Symptoms include a sudden stem collapse generally just as the flower buds are about to open, and within a few days, the stem and leaves turn black. Any part of the plant can be attacked down to and just below the soil level. The usual treatment is to remove the diseased stem below the wilted section, even below soil line.

Plants usually recover from buds lower on the stem. Powdery mildew is another fungal disease that can occur on flowers and young stems, usually in July and August. It should be treated with a fungicide when first noticed as the fungus can disfigure leaves and flower buds, causing them not to open.

CLEMATIS HISTORY: There was very little interest in clematis until the 1850s when many were crossed and improved. Plants from Japan and China became the parents of many hybrids. Breeders in Britain, France, Belgium and Germany were responsible for many of the varieties bred during the period of the 1890s; in fact, more new varieties were introduced during this period than any other in history and many clematis grown today originated then.

The leading hybridiser in Britain in the 1860s was the Jackman Nursery, which produced C. x jackmanii (introduced in 1862), still the most popular clematis grown today. In the 1880s, interest in clematis waned; Hybridisers were running out of ideas and the wilt "epidemic" put a damper on cultivation. Today, there is renewed interest in clematis, particularly in very hardy and disease-resistant small-flowered types.

CLEMATIS CULTIVATION: Clematis have a reputation for being difficult to grow, however, like any other plant, if their needs can be met by the site and proper care, they will thrive. Clematis requires full sun to grow best though some dappled shade during the heat of the day is beneficial. Flowers of some red and blue large-flowered hybrids and the ones with delicately pale flowers, fade badly if they get too much direct sun. Those are better planted in eastern exposures or partial shade. The site should be open enough to allow for air movement around the plants.

Soil should be rich and well draining with a pH close to neutral (7.0). Though the plant's stems and foliage should be in sun, the roots like a cool, moist environment. With the exception of C. montana, clematis do not compete well with large tree roots. Most clematis will require staking so the twining leaf petioles can cling and climb upward, though some gardeners choose to let the plants sprawl over the ground, low walls, other plants, etc.

TRANSPLANTING CLEMATIS: If you need to transplant your clematis then it should be transplanted in autumn, late winter or very early in spring before growth begins. Dig as large a root ball as is possible (make sure soil is moist); the more roots preserved, the less the transplanting process will stress the plant.

PRUNING CLEMATIS: The main purpose in pruning is to help plants produce the maximum number of flowers and at the height, which they can be enjoyed, so annual pruning is recommended. Sometimes older, neglected plants can be cut back into older wood and new buds may break. Growth from old wood will likely be weak and slow. If the plants are not pruned at all, they would still grow and flower but the blooms would be well above the ground, in many situations they might even be well out of sight. Not all clematis can be pruned in the same way. There are three methods that can be applied to major groups depending on the time of year the plant flowers. Some clematis flower on the previous years wood, those are the earliest flowering varieties, but the later flowering types must make new growth in order for flower buds to form. A few plants are not strictly bound to the following groups but may cross lines. Because vines will likely be entangled, make cuts carefully among the intertwining vines and spread and train them in various directions in order to cover the maximum possible area. This enables the plant to display its blooms rather than be bunched up. Training shoots horizontally not only keeps the flowers within eye level, but also provides better coverage of the support, and the reduced flow of sap encourages more flowers.


GROUP A: Early-flowering Clematis Plants in this group bloom in early spring, generally in April and May, from buds produced the previous season. Prune these back as soon as possible after bloom but no later than the end of July. This allows time for new growth to produce flower buds for the next season. Remove shoots that have bloomed. You can prune out more stems to reduce the size of your plant if it has become untidy, or to form a good framework of branches. Do not cut into woody trunks. Plants in this group include: C. alpina, C. macropetala, C. armandii, C. montana and C. chrysocoma.
alpina 'Frances Rivis'

GROUP B: Large flowered hybrids bloom in mid-June on short stems from the previous season's growth and often again in late summer on new growth (these blooms are smaller). Prune in February or March by removing dead and weak stems, 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. You may be able to force a flush of new growth from the base by cutting the stem back to 18 in. (45cm) immediately after the flush of bloom in June. Plants in this group include: 'Nelly Moser,' 'Miss Bateman,' 'General Sikorski', 'Duchess of Edinburgh,' 'Lawsoniana', 'Mrs. Cholmondeley'.

GROUP C: Late-flowering Clematis. Plants in this group flower on the last 2 -3 ft. (60cm-90cm) of the current season's growth. Some types begin blooming in mid-June and continue into the autumn. This is the easiest group to prune since no old wood needs to be maintained. In February or March cut each stem to a height of about two to three feet. This will include removal of some good stems and buds. Eventually the length of the bare stem at the base will increase as the vine matures. Plants in this group include: C. campaniflora, C. viticella, C. flammula, C. tangutica, C. x jackmanii, C. maximowicziana, 'Perle d'Azur,' 'Royal Velours,' 'Duchess of Albany' 'Alba Luxurians'.

CHOOSING CLEMATIS PLANTS: Plants are available in garden centres and nurseries, though one good way of choosing your plants is on-line through one of the specialist suppliers. The species and small-flowered hybrids have fibrous roots that are susceptible to root damage; disturb roots as little as possible. Select plants that have multiple stems, healthy, dark green growth and a root system that fills the container.

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