Date: June 15th, 2011
Clematis come in a wide variety of flower forms and colors. They can be divided into three groups based on habit and time of flowering. The first and second groups bloom on the previous season's wood while the third group blooms on new wood.
The first group are the early-flowering evergreen species which are suitable for warmer climates that lack severe cold. They require very little, if any, pruning. Cut them back hard when they are first planted.
The second group are the early, large flowered varieties that are much hardier. They are ideal for container plantings or for growing through an already wall-trained tree or large shrub where the leaves of the host plant can protect the blossoms from wind and rain. Lighter colored flower varieties should be planted in shadier locations and the darker flowered varieties should be planted in more sunny locations. Prune group two clematis in early spring before new growth begins.
The third clematis group contains the late-flowering cultivars, both large and small-flowered. Climbers like 'Jackmanii' are in this group as well as the lower growing herbaceous and ground-cover varieties, many of which have striking seed heads after flowering which provide added interest. This group should be pruned in early spring before new growth commences.
Most climbing species of clematis prefer sun to part shade. Herbaceous varieties prefer sun. Make sure that the roots are kept cool and shaded. This can be accomplished by under planting them with low-growing evergreens. Clematis grow well in fertile soil that is rich and well-drained. The pH should be kept neutral or slightly alkaline for best results. To keep soil at a healthy pH, use an Electronic Soil Test Kit. This test kit helps to alleviate over and under fertilizing and will check pH and nutrient levels of your soil in no time.
Plant clematis 2 inches deeper than the soil surface of the pot the plant arrived in. This helps buds develop below soil level and aids in disease resistance. Do not situate clematis in locations that remain wet in the winter months as this can cause the thin fibrous root systems to rot very quickly.
For patio plantings in containers, choose a container that is at least 18 inches across and 18 inches deep.
Water new plants well until they are firmly established. Provide mulch of well-cured manure or compost for the climbing and herbaceous cultivars in early spring each year.
In early spring, new growth is very prone to damage by slugs. Clematis may also suffer from aphids and powdery mildew. Freshly planted large-flowered varieties may also contract a fungus known as Clematis Wilt. However, a product such as Wilt Pruf has proved effective in stopping the fungus.
Clematis must be trained to their supports. Make sure that the support you have chosen is sturdy enough to support the weight of a mature plant heavily laden with blooms. If your support is a host plant, make sure that the rates of growth are compatible, otherwise the host may become overwhelmed and die. Tie new growth just below leaf axil buds to the support in spring and summer. Space the stems evenly, leaving room for new stems to grow. Prune all new plants hard the first spring after planting unless the plant already has more than three stems. This will avoid excessively long stems which leave the plant bare at the base.