Growing

Introduction

Most people consider clematis to be climbing plants with large flowers, that are quite complicated to prune. This could not be further from the truth. Clematis occur in many forms depending on the variety, from plants hybridised by humans to numerous wild species. Some climb by clinging to their host, some scramble and do not cling, whilst some herbaceous ones form twiggy or bushy clumps. Certain clematis flower in spring and some repeat in summer or autumn. Some flower from summer onwards, whilst others bloom in winter. Clematis flowers vary in both size and shape, from the large-flowered summer hybrids to the smaller spring or autumn varieties, some of which are scented.

Choosing a clematis – some things to consider

Where do you want to plant it? What do you want it to do in your garden – cover an unsightly oil tank or climb up a small host without damaging it? Do you want it to flower before or after its host, or at the same time? Clematis have varying growth habits, from under 1m to over 10m, but much will depend on moisture, nutrients, shade levels, and quality of the soil. There is also a group of evergreen clematis that keep their leaves over winter and shed a few at a time throughout the following seasons. Some clematis are even suitable for growing in containers.

Buying a clematis

Clematis are offered for sale in varying sized pots. Small rooted cuttings in 7cm pots, sometimes in multiples of 3–4 for £10, may sound like a bargain but do not plant these babies in the garden or into large containers when you get them home. Pot them on into 2- or 3-litre pots and wait for them to grow much bigger root systems capable of competing with more-established garden plants. If you want to plant out clematis immediately, buy them in 3-litre pots. Whilst these can be planted out whenever the soil is workable, they will establish more easily in either spring or autumn.

Plant labels

A clematis from a good source will have a plant label that carries important information about name, type, eventual height, aspect (sun or shade), flowering time, size of bloom, when and how to prune, etc. Be aware, however, that plastic labels fade in bright sunlight and therefore the picture of the flower may not be a true colour likeness.

Planting a clematis

Having bought your plant, you must give it a good home and a lot of attention, at least for the first year. Dig a hole at least twice the depth and width of the existing pot. Suitable compost (about a third of the volume of the dug hole) should be mixed with bone meal and placed at the bottom. Large-flowered clematis should be planted 10–15 cm deeper than they were in the pot, whilst all other clematis can be planted at the same depth as they were in the pot. Tease out the root ball before plunging it in water for 30 minutes, then plant it and back-fill the hole, gently firming the soil as you go.

Secure the plant to a suitable support and prune the existing growth by a third if it has not yet started to grow away. By doing this you will encourage more side shoots, which will produce more stems and flowers on a bushier plant. Now give your plant another watering. For the first year make sure the new plant does not dry out by giving it a good watering at least once a month, and more often in hot and dry conditions.

Clematis in containers

Clematis like moisture passing through their roots but don’t like standing in static waterlogged containers. Use a deep container, at least 46cm in diameter, and with one with the thickest walls your purse will allow. This will help to keep the compost cool in summer and less cold in winter. If plastic pots are used, then line the inside with bubble wrap or polystyrene to insulate the compost from the outside temperature. Excellent drainage is essential. Use broken crocks at the bottom of the pot to ensure the drainage hole does not become blocked. The more drainage holes there are in the pot the better.

A soil-based compost such as John Innes No 3 with added grit would be ideal. Non-peat-based mediums can also be used but tend to dry out more easily and don’t give the container the same degree of ballast. Large-flowered clematis are greedy feeders so applications of high-potash liquid fertiliser at half-strength fortnightly during the growing season will maintain healthy top growth. Smaller-flowered clematis need less feeding.

Pruning

When to prune will be set out on the label. Generally, plants flowering in early summer (before end of June in the northern hemisphere) will only require a haircut of the dead vines, working from the top downwards to where live buds are apparent. Late-flowering plants require a hard prune of all top growth. Prune all main stems about 15cm from ground level and take all growth away. When these start into growth, pinch out the growing tips after two pairs of leaves, to make a bushier plant. Herbaceous woody varieties can be pruned in late autumn to about 15cm from ground level.