Clematis are one of the most popular flowering plants in English gardens. They have a reputation of being difficult - to grow well, and even to choose. With over 200 species and 400 cultivars it's easy to see why choice is hard! Here's my summary of how to choose and what to do. Choose a clematis that does what you want it to do
- Climbers: some grow up to 15m (50 feet), scrambling through trees and over buildings. Many are shorter, happily covering trellis, arches or arbours and no more.
- Herbaceous: short growing and ideal in a sunny border with perennials such as delphinium, phlox or any of the geranium family.
- Shrubs: from tiny and low growing to luscious 3m (10 foot) tall - clematis shrubs might surprise you.
Not sure how to find clematis to suit your needs? Use the RHS Plant Finder.
Choose a clematis that flowers when you want
- Early flowering clematis (pruning Group 1): flower in winter and early spring on shoots that grew from the parent plant in the previous year. Leaves may be evergreen, and flowers are single, bell shaped or open bell shaped, or saucer shaped. These are not huge flowers (up to 7cm / 3 inches). Their show-stopper quality is the sheer profusion of flowers early in the year.
- Early to mid season flowering clematis (pruning Group 2): flower in late spring and early summer on side shoots that grew from the parent plant in the previous year AND on the tops of shoots that grew in the spring. These clematis are deciduous and the flowers are upright, and mostly saucer shaped. Each bloom can be up to 15cm (6 inches) across.
- Late flowering clematis and herbaceous clematis (pruning Group 3): flower from summer into autumn on shoots that grow from the parent plant in the year when they flower. These are generally deciduous. Depending on the variety, flowers are large or small and any of a range of shapes.
Tackling problems with clematis
- Reduce the risk of clematis wilt. Plant the root ball of climbing species 8cm (3 inches) below the soil surface, in good soil that is rich in organic matter and well drained. Climbers will grow in sun or partial shade but their roots and the base of the plant must be in shade. So plant around them or cover the root ball with stones (beware slugs and snails).
- Create a perfect shape. Climbers need something to cling to – trellis, wire mesh or a tree are ideal. Grow herbaceous perennials in full sun, surrounded by twiggy sticks to support their growth. Prune at the right time and in the right place - read on!
- Prevent bare stems: on new plants, cut shoots back in the spring to 15-30 com (6 – 12 inches) from the ground, cutting just above a bud. Then, as new shoots grow, pinch out the tops once or twice (no more) to encourage side shoots. This may mean you don’t enjoy as many flowers in your first year as you will in future years.
- Feed your plants: add well rotted garden compost around the plant, but not touching the stems, in winter. And in spring, feed with a potassium rich fertilizer to encourage flowers.
- Deter voles, slugs and snails from eating tender new shoots - especially of group 3 species and varieties.
Pruning - this is the tricky bit!
The three groups of clematis described according to when they flower need three different approaches to pruning.
Group 1: immediately after flowering, prune to remove dead or damaged stems and to shorten others to keep the plant where you want it.
Group 2: before you see new shoots in spring, prune to remove dead or damaged shoots by cutting down to a strong bud. These buds will grow into a framework that supports spring growth of flowering shoots. Remove dead flower heads carefully because new shoots will bear flowers later in the summer.
Group 3: before you see new shoots in spring, prune the previous year’s growth back to a pair of strong buds on each of the stems at the base. Cut at about 20cm (8 inches) above the level of the soil.
The most important thing to do is choose a clematis that will do what you want it to do and prune it correctly. Read the labels and keep a note of the pruning group (1,2, or 3) to which your choices belong.
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