Clematis: how to plant, grow and prune these colourful garden climbers

Clematis are a mammoth group of climbers, which flower at different times of year and range from little patio plants to giants that flower through tall trees. Many people associate clematis with the large-flowered forms that bloom in early summer, but garden designers rarely use these today, and there is a wealth of other types, many of which have a more modern look and are easier to grow.

Of the 386 species, which hail from all corners of the globe, most are climbing plants. The name comes from the Greek klḗma, meaning tendril, as clematis twine themselves around support, such as shrub stems or trellis, to clamber upwards. There are also lesser-known non-twining herbaceous clematis, which will coat a small structure (such as an obelisk) if you tie them in.

Clematis vitalba, commonly known as old man's beard, is a vigorous native species that can be widely seen scrambling over hedgerows and trees in the countryside. It is most conspicuous during the cold months, when it coats plants in a mass of fluffy seedheads that glow silver in the sun. Most garden forms (with the exception of C. armandii and appropriately named C. montana) are less rampant.

The oldest garden variety is said to be the mouthful 'Purpurea Plena Elegans', whose dusky red-purple blooms resemble faded silk flowers from a vintage shop. It's a great plant and rivals cultivars introduced in recent years, such as fabulous spidery Rosalyn. Both are headache-free forms of the purple clematis (C. viticella), which is native to Greece, Iran, and Syria and was introduced here in the 16th century. Viticella varieties are easy to grow and bear small to medium flowers, which create a contemporary look. They are the obvious choice for most modern gardeners, but they are by no means the only option – there is a vast range available, and should you be (or become) a clematis fanatic, it is possible to have one in flower all year round because the 2,000 or so varieties bloom at different times.

Kicking off the show in April are the graceful flowers of Clematis macropetala and C. alpina. Opening in mostly soft shades of pink, blue, or white, the pretty blooms resemble bonnets or waterlilies and continue flowering into May. 'Albina Plena' and 'Blue Dancer' are two good choices. For bolder impact, opt for one of the dark pinks, such as 'Constance' or Octopus. Neither C. macropetala, nor C. alpina grow very big, making them ideal for a small garden. If it's size you want, C. armandii has long, glossy dark-green leaves and starry white or pastel-pink flowers that smell of honey and almonds; varieties such as 'Snowdrift' provide useful evergreen cover, but be warned that the plant is toxic to dogs and requires sheltered sun.

Clematis montana is a cottage-garden favourite, whose pink or white flowers release delicious vanilla-clove perfume from May into June; be careful which you buy if fragrance is important, as not all are strongly scented: pink 'Mayleen' is a safe bet, and the new white 'Silver Star' is said to have a great smell. In winter, the bronze or green leaves fall away to reveal an attractive tangled mass of stems, like a giant bird's nest. The montanas are big, so ideal if you have a garage or fence to clothe. Also flowering now are the traditional large-flowered forms (such as good old 'Nelly Moser') – they bloom in early summer and sometimes again in September; however, they can, arguably, make a garden look a bit dated and are often more susceptible to problems.

For a more contemporary look and an easy life, opt for forms of Clematis viticella, which produce small to medium-sized flowers from July to September; for instance, cherry-red 'Madame Julia Correvon' and blackcurrant 'Dark Eyes'. Texensis forms (such as vermilion 'Gravetye Beauty') flower at the same time, producing elegant cornets. Another long-flowering gem, the wonderful C. tangutica has bells that seem to have been carved out of lemon peel; 'Lambton Park' is a good variety, cheering the garden into October with coconut-scented lanterns, followed by silky seedheads that catch the sun. Also excellent for scent in late summer and early autumn are the pink-purple stars of C. x triternata 'Rubromarginata', which is vigorous, tolerant of tough sites, and fills the air with a perfume reminiscent of marzipan and hawthorn.

In a sheltered, sunny position, in milder parts of the country, forms of the semi-evergreen Clematis cirrhosa are a delight in the frosty months. 'Ourika Valley' has ivory bells and is one of the hardiest, and the blooms of 'Advent Bells' are speckled maroon.

Of the few herbaceous clematis, 'Arabella' is one of the best, bearing lavender-blue flowers over a long period in summer and early autumn, in sun or shade. She will scramble over the ground or coat a small obelisk in a pot, if tied in.

The rarely grown Clematis rehderiana (nodding virgin's bower) has dainty primrose bells that have a good scent and attract a lot of bees from midsummer, sometimes blooming into late autumn once the plant is well established. Flowering at around the same time, the copper and yellow lanterns of C. tangutica 'My Angel' are also great for providing late-season nectar. However, these are just two that provide for pollinators, and specialist clematis nursery Thorncroft has a range of bee-friendly recommendations on its website.

Birds (especially wrens) love the mad tangle of stems formed by montanas, such as 'Vera', and if you have one growing around your windows, you can watch them hopping about in it.

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Choose a site in sun or semi-shade that has very well-drained, retentive soil. Provide trellis or another structure for the tendrils to twine themselves around. Shrubs or trees that are not performing whilst the clematis is in flower can be used as climbing frames: for instance, a deciduous tree to show off a winter or early spring-flowering clematis or a lilac to show off a late summer or autumn-flowering clematis. Match the eventual size of the clematis to the size of the plant – for example, Clematis montana requires a large tree.

Water the clematis to be planted, before digging a hole a suitable distance from the wall, tree, or structure it is going to climb; for most clematis, this is 30 to 45 centimetres, but for a large specimen (such as C. montana) or for planting a normal-sized clematis next to a tree, 90 centimetres is better. Loosen the soil well and fork in peat-free compost (John Innes No. 3 is ideal), before planting the clematis at a 45° angle. The base of the stem (the level the plant had in the pot) ought to be 5 to 10 centimetres below soil level. Leave your supplier's cane in for support until the plant has attached itself to whatever structure you have provided for it to climb. Water in well.

The base of the plant should be shielded from strong sun, but the upper parts are happy to sunbathe. Ensure the roots are cool by having shrubs in front of the base of the clematis, by planting perennials around the base, or by mulching the base with woodchip or stone. Be patient – it can take a few years for a clematis to establish and put on its impressive show of flowers.

• Water young clematis regularly until established, especially in hot, dry weather.
• Feed once a year with a slow-release fertiliser (for instance, Osmocote) and fortnightly with potassium food (such as tomato feed) during the growing season until the plant flowers.
• Mulch with peat-free compost once a year.
• Protect from slugs, especially when plants are young or new growth is emerging.
• Tie in herbaceous types, which can't twine themselves around trellis as the climbers can.

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When: After flowering, in spring or early summer

How: This group doesn't need to be pruned; however, plants can be given a light haircut or thinning to keep them tidy. C. armandii dislikes significant pruning; however, large specimens of C. montana can be cut back if they become unruly: do it over a few years (for instance, trim one of the main stems down to 1.2 metres instead of cutting the whole thing back) to maintain flowering. Young plants differ and should be hard pruned straight after flowering in their first year.

When: Late winter or early spring and in midsummer after the first flush of flowers to encourage a second flowering.

How: Remove dead and unhealthy stems, and then prune healthy stems lightly, removing around one quarter to a third from the top. After flowering in midsummer, trim spent blooms.

Young plants differ and should be hard pruned in early March in their first year.

When: February or March

How: This group requires an easy, hard annual prune. In late winter or early spring, cut the whole plant down to around 45 centimetres above the ground, above a bud.

Protect clematis from slugs and snails, especially when the plant is young or new growth is emerging. Aphids and capsid bugs can also be a pain – remove fallen leaves from under the plant regularly and attract predators (such as birds). Large-flowered early summer clematis (not C. montana) are susceptible to wilt (in which the plant droops and blackens); if other types succumb, it is usually due to a lack of food or moisture. Powdery mildew can also take hold in drought or because of poor drainage or air flow. Slime flux (which is frothy, slimy, and smelly) can be caused by wind or frost damage and solved by cutting out the affected parts.