How to plant a clematis: depth, position and first prune

A clematis can live for decades, so the half-hour you spend planting it is well invested. Many of the problems people blame on the plant itself, from slow starts to sudden collapse, trace back to a dry, shallow hole tucked tight against a wall.

When to plant

The RHS recommends planting in spring or early to mid-autumn, when the soil is workable and moist. Container-grown plants bought in summer can go in too, as long as you plant promptly and keep them watered. Avoid frozen, waterlogged or bone-dry soil. The British Clematis Society notes that clematis can be planted whenever the soil is workable, but establish most easily in spring or autumn.

If you buy a small plant in a 7cm pot, the Society suggests potting it on into a 2–3 litre pot and growing it on first; larger plants can go straight out.

Choosing the spot

Clematis like their heads in the light and their roots cool and moist. Most need sun or partial shade, and evergreen and winter-flowering types want shelter from cold winds. Shade the base with low planting, a few flat stones or the shadow of a nearby shrub. If your only space is a shady wall, our guide to clematis for north-facing walls suggests suitable varieties.

Distance from walls and fences

Soil at the foot of a wall is often far drier than it looks, because the wall and any roof overhang cast a rain shadow. The RHS advises positioning the rootball 30–45cm away from the base of a wall or fence, further if there is guttering or an overhanging roof, and leading the stems back to the support along a cane. When planting into a tree or large shrub, it suggests at least 1.2m from the base, on the windward side, so that rain reaches the roots.

Preparing the hole

Clematis grow best in deep, fertile soil that holds moisture but drains freely. On heavy clay or thin sandy soil, dig in leaf mould or well-rotted manure before planting.

• Dig a hole at least twice the depth and width of the pot, as the British Clematis Society recommends.
• Fork over the bottom of the hole to break up compacted soil.
• Mix organic matter into the base; the Society suggests compost making up about a third of the hole's volume, with a little bone meal.
• Water the plant well in its pot beforehand. The Society suggests soaking the rootball for around 30 minutes.

How deep to plant

This is the step that sets clematis apart from most shrubs. Large-flowered hybrids are planted deeper than they sat in their pot, so that buds on the buried stems can produce new shoots if the top growth is damaged, whether by a careless boot, a slug or clematis wilt.

• Large-flowered hybrids (early and late summer flowering): the RHS advises setting the top of the rootball 5–7.5cm below soil level. The British Clematis Society goes further and suggests 10–15cm deeper than in the pot. Either is reasonable; on heavy, wet soil, err towards the shallower figure.
• Other types, including winter- and spring-flowering and evergreen clematis, late species such as C. viticella and C. tangutica, and herbaceous kinds: the RHS advises planting with the top of the rootball just below soil level.

Step by step

• Gently tease out any roots circling the rootball.
• Set the plant at the right depth, angled slightly towards its support if you are planting away from a wall.
• Backfill with the improved soil, firming gently as you go.
• Water thoroughly, let it drain, then water again.
• Keep the cane the plant came with and tie it to the support, so the stems can reach the trellis without kinking.
• Mulch with organic matter, keeping it a few centimetres clear of the stems.

Supports

Clematis climb by wrapping their leaf stalks around anything thin enough to grip, so they need wires, mesh or trellis rather than a bare wall. The RHS suggests fixing trellis or mesh on battens so it stands at least 2.5cm away from the wall, which lets air move behind and gives the leaf stalks room to twine. Tie young stems with soft twine in loose figure-of-eight loops; plastic twist-ties can cut into them.

The first prune

It feels brutal, but a hard first prune is the best way to get a bushy plant with several stems from the base, rather than one long, bare stem with flowers at the top. The RHS advises cutting all stems back to 15–30cm above ground, just above a bud: immediately if you plant in spring, or the following February or March if you plant in autumn. Once new shoots appear, pinching out the tips encourages further branching. The British Clematis Society offers a gentler option for plants that have not yet started growing: cut the existing growth back by about a third. After the first year, follow the routine for your plant's group, explained in our guide to clematis pruning groups.

Aftercare in the first year

New plants need regular watering through their first growing seasons. The British Clematis Society suggests watering at least once a month in the first year, and more often in hot, dry weather. The RHS recommends watering deeply, to about 30cm down, rather than giving frequent splashes; in the ground, that can take at least four watering cans per square metre.

Don't be alarmed if growth is modest in the first season. Clematis put much of their early energy into roots, and a plant that seems to sulk in year one often grows away strongly in its second or third.

Common planting mistakes

• Planting tight against a wall, where the soil is dust-dry.
• Leaving the rootball of a large-flowered hybrid at pot level.
• Letting a new plant dry out in its first summer.
• Skipping the first prune, which often leads to a single leggy stem.
• Using wire or plastic ties that strangle the stems.
• Planting into a sunny, exposed spot with nothing to shade the roots.