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Home & garden.

Updated: 6 Dec 2021

How to grow clematis

Clematis are one of the most popular climbing plants. Discover our best clematis varieties and tips for how to grow them.
Ceri Thomas
Pink clematis

You can grow clematis in the ground or in containers, and by planting varieties from the diverse groups that flower at different times of the year, you could be enjoying the delights of clematis for many months. 

Which? Gardening magazine grew a range of popular varieties to see which would give us the best display throughout the year.

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Key facts

PLANT TYPE Hardy climber 

POSITION Sun or partial shade with shaded roots

SOIL Well-drained and fertile

How to grow clematis: month by month





Best clematis varieties

Which? members can log in now to see the full results and which are our Best Buy varieties. If you're not a member, join Which? to get instant access.

Best Buy spring-flowering clematis
What it looks likeVariety nameHeight x spread
120 x 140cm
This variety is part of the Forsteri group of clematis and is a scrambling, evergreen plant. Its long stems and attractive, shiny, dark-green leaves form a dense and quite large mound. When the flowers open, it transforms from a rather untidy specimen into a firm favourite. The mass of creamy white, cup-shaped flowers cover the plants, forming an impressive display that really stands out. Grow with C. x cartmanii ‘Avalanche’ or ‘Joe’ to get seedheads
What it looks likeVariety nameHeight x spread
300 x 70cm
This variety has slightly twisted, violet-blue outer sepals over a bell-shaped cream centre that creates flashes of light through the blue. The colour stands out against the soft, dark foliage. Peak flowering only lasted a few weeks in our trial, but was followed soon after by a second flush of smaller flowers and then the occasional bloom through to the end of September. It also holds an RHS Award of Garden Merit (AGM).
Best Buy early to mid-summer flowering clematis
What it looks likeVariety nameHeight x spread
210 x 175cm
A variety with real presence, thanks to its strong growth and the intense colour of the flowers. In our trial, we found that by mid-June it had a dense canopy of foliage, which created a backdrop for the plate-like blooms. Each petal is dark-red with a wide central bar of deep pink; the golden stamens provide a good contrast. July sees seedheads and more flowerbuds, the latter heralding a second flower display at the end of August. Pruning group two.
What it looks likeVariety nameHeight x spread
200 x 115cm
In two separate trials, we’ve found this compact variety equally good for growing in a pot or the ground. Its mauve flowers, with a pronounced silvery bar, a thick ruff of lilac stamens that resemble rolled petals and bright, yellow-green centres, have an exotic look. Equally impressive is that it is capable of nine weeks of flowering in two main flushes in early and mid-summer with a few sporadic blooms in between. Pruning group two.
What it looks likeVariety nameHeight x spread
Best Buy mid- to late-summer flowering clematis
What it looks likeVariety nameHeight x spread
250 x 75cm
This clematis has delicate leaves and flowers with an absolute profusion of small, deep violet-purple blooms with contrasting cream stamens that make a hugely colourful display. A worthy Best Buy, it’s been awarded an RHS AGM, too. It can reach five metres in height and when we grew it, it coped well with a cold spring and very hot summer. The first flush of flowers were quickly followed by fresh blooms and flowering lasting a total of 13 weeks. Pruning group three.
What it looks likeVariety nameHeight x spread
250 x 50cm
The large flowers of this variety have bright yellow stamens that stand out against the dark-pink, slightly ruffled sepals and give a beautiful display, even as they age and fade to a lovely plum colour. In our trial, this variety was undaunted by hot weather, producing a succession of buds and blooms, which lasted for 17 weeks from late May to the end of September. The plants are tall but slender and would suit a tall obelisk or arch. Pruning group three.
What it looks likeVariety nameHeight x spread
Best Buy patio clematis for growing in a pot
What it looks likeVariety nameHeight x spread
120 x 70cm
The gorgeous cobalt blue of these very large flowers really stood out in our trial. Even when they faded to a more washed-out pinky blue, they still looked lovely. The sheer flower power was also outstanding: our plants were almost completely cloaked in vibrant blooms at their peak. Bushy plants, which didn’t attempt a getaway, and silky, spidery seedheads also added to their charms. This is a fabulous plant from all angles.
What it looks likeVariety nameHeight x spread
150 x 70cm
The large and remarkable double flowers were arranged in two layers, with the flat violet-blue petals below and paler quilled petals above. Our plants were bushy with a neat shape that they kept all season, making them ideal for pots. Blooms opened from the top to the bottom of the red stems, too, so we got a really good covering of flowers, and they managed three full flushes in one season.
What it looks likeVariety nameHeight x spread

How we test clematis

We grow different varieties alongside each other so we can compare them as they grow. We assess the weekly through the growing season so we can see how they perform. We grow them for two years to see how well they do through winter as well as summer.

Caring for your plants


Preferably buy plants in 2-3L pots and plant at any time of year when the ground is workable, although the dry summer months aren’t ideal. Provide shade for the roots so they stay cool. Plant them so the rootball is 5-7.5cm under the soil so that buds underground can regrow if the top growth gets damaged or diseased and has to be cut back. Water regularly for several months after planting until they’re well established.

Feeding and watering

In fertile soil they may not need feeding. In poor soil use a general fertiliser, such as Growmore, in spring. Mulch annually with 5-7.5cm of well-rotted compost. Established clematis shouldn’t need watering unless the soil is very dry.


Group one Trim back after flowering and tie in stems as needed. Cut back by around half to renovate if needed.

Group two Dead or weak stems can be removed or shortened before flowering in February or March. After flowering, some stems can be cut back by half to side-shoots or strong buds to encourage new growth and a second flush.

Group three In February or March, cut all stems to a pair of healthy buds around 20-30cm from the ground.

Growing clematis in a pot

  • Use a large pot to give roots room to grow; roughly 45cm in diameter and depth.
  • Use a Best Buy compost for containers and mix in a Best Buy controlled-release feed.
  • Avoid clematis wilt by planting deeply so the top of the roots are below soil level.
  • Buy a good-quality obelisk that will support your plant for a number of years; we found that cheap wicker obelisks soon broke. Ensure the diameter will fit your pot.
  • Topdress with fresh compost and controlled-release feed annually.
  • Water regularly; daily during hot weather. 
  • Most varieties will grow better if you site them away from potential cold winds. Strong sun can fade flower colours. Move the pot so the plant gets some midday shade if necessary.

Common growing problems


Greenfly can quickly build up and cause poor growth by sucking the plant’s sap. Treat by squishing any colonies by hand.

Read more about greenfly.

Clematis wilt

This is a fungal disease that causes the whole plant to wilt. Planting deeply will mean that you can cut back the whole plant and it should regrow from the base. Sometimes the cause isn't clematis wilt but actually physical damage such as slugs nibbling the stems at the base.

Green petal

Green petal is caused by cold spring weather while flowerbuds are forming. Some petals become bright green and distorted, but there are no detrimental effects to the plant. 

Read more about green petal.

Slime flux

This is a bacterial problem that can cause the plant to collapse and horrible ooze to come out of the base. Cut back the whole plant and it should resprout from the base.