How to grow clematis
One of the most popular garden plants, clematis produce masses of flowers in a variety of shapes and colours. From vigorous to compact climbers, as well as herbaceous types for a sunny border, here’s everything you need to know to grow these plants in your garden.
- Easy to grow and many to choose from
- With careful selection, it’s possible to have flowers throughout the year
- Plant in spring or early- to mid-autumn
- Cultivars available to suit any aspect
- Prune annually according to flowering time
- Climbing types need their roots kept cool and moist
- Make new plants by cuttings, layering or by seed
All you need to know
Being one of the most popular garden plants, there are many different species and cultivars to choose from. To pick one that's right for your garden, consider the following:
Size and habit
Firstly consider if you want a climbing plant, perhaps for a wall, fence, pergola or obelisk, or are you looking for a non-climbing herbaceous clematis to grow in a mixed border?
Then consider the space you have available:
- Most herbaceous clematis grow to between 75cm and 1.5m tall, with a spread of less than 1m
- Climbing clematis range from very vigorous types, suited to covering a house wall or growing into a mature tree, to small and compact ones, suited to container-growing. The vast majority reach around 3m high
Most clematis grow best in a sunny or part-shaded position, but there are plants available to suit any aspect. Consider the conditions in your garden and choose a plant that will thrive there, whether that’s a shady wall or a particularly hot and sunny one.
If you want an evergreen clematis, bear in mind that these need a sunny, sheltered spot.
Clematis are grown for their flowers, so it makes sense to choose one that appeals to you most and works well with the rest of your garden:
- Do you want large, showy flowers, perhaps striped or double, or something more subtle and delicate?
- What colour would you prefer?
- Would you like scented flowers or decorative seedheads after flowering?
Consider if you would like your plant to flower at a particular time of year? Most herbaceous clematis flower during the summer, while climbing clematis are roughly divided into three groups:
- Winter and spring-flowering
- Early-summer-flowering (also known as twice-flowering as many produce a flush of flowers in late spring/early summer and another in late summer)
- Late summer and autumn-flowering
Some bloom over a long period, while others produce one big flush of flowers.
To help you decide
- Visit a garden known for its clematis display, like Sissinghurst, West Dean or RHS Garden Hyde Hall, or visit a local garden centre – seeing plants in flower allows you to compare colour, size and fragrance easily
- Visit a clematis specialist, either at an RHS flower show or at their nursery
- Visit a National Collection holder – in the UK there are collections of Clematis montana and C. viticella
- Get more information from the British Clematis Society or International Clematis Society
- Read the RHS Clematis alpina & C. macropetalum trials bulletin
Buying a clematis
Clematis are widely sold in garden centres and available mail order from many nurseries, including a number that specialise in these plants. Use our Find a Plant tool to find stockists.
Popular species and cultivars are often available year-round, while more unusual types may only be available at certain times of year. In garden centres, this is often just before flowering, when plants are in bud.
Clematis are usually sold as container-grown plants, with climbing types grown up a tripod of canes or small trellis for support.
Consider the following when choosing a plant:
- Well-developed plants with more than one stem growing from the base and growth that covers most of its support, will get going and flowering more quickly
- Roots should be developed enough to be visible through the holes in the base of the pot
- Avoid plants showing signs of stress, damage or disease
- Take care transporting your plant home, as clematis have quite fragile stems
When to plant
- The best time to plant clematis is in spring or early- to mid-autumn, as warm, moist soil at these times of year aids good root establishment
- If you buy a container-grown plant during the summer, plant it as soon as possible and water it regularly
- You can plant clematis at other times, but avoid planting in waterlogged or frozen soil and during periods of drought
Where to plant
Bear the following in mind when choosing a site for your plant:
- Most clematis will grow well in sun or partial shade, but flowering is normally disappointing in a very shady spot. Herbaceous types need a full sun position
- Some, including winter and spring-flowering evergreen types, need a sheltered spot as they are not as hardy
- Climbing clematis need their roots to be kept cool and moist, so plant the base of these clematis in light shade or provide shading with other plants or a dressing of pebbles
- Allow enough space for your plant to grow into – some clematis are vigorous climbers and will quickly become a nuisance in too small a space
- Consider how you will support your plant’s stems. Herbaceous clematis are best grown through plant supports or into nearby shrubs, while climbing types will need something to twine around, like trellis or mesh attached to a wall or fence
To allow your clematis to scramble over and properly cover its support, ensure mesh or trellis protrudes from the wall or fence by at least 2.5cm (1in). This is most easily done by attaching the mesh or trellis to 2.5cm (1in) deep battens at either end.
How to plant
Prepare your soil
Clematis are tolerant of a range of soil types, but grow best in deep, fertile, moist but well-drained soil. On heavy or sandy soils, dig-in some organic matter, like leaf mould or well-rotted manure, before planting to improve soil structure.
- Plant large-flowered hybrid cultivars (early and late-summer-flowering) with the top of the rootball 5-7.5cm (2-3in) below the soil surface. This encourages new shoots to grow from below ground level and also helps the plant recover if affected by clematis wilt
- Plant winter and spring-flowering clematis (including evergreens), late-summer and autumn-flowering species clematis and their cultivars, like Clematis viticella and C. tangutica, as well as herbaceous clematis, with the top of the rootball just below the soil surface
- If planting against a wall or fence, dig the planting hole so that the rootball will sit around 30-45cm (1ft-18in) from its base, and further out if there is guttering or an overhanging roof. Use a bamboo cane, if necessary, to help the plant reach its permanent support
Growing clematis into trees and shrubs
There are a few extra things to consider when planting a clematis to climb into a tree or large shrub:
- Plant the clematis on the windward side of the tree or shrub so that as it grows, and its stems extend, they are blown onto the trunk or into the branches, where they can obtain a hold
- Position the clematis at least 1.2m (4ft) away from the base of the tree or shrub to reduce competition for light, water and nutrients. This is particularly important if growing into a tree with a dense root system, like a beech or cherry, or into a conifer
- Use a bamboo cane or wires to help the clematis reach the trunk or branches, if necessary
- Avoid using clematis to cover dead trees or tree stumps as they can soon become hosts to diseases, particularly honey fungus
Growing clematis in containers
Smaller-growing clematis make attractive container plants, especially when trained up an obelisk or small trellis.
To grow clematis this way:
- Choose a pot at least 45cm (18in) deep and wide, and use a soil-based potting compost such as John Innes No. 2
- Remember clematis in containers still need their roots kept cool, so top-dress the pot with a layer of pebbles, plant low-growing plants like summer bedding in the same container, or position other planted containers on the sunward side
- Try not to position container-grown clematis right up against the base of a wall or fence, especially where there is guttering or an overhanging roof, as it can be very dry. Instead position around 30cm (1ft) away, or site in a more open spot
Clematis are thirsty plants, disliking soils that dry out during the growing season, when they can be prone to drought stress.
To keep your plant growing happily:
- Water newly-planted clematis regularly during periods of dry weather in the first few seasons after planting. Once established, plants shouldn’t need regular watering, unless growing on a very free-draining soil or during prolonged hot, dry spells
- As soil in containers dries out more quickly, container-grown clematis need particular attention. Water these most days between April and October, keeping an eye on moisture levels during dry spells at other times of the year, for as long as they stay in the pot
- Water thoroughly to soak the soil to around 30cm (1ft) deep, which for clematis in the ground, may require at least the equivalent of four watering cans per square metre
Clematis will grow and flower better given some regular, additional feeding:
- Feed those growing in the ground each year, in late winter or early spring. Apply a flower-encouraging potassium-rich fertiliser, like Vitax Q4 or rose fertiliser, around the base of the plant according to manufacturer’s instructions
- Mulch immediately afterwards with organic matter, like well-rotted manure, leaf mould or garden compost, to improve the soil and help conserve moisture
- Feed container-grown clematis monthly during the spring and summer using a general-purpose liquid fertiliser
It can seem unnecessary to tie-in climbing clematis, as they naturally twine very readily using their leaf petioles (stalks). However encouraging this process, and guiding stems so they spread out evenly over their support, improves flowering and helps prevent a tangled mass of foliage.
It may be necessary to tie stems in place with twine until they have secured themselves. Do this carefully, as clematis stems are fragile, using loose figure-of-eight knots (where the twine passes between the stem and support). Ideally don’t use plastic twist-ties, as these can cut into and damage stems.
Herbaceous clematis are non-climbing and many have sprawling, floppy stems. If growing these with plant supports, as opposed to letting them scramble through a nearby shrub, then these too will need tying-in.
RHS Guide to training climbers
RHS Guide to staking perennials
Clematis in containers have a restricted root run and so need more regular care than those growing in the ground to stay happy and healthy. This includes top-dressing pots each spring, removing the top 5cm (2in) of old compost and replacing with a fresh layer. Our guide on container maintenance below gives more information.
Regular pruning encourages strong, healthy growth, improves flowering and keeps clematis plants in check. Left unpruned, these climbers tend to form a mass of tangled stems with bare bases and flowers well above eye level, so although it can be a time-consuming task, it is well worth the effort.
Pruning newly-planted clematis
To encourage bushy plants with multiple stems, it’s a good idea to give all newly-planted climbing clematis an initial prune:
- Cut back all stems to 15-30cm (6in-1ft) from ground level, cutting just above a bud
- Prune autumn-planted clematis in the February or March after planting, and spring-planted clematis immediately after planting
- Once new growth appears, pinch out young, developing shoots to a lower bud to promote further branching
Pruning established clematis
Clematis have a reputation for being difficult to prune, but they aren’t as long as you know when your plant flowers, as the three clematis pruning groups are based on flowering time:
- Pruning group one – Clematis that flower in winter and spring on shoots produced the previous summer
- Pruning group two – Large-flowered cultivars that flower in early summer (May and June), including those referred to as twice-flowering. These produce flowers on short shoots from last year’s growth, with a later flush on new growth
- Pruning group three – Climbing clematis that flower from mid-summer (late June onwards) on new, current season growth, and herbaceous types
If you are unsure of which group your clematis falls into, observe the flowering time and follow this simple guide:
- Flowering before early summer (June): do not prune
- Flowering from late June onwards: prune in late winter (February)
Renovating overgrown clematis
Many clematis will tolerate hard pruning, to near ground level, if they have become overgrown or top-heavy. See the individual pruning groups above for more advice on the suitability of different clematis to renovation, as well as information on when and how to hard prune.
There are a few methods you can use to create new plants from your favourite clematis:
Clematis from cuttings
This is the most popular method of propagating clematis and allows you to create many identical copies of named cultivars.
Take double leaf-bud cuttings, which are similar in technique to semi-ripe cuttings, from healthy, non-flowering shoots between spring and late summer. Given warm, humid conditions, cuttings usually root within 6-8 weeks and will be ready for potting-up individually the following spring. Expect flowering within two years.
Serpentine layering, carried out between late winter and spring, is an easy method of propagating a small number of clematis plants and involves looping stems in and out of the soil to encourage the buried sections to root. It is particularly suited to those like Clematis montana and C. viticella, that naturally produce long, flexible stems.
It takes one to two years for buried stem sections to produce a good root system of their own. After this period, sever stems from the parent plant and pot-up or plant out, for flowers the following season.
Clematis from seed
Species clematis (i.e. not hybrids or named cultivars) can also be propagated from seed. Although a slower process than making new plants from cuttings or layering, it can be quite exciting, as seedlings will look at least slightly different from their parents and could have new or unusual flowers.
- Ideally sow clematis seed fresh in the autumn, into pots of a gritty seed compost, and cover with a fine layer of compost and grit
- Keep pots in a cold frame or unheated greenhouse over winter – this provides the period of chilling needed for good germination
- Seedlings should germinate in spring. Prick out when large enough to handle and pot-up individually, firstly into 9cm (3½in) pots and then into 15cm (6in) or 2 litre pots when well-rooted
- Grow on until well-established, providing support for climbing stems, before planting out
- Plants may take over three years to flower
Please be aware that some clematis are protected by Plant Breeder’s Rights, and you are not allowed to propagate them for sale.
Clematis can suffer from a range of pests, diseases and disorders that can affect vigour and flowering display.
Some of the most common problems include:
- Pest damage by aphids, capsid bugs, earwigs, slugs and snails. Container-grown plants may also suffer damage by vine weevil larvae
- Pruned stems failing to reshoot and oozing a slimy substance as a result of clematis slime flux
- Clematis green petal, where green flowers are produced early in the season
In many cases it is unsuitable growing conditions that are to blame. Water-stressed plants are more prone to powdery mildew for example, while the blooms of some early-summer-flowering cultivars can fade prematurely in too bright a spot.
The fungal disease clematis wilt causes wilting and blackening of the stems of large-flowered (early or late-summer-flowering) hybrid cultivars. Where wilting is seen on other types of clematis, the cause is more likely to be environmental problems, like drought stress as a result of growing in poor, shallow soil. Slug damage can also produce similar symptoms, where stems are partly eaten in the search for new foliage, collapsing as a result.
If you are not sure what is wrong with your clematis, then this guide is a good place to start:
Or, of you are a member of the RHS, you can use our online gardening advice service, via MyRHS.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.