Clematis is a perennial climber that comes through the winter in open ground and flowers somewhere between May and October depending on the variety. Two things decide whether the plant covers the trellis with flowers or stands half bare: which pruning group it belongs to and how deep it was planted. Both can be got right from the start, and both can be corrected on a plant you already have.
Pruning groups 1, 2 and 3
The pruning group is usually printed on the label, but the label is sometimes missing in the shops. The group tells you where the flower buds sit, and that decides when you are allowed to cut. Cut a group 1 clematis down in March and you remove the whole of this year's flowering, because the buds are sitting on last year's wood. Leave a group 3 plant unpruned and it goes bare for the lowest couple of metres and flowers only at the top. Same genus, three different jobs.
| Group | Examples | Flowering | Buds sit on | What you do and when |
|---|---|---|---|---|
| 1 | Alpine clematis (Clematis alpina) with varieties such as 'Pamela Jackman' and 'Willy', Clematis macropetala and other Atragene clematis, plus mountain clematis (Clematis montana) | May to early June, one flush | Last year's wood | Do not prune at all in a normal year. Take out dead shoots and thin after flowering in June or July. If the plant has gone twiggy you can renovate it down to 50-100 cm, at most every third year. |
| 2 | Early large-flowered varieties such as 'Nelly Moser', 'The President', 'Doctor Ruppel', 'Multi Blue' and 'Piilu' | May to June, often a second flush in August and September | Both last year's wood and this year's shoots | Light pruning in February or March. Follow each shoot from the top downwards to the first pair of live green buds, cut just above them and discard the dry piece. Deadhead after the first flush. |
| 3 | Late large-flowered such as 'Jackmanii' and 'Hagley Hybrid', Viticella clematis such as 'Étoile Violette', golden clematis (Clematis tangutica) | July to October | This year's shoots only | Cut hard every year in February or March, down to the lowest pair of buds, roughly 20-30 cm above the ground. The whole plant is rebuilt each season. |
How to tell which group you have when the label is gone
The label often disappears in the first season. The flowering gives the group away:
Flowers before the end of June and then no more: group 1.
Large flowers in May or June, and again in August or September: group 2.
Sets buds only in July or later: group 3.
If you are unsure between 2 and 3, treat the plant as group 2 the first year and note when it flowers. Too light a cut on a group 3 plant only makes it taller and later. Too hard a cut on a group 2 plant costs you the whole early summer flush.
Plant 5 to 10 cm deeper than the pot stood
Clematis goes in deeper than almost anything else in the border, and that is deliberate. Large-flowered varieties and Viticella clematis are planted with the top of the root ball 5 to 10 cm below the soil surface. The species in group 1 go in with the root ball just below the surface.
The reason is that two or three leaf nodes then end up under the soil, and every node holds dormant buds. If the whole above-ground part dies from clematis wilt, the plant can send up new shoots from those buds down in the soil. A plant set level with the surface has nothing to shoot from. Deep planting is an insurance, not a growing trick.
Set the plant a good distance out from the house wall, clear of the drip line from the roof, and lean the root ball in towards the support. Then cut the newly planted clematis back to about 20 cm. It feels harsh, but it forces several shoots from the base instead of a single one that goes bare at the bottom.
Cool feet and a sunny top
The old rule holds. The shoots want sun or partial shade, while the root zone is kept cool and moist. Lay a flat stone over the soil at the foot of the plant, or plant low perennials on the sunny side so they shade the ground without growing into the root ball. Atragene clematis and Viticella clematis cope with a north-facing spot as well, while the large-flowered varieties want at least a few hours of sun to set buds.
A support the leaf stalks can grip
Clematis climbs with its leaf stalks. The stalk winds a couple of turns around whatever happens to be nearest and holds the shoot in place. That puts one demand on the support: it has to be thin enough to wind around. A smooth post, a wide board or a rendered wall gives the leaf stalk nothing to take hold of, and the plant slides down as soon as it gets heavy with flowers.
Netting with a mesh of a few centimetres, a trellis with thin battens, tensioned wires or an existing shrub all work. If the trellis sits on a wall it should stand at least 2.5 cm clear of it so the shoots can get round the batten. Compare with ivy, which fastens with aerial roots and manages a smooth facade, and with honeysuckle, which twines with the whole shoot and manages thicker posts.
In the first season the clematis puts its strength into roots and rarely covers more than a third of the netting. If you want greenery on the support the same summer, sow an annual climber alongside, for example cup and saucer vine or sweet pea. The sowing is described in the guide to growing cup and saucer vine.
Soil, watering and feeding
Soil: deep, rich in humus and moisture retentive but well drained. On poor soil, mix in compost or well rotted manure. A layer of gravel on top improves drainage closest to the stem.
Watering: clematis is thirsty and does not tolerate dried out soil during the growing season. Keep the soil moist for the first two years and water in dry spells in years three and four as well. In a pot it needs water almost every day between April and October.
Feeding: give no fertiliser in the planting year. In rich garden soil, compost in spring is enough after that. In a pot, give a balanced liquid feed through spring and summer.
Weeds: keep the root zone clear for the first three years. The roots compete poorly while the plant establishes.
Clematis wilt and what you do about it
Clematis wilt is caused by the fungus Calophoma clematidina, formerly called Phoma clematidina. It starts with dark spots on the leaves. Then a whole shoot collapses within a day or two even though the soil is moist, and if you split the shoot lengthwise you can see black discoloured wood.
It is the large-flowered hybrids that are hit, among them 'Nelly Moser', 'Jackmanii' and 'Marie Boisselot'. The small-flowered species go largely free: alpine clematis, mountain clematis and golden clematis. Viticella clematis counts as tolerant rather than completely spared.
Cut away everything that has wilted down to healthy wood with no black discolouration. If the cut surface is dark, go further down.
Bin or burn the material. Do not put it in the compost, or you spread the fungus back into the border.
Clean the secateurs between cuts and before the next plant.
Wait for new shoots. A deeply planted clematis often sends up new shoots from the nodes below the soil surface, within a few weeks or by the following spring. Do not dig the plant up before you have given it a full season.
There is no product to treat it with. If you want to avoid the problem altogether, choose Viticella clematis or alpine clematis instead of a large-flowered hybrid. Here the choice of variety is the whole of the plant protection.
Four mistakes that cost you the flowering
Spring tidying without checking the group: a general cut back in March wipes out the flowering in group 1 and halves it in group 2.
Planted too shallow: a root ball level with the soil surface leaves the plant without a reserve if the top dies.
Too thick a support: a support the leaf stalk cannot reach around leaves the shoots on the ground.
Impatience in year one: a newly planted clematis is building roots. Expect sparse flowering in year one and full flowering from year three.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-09-01