Pruning worries gardeners more than any other clematis job, yet it rests on one question: when does your plant flower, and on what wood? Answer that and the three pruning groups fall into place.
Why clematis are split into groups
Some clematis flower on stems that grew the previous year; others flower on shoots made in the current season. Cut the first kind hard in winter and you remove this year's buds. Leave the second kind unpruned and it flowers ever higher above a bare tangle of old stems.
The British Clematis Society sums it up: if it flowers before June, don't prune it in winter. The RHS gives the same advice when you don't know the group, adding that plants flowering from late June onwards can be pruned in February.
The three pruning groups at a glance
| Group 1 | Group 2 | Group 3 | |
|---|---|---|---|
| Flowers on | Last year's growth | Short shoots on old stems | This year's growth |
| Typical plants | Montana, alpina, armandii | Early large-flowered hybrids | Viticellas, late hybrids |
| Routine pruning | Little or none | Light trim | Hard cut |
| Cut back to | Tidy after flowering | First pair of strong buds | Lowest buds, 15–30cm up |
Flowering and pruning calendar
Group 1: early flowerers
Group 1 covers the early flowerers: C. alpina, C. macropetala, C. montana, the evergreen C. armandii and C. cirrhosa, and the New Zealand hybrids.
What to do
Removing faded flowers and a light tidy are usually enough. If a plant outgrows its space, prune straight after flowering, once frost risk has passed, so it has the season to make next year's flowering wood. On winter-flowering types such as C. cirrhosa, leave the new green stems alone: they carry the flowers.
To renovate a neglected plant, the RHS suggests cutting stems to about 15cm from the base after flowering, but not again within three years. A big montana can take a while to recover, so renovate only when you must.
Group 2: early large-flowered hybrids
These hybrids open their biggest flush from late May to June on short shoots from last year's stems, often with a smaller second flush in late summer. RHS examples include 'Nelly Moser', 'Bees' Jubilee', 'Doctor Ruppel', 'Marie Boisselot', 'The President' and 'Snow Queen'.
The late-winter tidy
Group 2: the late-winter tidy
- Pick the momentWork in February or early March.
- Clear outRemove dead, weak and broken stems first.
- Work down each stemStart at the top of each remaining stem and look for buds.
- Cut above strong budsCut just above the first pair of plump, healthy buds. Going lower removes the wood that carries the early flowers.
- After the first flushCut some stems back to a large bud or strong side shoot just below the spent blooms.
After the first flush
If the plant has become top-heavy, the RHS suggests reducing it gradually over two or three seasons by pruning harder after the first flush. Alternatively, every three or four years, cut the whole plant to 30–90cm in late winter and accept a single, later flush.
Group 3: late-summer flowerers
Group 3 clematis flower from late June on stems made that year. They include viticellas such as 'Étoile Violette' and 'Polish Spirit', 'Princess Diana', 'Ernest Markham', 'Ville de Lyon' and the non-clinging 'Alionushka'. Their simple pruning makes them the usual choice for growing through roses.
How hard to cut
These are the easiest clematis to prune: every stem goes back to the lowest pair of healthy buds, removing everything above. Don't rush in a cold spring, as very early hard pruning can expose tender new shoots to frost.
The exception: seedhead clematis
Small-flowered types grown partly for their seedheads, such as C. tangutica and 'Bill MacKenzie', can instead be thinned and trimmed back to a framework, so you keep the silky seedheads into autumn.
The in-between plants
Some popular summer clematis fit either group 2 or group 3: the RHS names 'Comtesse de Bouchaud', 'Gipsy Queen', 'Hagley Hybrid', 'Jackmanii', 'Perle d'Azur', 'Rouge Cardinal' and 'Star of India'. Keep a framework on some stems and cut others hard to the base, which staggers flowering and lengthens the season.
Pruning a newly planted clematis
Young plants benefit from a hard cut that encourages several stems from the base. For groups 2 and 3, unless the plant already has three or four healthy stems, the RHS advises cutting it back in the first spring to a strong pair of buds about 30cm from the soil. Our guide to planting a clematis covers this step.
If you have lost the label
Watch the plant for a season and note when it flowers, how big the flowers are and whether they appear on old or new stems. Then use the quick check below.
Following RHS and British Clematis Society advice: flowering before June on the previous year's growth means group 1 (no routine pruning, trim straight after flowering if needed); large flowers in late May to June on short shoots from last year's stems, often repeating in late summer, means group 2 (light trim to the first strong buds in February or early March, and again after the first flush); flowering from late June on the current year's growth means group 3 (cut hard to the lowest healthy buds, 15–30cm up, in February or March) – a rule of thumb, since some cultivars such as 'Jackmanii' or 'Perle d'Azur' can be treated as group 2 or 3. — Sources : Clematis: pruning (RHS)
A wrong guess is rarely fatal: at worst you lose a season's flowers. If a clematis refuses to bloom despite correct pruning, check its site and its feeding and watering before blaming the secateurs.
Tools and technique
Use clean, sharp secateurs and cut just above a pair of buds. Untangle carefully: stems are brittle, and one that looks dead at the top is often alive lower down. Tie in new growth with soft twine in loose figure-of-eight loops.
If it flowers before June, leave it alone in winter (group 1); give early large-flowered hybrids a light trim to the first strong buds in February (group 2); cut late-summer flowerers hard to the lowest pair of buds, 15–30cm up, in February or March (group 3).
Sources
- Clematis: pruning (RHS) — Overview of the three groups, renovation of group 1 and the rule for unknown varieties.
- Clematis pruning: group three (RHS) — Hard pruning to 15–30cm, first-spring pruning of new plants and lists of group 3 and group 2/3 cultivars.
- Clematis pruning: group two (RHS) — Light late-winter pruning, post-flowering cuts and renovation of overgrown large-flowered hybrids.
- Pruning (British Clematis Society) — The 'flowers before June, don't prune' rule, winter-flowering types and pinching out group 3 shoots.