by Dr John Howells

First published in Garden News, Jan. 13th 1997

The key to knowing clematis is to think of them in 12 groups. The key to knowing their pruning is to divide them into three classes. These are: those needing no pruning; those needing light pruning; those needing hard pruning - to the ground
A good rule to remember is that the earlier the clematis flowers the less pruning it needs; the later it flowers the more pruning it needs.

The 'No-pruning' Class
Five groups of clematis, all flowering before June, need no pruning. The first group is the Evergreen Group containing clematis such as Clematis cirrhosa and Clematis armandii, flowering before April. The second group is the single belled Alpina Group with such as C. alpina 'Frances Rivis' flowering March time. The third group is the double belled Macropetala Group with, for example, C. macropetala 'Markhamii' flowering with or soon after the Alpinas. The fourth group is the lovely rockery clematis such as 'Cartmanii Joe', flowering late April. The last group is the giant Montana Group containing such as C. montana 'Mayleen' flowering from May onwards.

All these will usually flower for years without pruning. Rarely will pruning be necessary except under two conditions. Firstly, if the plant has overgrown the area you gave it. In this event prune after flowering, so that you lose no colour. Prune back below the area you gave it and by the end of the season it will have filled the allotted area. Secondly, if the plant is becoming weak in its growth it may need the 'tonic' of hard pruning. The 'tonic' may kill your plant. So hedge your bets, pruning half the first year and prune the rest the following year. At the same time as you prune check that the plant is receiving enough water and give it a good fertilising.

The 'Light' Pruning Group
Only one Group is in this class. This is the Early Large Flowering Group which contains the 'show stoppers' such as 'Nelly Moser', 'Lasurstern', 'Mrs Cholmondeley', 'Dr Ruppel', and 'H.F. Young'. They flower from May onwards. The clematis in this Group are given to stem rot (clematis wilt).

After the plant has recovered from winter, when showing green growth but not in flower, cut out any dead material. This is in February-March time. Then starting at the top of each stem follow with your eye down the stem until you come to two strong growing buds. Cut above the buds. Do this on all the stems.

Here is an extra tip for strengthening your plant. The number of flowers you get next year will depend on the new growth your plant makes this year. So to encourage it to make new growth cut all the stems back to half way after the plant has flowered. It will reward you with a big display next year - and maybe even this autumn.

The 'Hard Pruning' Class
Six clematis groups are in this class. They all flower after June. Firstly there is the Late Large Flowered Group containing plants such as 'Jackmanii', 'Comtesse de Bouchaud', 'Victoria', 'Hagley Hybrid', 'Gipsy Queen', etc. The second group is the trouble-free Viticella Group containing such plants as 'Madame Julia Correvon', 'Ville de Lyon', 'Etoile Violette', 'Abundance', 'Kermesina', etc. The third group, the Herbaceous Group, contains all the integrifolias and heraclefolias. The fourth group, the Texensis Group, contains tulip like flowers such as 'Princess Diana', 'Gravetye Beauty', 'Sir Trevor Lawrence. The fifth group is the Orientalis Group with its yellow flowers such as 'Bill MacKenzie', the tanguticas, serratifolia, rehderiana. The sixth group are the Late Mixed Group containing plants such as C. flammula, C. vitalba, C. terniflora and C. fargesi..

This used to be a troublesome group to prune. We have now simplified it. So very simple. You just cut all stems at ground level. We were very slow to appreciate this was the way to do it. Indeed the plants told us because left to themselves they withered each year to the ground.

When do you cut to the ground? In February-March time. Gently scratch the ground and you will find the new shoots just waiting to spring up. There is no virtue in pruning too early as you do not want to subject these tender new shoots to hard late frosts. Also they are all strong growing plants making a lot of quick growth and, of course, they won't be flowering until late in the season.

There is one modification you may care to use. Many plants in this class are climbing up shrubs. The clematis can be unsightly with their black leaves. So in the autumn prune to 1m (3ft), bring the stems together with a tie and now you can tuck them away out of sight. The stems will still give some protection to the crown of your plant. Complete the pruning in late winter.

Yet another modification can be useful if your plant has a long way to climb. Instead of pruning to the ground, prune 1m (3ft) from the ground every year. The plant will develop strongly woody stems in its bottom 1m (3ft). You have now given the plant a lift to help it on its long way upwards. It's cleverly done on the tall pergola in the Rose Society's Garden of the Rose at St Albans.

New Plantings
When you bring your recently bought clematis back home in its pot, you will naturally be looking forward to seeing it in bloom. If you can't resist let it bloom. But immediately thereafter or preferably as soon as you put it into the ground, cut all stems down to the first node above the ground. Two things may happen to the benefit of the plant. Firstly, one or more extra shoots may appear from the ground, making it a far stronger plant. Secondly, from the node two side shoots will appear. Let each new shoot grow a foot or so and then pinch each shoot above a node. (See Figure 3). Keep doing this and you will have a strong nicely structured plant.

Some readers will be saying - "with the best will in the world I just don't have the time to prune my clematis". Don't worry. With all the groups I mentioned you will still get a good display with no pruning. But after four or five years of no pruning you may have a much-tangled plant. Cut below the tangle and off you go for some more years.

Reproduced by kind permission of Garden News.

Site created and maintained by Studio 46