How to Prune Your Clematis
April 24, 2011

When it comes to Clematis we get more questions about this than anything else. Confused and worried gardeners call us wanting to know how to prune their plants as though they would die without this surgery. The confusion is understandable as many books on Clematis and their pruning are written by English gardeners. Our climate isn't like England's.

Clematis vines growing in the wild aren't pruned (perhaps occasionally munched on) and still thrive, so don't worry if you didn't get around to pruning your plants. Unpruned vines may not look as nice or bloom as profusely but they won't die. The problem lies in the so called "pruning groups" you reaf about in the books.

Unlike England, we have a pruning phenomenon called winter. Our winters vary: some years are mild others bitterly cold. Some winters start early while others are late. These winter variations have an impact on how your plant performs.

Another problem is that we forget what we've planted or we inherit plants from previous gardeners. Fortunately these problems can be overcome. Much as I disregard gardening "rules", the following are the result of 25 years of experience with these wonderful plants PLUS the invaluable advice we've received from our customers.

Dugald Cameron

President & resident clematis nut

1) We prune to encourage more flowers. The biggest mistake is when neat gardeners feel they must "tidy up" in the fall by pruning their vines. Well, unless the plant is threatening the safety of people or property I'd leave it alone until the spring. It is far better to wait until spring to see what winter has killed and tidy up then.

2) If your plant blooms very early and has flowers (such as JOE ZARY on the left), then it is likely to be one of the Atragene group, like C.alpina, C.macropetala or C.koreana. These bloom on the previous seasons growth and are among the hardiest of clematis. They don't need much pruning other than to control their predigious size. As a rule they bloom towards the top.

3) If your plant blooms in the spring with great big flowers then it is likely to be from the C.patens or C.jackmanii groups. Those in this group are among the most common because they are in flower at garden centres in May when gardeners make their lemming like migration to buy whatever is in bloom and have it planted by May 24. These too bloom on the previous seasons vines but can also bloom again later in the season on current growth. A classic example would be C. GUERNSEY CREAM on the left. These also vary a great deal in mature height with newer varieties being shorter. I suggest you prune back to the second or third pair of buds above the ground if they've had a hard winter with substantial dieback. If the winter has been kind you can either do a light prune at the tips or cut back to the second or third buds AFTER it has flowered in the spring to encourage new growth and a better second flowering in late summer.

4) If your plant has loads of small flowers in early to midsummer OR doesn't climb, then it is likely to be from the C.texensis, C.viticella or its related C.diversifolia groups. These are undeservedly less common because of their later flowering and reputation for smaller flowers. They more than make up for it in sheer abundance and extended bloom period. If the winter is mild and you've got a C.texensis or C.viticella they'll just grow bigger still and will flower well if left unpruned. But you can also prune these back to the second pair of buds to reduce their size OR prune them right back to the ground if, like me you have a lot of plants in a limited space. C.diversifolia is best pruned to the ground. This tolerance of hard pruning makes these clematis groups ideal companions for shrubs and roses. It's way easier (and less painful) to prune a climbing rose/clematis combination if you can deal with the clematis first.

5) If your plant blooms most of the summer or in late summer, has white or yellow flowers and is fragrant then it is likely from C.mandschurica, C.vitalba, C.orientalis groups or is C.terniflora (sweet autumn clematis). With the exception of C.mandschurica these are big plants, hardy plants that bloom on new growth from the previous season's vines. You prune these to control their size.

6) The last and perhaps most important rules are to buy good, well grown (avoid bare root which lack "feeder roots") correctly labelled plants. There are two planting techniques: the right way with a 60 x 60cm wide and deep hole filled with compost and manure and setting the plant a little deeper than in its pot. The wrong way is called the "coffee can" approach. Thia is when a coffee can sized hole is chisseled out of poor soil and the plant is plunked in. This is a bad idea. Remember to feed your plants. Clematis are like roses and benefit from a frequent top dressing of well rotted manure and/or compost.

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