Documents: Garden Design:

Pruning Clematis
by Des Kennedy
by Des Kennedy

Des Kennedy is a celebrated public speaker, having performed at numerous conferences, schools, festivals, botanical gardens, art galleries, garden shows and wilderness gatherings in Canada and the U.S. His humour, irreverence and passion for gardening and the natural world have made him a 'must see' speaker in demand across the country.

February 27, 2005

Late february is the recommended time for pruning some types of clematis, but few assignments more befuddle certain gardeners than knowing how and when to prune these vines.

Hundreds of varieties and species are in the marketplace, virtually all of them exquisite in bloom. But when it comes to pruning, not all clematis are created equal. Except at planting time, that is, when all of them should be cut back hard to the lowest pair of strong buds in order to encourage multiple stems.

Thereafter things become cloudier and rather like the mystery of the Blessed Trinity which the good nuns would try explain to us adolescent Catholics in catechism class. Clematis, too, are three in one, requiring three distinct pruning regimes, each based on the age of wood upon which flowers are borne.

The vines we’re out pruning just now are those that will only bear flowers on new growth developed during the coming growing season. They’ll spend the spring and early summer growing, some of them exuberantly, then flower in summer and late fall.

One of my favourites in this class is ‘Huldine’ which bears hundreds of pearly-white, translucent blooms suffused with mauve. At our place it begins flowering in late August, sometimes carrying on into October. We train it up over the rose arbor so that its long trailing stems form a cascade of bloom. Then all winter it hangs there, dead brownish leaves and a rather derelict look.

I’ve just now cut it back and, as with all these late-flowering types, one cuts to ground level, just above the lowest pair of strong buds on each stem.

Left unpruned, the vine would produce new growth from where it left off last year, with far fewer flowers and an awful tangle of scraggly growth near the base. The only case in which you don’t radically cut back these vigorous late-blooming varieties is when one’s been encouraged to run up into a tree, in which case it’s left to its own devices.

Other popular varieties and species that get the same late February pruning include ‘Etoile Violette’ with its multitudes of deep violet flowers, splendidly red ‘Ernest Markham,’ and velvety-purple ‘Lady Betty Balfour.’ As well the texensis types, including rosy-pink ‘Duchess of Albany,’ and pinkish-white ‘Duchess of York.’ And probably the most familiar group of all, the many consistently reliable Jackmanii varieties.

We’ve got a baker’s dozen of these at our place, and by the time I’ve gotten through late winter pruning, there’s an enormous ball of woody threads, like a cartoon character’s outlandish string collection. I find the best way of dealing with the prunings is to push them through the shredder, then into the compost heap.

The vines we musn’t touch this time of year are those that will bloom between April and June. Their flowers develop on short shoots growing from stems produced last summer. Pruning out the stems now would simply eliminate the plant’s opportunity to flower.

Included here are the vigorous and spectacularly blooming montanas as well as the smaller alpina and macropetala varieties. Mature plants are pruned, when necessary, imediately after the flowers have faded, by cutting away the flowered wood to within a dozen or so centimetres of the main stems. This stimulates new growth that will bear next spring’s flowers.

The exception here is when older plants need radical rejuvenation; this too is done late winter/early spring by cutting the old stems back to about a metre high, thereby sacrificing the spring bloom for a year or two until the vine has regrown.

The third wing of the clematis trilogy are in a sense the most challenging because they flower twice each year, on different aged wood; but in another sense they’re the least demanding because they seldom require much pruning at all.

These are the hybrids that produce large flowers between May and July on last year’s wood, then put out new shoots that bear flowers later in the season. Perhaps the most popular of them is ‘Nelly Moser,’ whose large flowers have pale mauve-pink sepals with a carmine stripe down the centre.

When we planted this specimen, we were following some expert’s suggestion that clematis do well entwined with climbing roses, so poor Nelly got plunked at the base of a rampant ‘New Dawn’ rose. Her slender arms twine through the rose alright -- though suggestive of a skinny fashion model clinging to a brawny hunk -- and make a complete nuisance of themselves at rose pruning time. But we’ve come to view her saucer-sized flowers as perhaps a bit overdone, so we’re happy to have them tucked in amongst the rose foliage.

The most these early bloomers need is an occasional thinning out of entangled stems, done after the spring flowers have faded; otherwise they’re best left well alone.

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