Clematis Classics

Credit: John Glover

The genus Clematis comprises some 200 species ranging in origin from all over the globe, and encompasses sprawling climbers, evergreens and even woody-based perennials. Mention the word “clematis” to any bunch of gardeners and eyes begin to light up, followed by personal stories about favourite cultivars or species, both current and from gardens past. Common names for this group of plants, which hails from the buttercup family Ranunculaceae, also conjure up comforting associations – traveler’s joy, old man’s beard and virgin’s bower are but a few of the time-honoured names by which this beloved plant is known.

Although clematis can inspire much affection, novice gardeners are sometimes put off growing these plants when they read up on the various groups and different pruning methods. Don’t be discouraged, however, as there are so many clematis to choose from out of hundreds of species and countless named cultivars.

Some definitely require a soil that is a little on the alkaline side. The one general requirement of clematis is that they like their roots to be cool and shaded. In nature their roots are either sheltered behind rock outcroppings, or in the shade of other shrubs, and both of these conditions are easy to duplicate in a home garden.

Let me share some of my favourite clematis with you. On the coast, one of the most pleasing and earliest species to bloom is Clematis cirrhosa, a somewhat tender evergreen climber, which comes to us from southern Europe. In the early days this one was mistakenly known as Clematis balearica. There is one fragrant form, C. cirrhosa var. balearica, native only to the Balearic Islands just off the Mediterranean coast of Spain.

The tiny evergreen leaves of C. cirrhosa are dark green, deeply trilobed with bronze/green undersides, and measure about five centimetres in length. The flowers, which appear late winter to early spring (February/March, or sometimes earlier in very mild winters), are open bell-shaped, drooping with four six-centimetre-long tepals that are cream coloured with tiny reddish dots on the inside. Sometimes the flowers are borne singly, while others come in clusters of three or more.

Because of its tenderness (zones 7 to 9) and early flowering, C. cirrhosa needs to be grown in the lee of outflow winds, near an entryway or somewhere it can be seen from the house. At the UBC Botanical Garden we have one trained around a south-facing doorway, while the other climbs up through the branches of winter-flowering Garrya elliptica (silk-tassel bush). The combination of the two in late winter is a joy to behold. As far as cultural conditions go, both benefited from some well-rotted compost added to their planting holes. But now, with no further special attention, our C. cirrhosa thrives in our naturally acidic west coast soil. In fact, the one around the doorway is on the edge of a gravel path with its roots shaded by a tree on the opposite side of the path.

Another early bloomer that may be enjoyed over a wider growing area of our province is Clematis macropetala, which originates from Siberia, Mongolia and China, making it hardy in zones 5 to 9. A deciduous climber whose fresh green foliage and flowers appear early in spring, this one blooms on the previous season’s wood. The 10-centimetre open bell-shaped flowers are blue to violet-blue and appear to be double in that they have four long sepals with shorter petaloid stamens within, giving them a fuller, attractive mop-like effect. Again, this particular plant does not seem too concerned with its soil conditions. One of our best specimens is planted up on the edge of a southwest-facing, thick two-metre retaining wall that provides shade for the roots. Here, its branches tumble over the wall’s edge, and in spring the full bright-blue flowers look down as one passes by.

In a Victoria garden, I have seen C. macropetala climbing up through the branches of a purple-leaved plum (Prunus cerasifera ‘Nigra’). The combination of the blue flowers with the fresh plum colour of the foliage is quite stunning.

There are so many other clematis to choose from, but I can’t leave out Clematis montana, another early-flowering deciduous vigorous climber that comes to us from the Himalayas (hardy in zones 6 to 9). At UBC we have them climbing high into red cedars and grand firs, where they can reach a height of 30 metres. They are a sight when their full bloom tumbles down like waterfalls of blossom against a backdrop of evergreen branches in late May or early June.

The original C. montana has solitary white flowers five centimetres across with creamy-white anthers in the centres. There are, of course, gorgeous pink forms, C. montana ‘Pink Perfection’ being one to look for as it produces fragrant blossoms. Years ago, when I lived in a townhouse, I had this one trained around a sliding patio door so that the scent could drift in whenever the door was ajar. The downside was that the plant was so vigorous that almost twice a month throughout the summer I had to prune its shoots out from growing up, through and underneath the roof shingles.

My late friend Barbara Durrant grew C. montana var. rubens up through the branches of a shrubby dogwood so that all the blooms could be enjoyed at eye level in late spring and early summer.

Having mentioned that C. montana will grow happily up through established evergreens, I should explain that when planting, you should dig a decent-sized hole (45 centimetres deep and a metre across) at least one to two metres from the base of the tree. Work in plenty of compost and plant the clematis. As the clematis gets established, use a long cane to support it and lead it to the tree in which you want it to climb. That has been the key to the success of ours in the Asian garden at UBC. And it seems they prefer the acidic soil of the conifer forest, too.

So far, all the clematis I have mentioned do not require pruning, but we should now talk about one that does. I know clematis growers will throw up their hands in horror when I say that out of all the gorgeous garden hybrids out there, I still love Clematis ‘Jackmanii.’ It, of course, has been around for years; my grandmother had one covering a metal-hooped archway that led down her garden path.

It is late and large flowering with velvety, dark-purple, abundantly produced blooms covering the plant from top to bottom. They measure eight to 10 centimetres across and look magical against dark-pink climbing roses and tall spikes of blue delphiniums. You get the picture. There is also a more difficult to find white-flowered form of this plant, C. ‘Jackmanii Alba,’ which is stunning with single to semi-double white flowers tinged with blue.

The amazing fact about this plant is its hardiness. I have seen it blooming profusely on the south-facing wall of a home in Saskatoon, which makes it hardy in zones 4 to 9. All of our friends up north can enjoy this one, too. The reason for its success is that it can be frozen back to its base each season, allowing for good strong growth from the base every spring. On the coast and in other milder areas of the province it should be cut back to within an inch of its life in February.

Here’s a tip from my friend Jo Bridge. Because C. ‘Jackmanii’ and other hybrids like a slightly alkaline soil, she has found that incorporating small pieces of broken patio concrete into the soil around them works like a charm. As the concrete breaks down, it releases small amounts of lime into the soil, making the clematis very happy.

One more species I must mention is a shrubby herbaceous clematis from central Europe that is extremely hardy and enjoys a slightly alkaline soil. Clematis integrifolia (zones 3 to 7) reaches a height and width of about 60 centimetres. It doesn’t climb, but forms a nice clump with a somewhat woody base. The foliage is lance-shaped to elliptical and the solitary but readily produced mid-blue bell-shaped flowers (five centimetres in length) have slightly twisted sepals and lovely cream anthers. These blooms are followed by silvery seedheads. This makes a pleasant plant for a mixed perennial border, yet it isn’t widely grown.

There are so many wonderful clematis to choose from. Here are a few more favourites.

Clematis ‘Dr. Ruppel’ (zones 4 to 9) is a magnificent early bloomer with pink flowers 10 to 15 centimetres across. Each deep rose-pink sepal has a darker stripe down the middle, making this a real showstopper.

Clematis ‘Barbara Dibley’ (zones 4 to 9) blooms with petunia-red flowers late spring/early summer on old growth. At UBC we have one climbing on a chain-link fence near the entrance, and people make a track through the flowerbed each year to get a closer look at its beautiful blooms.

More of a collector’s plant and suitable only for coastal gardens, Clematis ‘Early Sensation’ (zones 7 to 9) forms an evergreen shrub up to two metres in height covered in creamy-white flowers with green centres.

Clematis ‘Ville de Lyon’ (zones 4 to 9) is a long-time favourite of mine and produces carmine-red flowers in midsummer. It looks especially fabulous when allowed to climb through blue hydrangeas.

Clematis ‘Vyvyan Pennell’ (zones 4 to 9) is not everyone’s favourite, but it offers big, double light-violet flowers through June. One enthusiast aptly describes hers as “watered violet-blue silk decadence.”

Clematis ‘Hagley Hybrid’ (zones 4 to 9), a late-flowering hybrid with boat-shaped pinkish-mauve sepals, is a must-have. It is very easy to grow and should be on an arbour in everyone’s garden.

The self-seeding Clematis tangutica (zones 3 to 9) is one of the hardiest clematis I have come across. Once I even saw it growing on the west side of a house in Whitehorse! Its lemon-yellow pendulous blooms are produced from summer through late fall, followed by wonderful fluffy seeds that hang on all winter long.

With so many clematis species to choose from, no doubt every gardener has his or her top picks, but I hope you’ll be inspired to experiment a bit and try a few other worthy varieties. Perhaps you’ll even discover a new favourite of your own!

The following plants are hardy to the zone number indicated: • Clematis ‘Barbara Dibley’ – zone 4 • C. cirrhosa – zone 7 • C. ‘Dr. Ruppel’ – zone 4 • C. ‘Early Sensation’- zone 7 • C. ‘Hagley Hybrid’ – zone 4 • C. integrifolia – zone 3 • C. ‘Jackmanii’ – zone 4 • C. macropetala – zone 5 • C. montana – zone 6 • C. tangutica – zone 3 • C.‘Ville de Lyon’ – zone 4 • C. ‘Vyvyan Pennell’ – zone 4

David Tarrant of the UBC Botanical Garden is a well-known gardening expert, author, and host of Canadian Gardener on CBC television.