Hardy Clematis that flourish on the Prairies

Photo by Brian Baldwin 'White Swan' was hybridized by Frank Skinner

Sara Williams
Saskatchewan Perennial Society
Clematis (from the Greek word for vine) are among our most beautiful vines. While many do very well on the Prairies with average care, others, such as the Jackmanii, need a great deal of coddling, coupled with your most protected micro-climate, and still may not survive our winters. On benches in garden centres and nurseries, they all share equal space. So how does one know if the plant you’re considering is ruggedly hardy or needs shelter? Begin with the Latin or botanical name – which should always be listed on the plant tag in italics.

The hybrids from Clematis alpina and Clematis macropetala (both native to China), are among the loveliest and toughest. They vary in height from 2.6 to 4 m (8 to 12 ft.) and climb by means of twinning leaf petioles, so allow space behind their supports for the leaves to do their job. Both species bloom on the previous year’s growth from late spring to early summer. The hybrid varieties of both species need little pruning unless they’re blocking a window or an arbor, usually every three or four years. They benefit from being planted in deep, organically enriched soil with a 10 cm (4 in.) layer of organic mulch at their base, and deep watering (to a depth of 45 cm/18 in.) every two weeks. Bloom is greater if the vine is in sunlight. These clematis are hardy, easy to grow and vigorous. No fuss, no muss.

The alpine clematis (Clematis alpina), native to the alpine slopes of Europe and Asia, was introduced to England in 1792. It has bell-shaped flowers in shades of white, pink or blue. Its compound leaves consist of three groups of three leaflets and twine around its support as it grows. They generally reach heights of 2 to 2.5 m (6 to 8 ft.). Among the cultivars are ‘Ruby’ with deep pink-dusty rosy red flowers; ‘Willy’ with pale mauve-pink flowers with a darker edge; ‘Constance’ with bright pink, almost red flowers; ‘Francis Rivis’ with larger deep blue flowers; ‘Pamela Jackman’ with rich, deep purple-blue flowers; and ‘Helsingborg’ with deep purple flowers.

The large-petaled clematis (Clematis macropetela) was first discovered in China by a French missionary, Pierre Nicholas Le Chéron D’Incarville, in 1742. But it was not introduced to Europe until just before World War I. It is slightly taller, generally between 3.6 and 4 m (10 to 12 ft.), with bell-shaped flowers. Many of its varieties have been developed by Prairie plant breeders such as Frank Skinner and Stan Zubrowski. Among the Skinner introductions are ‘Blue Bird’ with deep lavender blue flowers, ‘Rosy O’Grady’ with long dark pink pointed sepals, and the snow white ‘White Swan’. ‘Joe Zary’, honouring one of Saskatoon’s promoters of horticulture, has double purple flowers and was introduced by Stan Zubrowski of Prairie River. Other Clematis macropetala varieties include ‘Lagoon’ and ‘Maidwell Hall’ with blue flowers, and ‘Markham’s Pink’ with pink flowers. ‘Jan Lindmark’, a Scandinavian introduction, has dark bluish-pink flowers, while ‘Purple Spider’ has double purple flowers.

Quite different from all of the above are the hybrids of the herbaceous Clematis integrifolia and the climbing Clematis jackmanii. These begin growth each spring at ground level and climb to about 1-2 m (3-6 ft), blooming on the current season’s growth in late summer. Although the roots survive, the above-ground portion is killed to soil level each winter and must be pruned off in early spring. One of the best known of these is ‘Blue Boy’, introduced by Frank Skinner in 1947. A lovely blue, it blooms in late summer. A more recent introduction from Crimea, Ukraine is ‘Pamiat Serdta’ with light violet flowers.

Note: The golden clematis (Clematis tangutica) is listed on Alberta’s noxious weed list and is discouraged by the Native Plant Society of Saskatchewan because of its vigour and abundant self-seeding.

Retired from the University of Saskatchewan, Sara’s most recent book is Growing Fruit in Northern Gardens with Bob Bors. She’s been hosting garden tours for over 20 years – to Great Britain, Ireland, Europe, Turkey and Iceland. Join her for a tour of French gardens this September [Contact Ruth at 1-888-778-2378, www.worldwideecotours.com]

This column is provided courtesy of the Saskatchewan Perennial Society (SPS; saskperennial@hotmail.com ). Check our website (www.saskperennial.ca) or Facebook page (www.facebook.com/saskperennial) for a list of upcoming gardening events