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Clematis: Floral beauties of the garden

Clematis grows over an arbor.

“Concealed were all thy beauties rare

’Neath the dark umbrageous shade,

But still to gain the loftiest spray,

Thy weak stem its efforts made;

Now, every obstacle o’ercome,

Thou smilest from thy leafy home.”

– “The Clematis,” Alexander Bathgate, in “Far South Fancies,” 1890

Alexander Bathgate (1845-1930) was a Scottish lawyer, journalist, conservationist and poet who often wrote about his adopted home of New Zealand. His poem “The Clematis” pays homage to C. paniculata, or “puawhananga” in Maori, the most common of seven native species of clematis in New Zealand.

This week, I, too, want to pay tribute to clematis, a sprawling genus of woody and herbaceous perennials in the Ranunculus (buttercup) family that can be found in all temperate regions of the globe. I have three nonnative species growing in my garden in Medford, two of which have already bedazzled me with their showy floral displays in early and midspring.

C. armandii, or evergreen clematis, is a woody vine with leathery foliage that puts out sprays of white, star-shaped flowers in March. My highly floriferous C. montana var. rubens covers an arbor in my backyard during May with large, pale pink flowers and lime green stamens. I also have a pretty lavender-flowered Japanese cultivar, which blooms later in the summer.

In fact, there are more than 250 known species and thousands of cultivars of clematis, which take their name from the Greek “klema,” meaning “climbing vine.” Depending on the species, clematis flowers have between four and eight “petals” that are actually sepals (modified leaves) surrounding contrasting-colored stamens. Clematis became popular in Europe and America as a garden plant in the 1800s. Widely hybridized in Victorian England, clematis became associated with mental beauty in the “language of flowers.”

Clematis is known as the “queen of the vines” among plant enthusiasts, for good reason. However, not all clematis species are vining plants. I recently visited Italio Gardens and Nursery in Medford where owner Baldassare Mineo showed me his collection of herbaceous clematis in the non-twining Integrifolia group. These bush-type clematises produce nodding, urn-shaped purple flowers from late spring to fall, depending on the cultivar.

There are 12 different classifications of clematis: evergreen, alpine, macropetala (downy clematis), montana, rockery, early large-flowered, late large-flowered, herbaceous, viticella, texensis, orientalis and late mixed species. The Gardener’s Path website provides a useful description of each of these classifications at gardenerspath.com.

There are about 30 species of clematis that are native to North America. These include C. ligusticifolia, C. columbiana, C. texensis and C. crispa. Although the flowers often are less showy than nonnatives, native clematis are disease-resistant and tend to play nicely with other plants in the garden.

Each type of clematis falls into one of three pruning groups. Group 1 consists of the early bloomers (winter to midspring), such as my C. armandii and C. montana. They produce flowers on shoots from old wood, so they should only be lightly groomed after flowering. Heavy pruning is not needed.

Group 2 includes early, large-flowered cultivars that produce blooms on old wood for the first flush of flowers, then on new growth for a second flush of flowers in late summer or early fall. These clematis should be pruned in early spring as new buds emerge by lightly cutting back up to one-third of the stems to a pair of buds about 12 inches from the ground. To encourage a second flowering, prune again after spring flowers have faded.

Group 3 are the late large-flowered clematis like my Japanese cultivar and the herbaceous clematis. They produce flowers on new growth during the current season, so they should be pruned back hard in late winter or early spring (or simply allow the plants to die back on their own and then remove the debris in spring).

According to Ashridge Nurseries of Somerset, England, there are five important considerations for successfully growing clematis: preparation, depth, water, temperature and first pruning.

Find a place in your garden where the clematis will have at least six hours of sunlight. They like well-draining soil with a pH around 6.0 to 6.5. Vining species will need a trellis or other support. Dig a hole that is twice as wide and deep as the root ball and place the plant so the crown is about 3-4 inches below the surface of the soil. Add bone meal and compost to the planting hole, fill, water thoroughly and mulch.

Be sure to keep clematis moist, particularly as it’s establishing in the garden. My mature clematises do not require a lot of water. Some gardeners say clematis are heavy feeders, but I only add fresh compost and mulch annually, and they seem to do just fine.

I’ve learned one of the most important aspects of growing clematis is to keep their roots cool and allow the vines to grow toward the sun. One of my C. armandii is unhappy in its container because the soil heats up in the late-afternoon sun. I need to move the pot to a spot on my patio where it won’t receive as much direct sunlight but the vines will get the sunshine they need to bloom profusely.

After any type of clematis is planted, cut it back to 6-12 inches tall during the first growing season to encourage branching and a bushier plant. Afterward, follow pruning recommendations for your specific clematis group.

Some gardeners recommend planting a groundcover or other plant around the clematis to shade its roots, which has the added benefit of hiding what English gardener and author Christopher Lloyd famously called the clematis’s “bad legs.” Other gardeners, however, claim so-called companion plants might choke out establishing clematis roots, and some mature clematis can grow aggressively and overpower other plants in the garden.

Despite this warning, clematis often are grown effectively around the base of trees where they are allowed to climb up the trunk, or they’re planted beneath a shrub and allowed to twine through the branches.

We are fortunate to have the Rogerson Clematis Garden in West Linn, about 270 miles north on Interstate 5 from Medford. The garden is a nationally accredited collection of clematis with more than 2,000 individual plants. Garden curator Linda Beutler wrote “Gardening With Clematis” (2004), the go-to book about growing healthy, happy clematis in our garden.

I’m not sure if Alexander Bathgate was an expert on clematis, but he was certainly enthralled with the New Zealand native. He wrote of C. paniculata:

“Fair crown of stars of purest ray,

Hung aloft on Mapau tree,

What floral beauties ye display,

Stars of snowy purity …”

Rhonda Nowak is a Rogue Valley gardener, teacher and writer. She founded the Bard’s Garden in Central Point. Learn more at literarygardener.com; email Rhonda at Rnowak39@gmail.com.