Dr. Leonard Perry, Extension Professor, UVM
Looking for an easy perennial vine that can grow in various situations, has a range of flower colors in both singles and doubles, and that provides a long flowering show in spring or summer? Consider the versatile clematis.
Although there are many other common names for clematis, the most common is “virgin’s bower.” Perhaps this was named for Queen Elizabeth I of England, the “virgin queen,” as it was during her reign that a popular species was brought to England from Spain. Yet, some say this name was used before her time, and instead comes from the German legend that this vine sheltered Mary and Jesus during their flight to Egypt. The word “bower” would fit this legend, as it comes from an old English word for dwelling, currently referring to a shady, leafy recess. The word “clematis” is from the Greek word for a climbing vine.
Clematis is often called the “queen of the vines” as the flowers are so attractive, in singles or doubles, and from one to five or more inches across. Some bloom early in the season, some later in summer. In warmer climates, or with some, they may bloom again in fall. Flower colors range from deep purple to shades of blue, mauve, pink, red, yellow, cream, white, and bi-colors. Generally they are flat, but a few are lantern-shaped. What we call the flower petals are actually and botanically modified sepals called “tepals.”
Although there are many species and cultivars (cultivated varieties), literally hundreds, that vary in their growing needs, most that you commonly find are hardy in USDA zones 4 (an average low of -20 to -30 degrees F in winter) through 7, or even warmer. Although some tolerate more shade (Jackmanii, Henryii, and Nelly Moser for instance), most need sites with at least six hours of full sun.
While their tops like part to full sun, a key to growing clematis well is keeping their roots cool. Remember the old saying, “tops in the sun, feet in the shade?” This can be done by planting in the shade of a small perennial or shrub (the vines will grow above it), or mulching. Watering during hot spells cools the soil too.
Best soil for clematis is a well-drained loam, with a neutral to slightly acidic pH. Water weekly during the first season, if there isn’t sufficient rain, and in subsequent years during droughts. Fertilize plants after planting with a plant starter fertilizer, or liquid seaweed or fish emulsion. In subsequent years, fertilize in spring with a granular organic fertilizer according to directions. Also each spring, add a shovel-full or two of compost around plants.
Another key, that you often see in catalogs and references, to getting the most bloom from your clematis is proper pruning. Many references list cultivars in three pruning groups or categories, depending on whether vines flower on stems from the previous season (group 1), both old and new stems (group 2), or just on current season’s growth (group 3). This is important in the sense that if you prune group 1 for instance in spring before bloom, you’ll be cutting off this year’s blooms.
If you need to reduce the size of the plant (they often get 10 feet or more high), or keep it more bushy and stimulate more flowers (such as group 2), prune in spring or early summer after bloom back to about one to two feet of growth. For those that bloom later in the season (group 3), prune these back in early spring when you see new growth. Don’t worry about getting the pruning wrong or making a mistake, as clematis are forgiving and at most you might lose a season’s blooms.
Unless you are growing clematis as a groundcover (such as the ground clematis species), they are best grown on some sort of support. As they attach themselves to supports by means of short leaf stems, supports shouldn’t be too wide—generally under a half inch. Thin-wire ornamental trellises work, if tall enough. Otherwise you can just use a fine-thread netting such as used for peas, wide-mesh fencing, twine, fishing line, or even twigs. By using these you can grow clematis on sides of walls or around lamp posts, or let them ramble up through shrubs.
Since clematis may take a few years to reach maturity and full blooming potential, it’s best to start with plants from nurseries already a couple years old. Choose ones in quart or preferably gallon pots. Work plenty of compost into the soil prior to planting. Then, be careful when planting as stems can be broken easily. Make a wide planting hole, and plant slightly deeper (2 to 3 inches) than they were in the pot. You can plant potted vines any time between spring and early fall.
Planting several different varieties almost guarantees you a continuous sweep of color from spring to the first hard frost. You may find several species and quite a few hybrids bred from them, some being classics dating back to the 1800s. Early flowering (pruning category 1) include the single Nelly Moser (pale pink with carmine midstripe), ‘Duchess of Edinburgh’ (white with yellow stamens), or the double Belle of Woking (silvery mauve).
Popular ones flowering later in the season on current year’s growth (pruning category 3) are ‘Ernst Markham’ (red with gold stamens), Perle d’Azur (single pale blue with purple midstripes), ‘Hagley Hybrid’ (single pink), ‘Jackmanii’ (rich purple single), or ‘Comtesse de Bouchaud’ (single rose pink).
Then there are those that often bloom early and late, on both old and new growth (pruning category 2). ‘Lincoln Star’ is an attractive bi-color with raspberry flowers edged white. ‘Elsa Spath’ is a prolific bloomer, producing lots of lovely single blue-purple flowers. In this same group, blooming from mid-summer into fall with lantern-shaped yellow flowers is the Chinese species known as Golden Tiara. It is followed by attractive silvery, fluffy seedheads. Another Chinese species that has lantern-shaped flowers, but lavender-blue, is the downy clematis. It blooms in early spring, and often again in fall.
Keep the basics of growing clematis in mind—at least half day of sun, cool roots, well-drained soil, and proper support—and you should be rewarded with many years of blooms.