Secrets to growing a show-stopping clematis vine

FARGO — Clematis is called the queen of flowering vines for good reason. They’re the most prolific perennial flowering vines for the Upper Midwest, and when they’re in full bloom, they’re a beauty to behold.

I can’t imagine life without a clematis. I grew up with a tremendous purplish-colored Jackman clematis on the east side of my parent’s house in Lisbon, North Dakota. My wife, Mary, and I have followed suit and have four growing on wide trellises on the east side of our garage.

Michael Vosburg/The Forum

Clematis, whose plural can be either clematis or clematises, are easily recognized when they begin blooming in July. The deep purplish-blue Jackman cultivar is the most common, although there are other beautiful colors and cultivars, too.

Clematis aren’t difficult to grow, but there are definitely a few secrets that transform an average vine into a show-stopper, growing vigorously and covered with flowers.

Following are tips that, if followed, will create a clematis vine that completely fills a trellis.

• When planting a new clematis, expect it to take at least three years for the root and crown system to become robust enough to produce plentiful shoots to fill a trellis. Once in place, clematis rarely if ever need dividing, and should last many decades.
• The ideal location is the east side of a house, garage or other building, getting full morning sun, but shaded from the hot afternoon summer sun. Northern exposures might not provide enough sun, resulting in weak growth and sparse flowers.
• Clematis vines require the support of a wood or metal trellis. They won’t attach themselves to walls or solid fences without adding structures for the vines to twine around. For our own clematis, I attached 4-foot-wide chain-link fencing, hung vertically from our garage’s east side and spaced slightly away from the surface to allow vines to twine.
• One clematis plant can eventually cover a trellis 3 or 4 feet wide, but for a wider, denser presentation, plant two clematis 24 inches apart at the base of a four-foot-wide trellis.
• Clematis can climb at least 8 to 10 feet high.
• As the old saying goes, clematis enjoy their head in the sun and their feet in the shade. Short shrubs can be planted several feet away from the clematis to shade the roots, or annual flowers can be used to cast shade. This is especially important if an east exposure isn’t available and the clematis is on the south or west side.

• Clematis thrive in cool, moist, rich soil, as opposed to hot, baked clay. When planting, incorporate organic material such as peat moss or compost. Amending the soil is crucial, especially if the vine is planted along a foundation where the soil is packed and poor. If a clematis is already in place, organic material can still be gently mixed into the surface soil and surroundings.
• Mulch the base of the clematis with a 5-inch-thick layer of shredded bark, especially important on south or west exposures.
• Clematis are heavy feeders. Apply a cup of 10-10-10 granular fertilizer in May and again in June around the base of the vine and water in. Or mix 3 or 4 gallons of Miracle-Gro solution and apply every two weeks in May and June.
• Water regularly, giving a thorough soaking every seven to 10 days with a 5-gallon pail of water or more.
• Jackman clematis, and similar cultivars, bloom each summer on "new wood," which are the vines that grow during this current growing season. Each spring they grow back from near ground level.
• Allow the vines to remain in place over winter, then prune back to 6 inches above ground level in April. As the plants establish, each year they will send up more shoots arising from the root system, creating a broad clump instead of a solitary vine.
• Here’s a final tip that I learned many years ago that is relatively unknown, but it doubles the volume of vines and flowers. As the clematis vines begin new growth next May and are 6 to 12 inches high, pinch out the central growing tip of each emerging vine. Where there was one shoot, two will form. Each single shoot now becomes two, doubling the volume of vines and eventual flowers.
• Clematis will often reward its owners with a secondary lighter bloom flush in September.