A List of Clematis Varieties that Are Resistant to Wilt

What Is Wilt?

• Wilt has plagued clematis growers for over a century, but there's still no consensus as to its cause. When wilt strikes, a fungus known as Phoma clematidina impacts the stems of the affected plant. There remains a great debate on whether the fungus causes the wilting or simply capitalizes on a weakened stem. Either way, the result is the same. The vine's stems suddenly collapse, preventing the plant from taking up water. Foliage quickly turns black. Often the attack comes on young, newly planted plants in full leaf and blanketed with buds. One stem or many may be involved, but wilt remains localized and doesn't move throughout the plant. Many times, infection begins at the site of a minor injury to a stem.

Susceptibility and Resistance

• Spring-blooming, large-flowered clematis hybrids exhibit the greatest susceptibility to wilt. Most of these highly susceptible hybrids can be traced back to breeding programs in the late 1800s that relied heavily on two particular clematis types. Species clematis and their cultivars demonstrate the most resistance to clematis wilt. Small-flowered hybrids and late-blooming, large-flowered hybrids also show good resistance. Species clematis tend to be smaller-flowering, however the plants have more abundant blooms and longer bloom times that more than compensate for the smaller blossoms. Depending on variety, clematis vines can be hardy in U.S. Department of Agriculture plant hardiness zones 3 through 11.

Resistant Species and Cultivars

• Many clematis species show high resistance to wilt. They include Clematis viticella, Clematis texensis and Clematis integrifolia, all hardy in USDA zones 4 through 11, along with Clematis alpina, Clematis macropetala and Clematis montana, all hardy in USDA zones 4 through 9. Cultivars of wilt-resistant species generally exhibit similar resistance to the disease. Several cultivated varieties warrant special consideration for outstanding resistance to wilt. Among them, "Huldine," a late-blooming vine with 5-inch white flowers, earned the Royal Horticultural Society's Award of Garden Merit. "Avant Garde" offers striking 2-inch flowers with velvety red petals surrounding rose-pink pom-pom centers. Blue Angel clematis, another Award of Garden Merit winner, bears 6-inch, lilac-blue flowers on a heavy-flowering, vigorous vine. All three of these wilt-resistant cultivars are hardy in USDA zones 4 through 9.

Prevention and Recovery

• Many clematis experts suggest that wilt problems may often be due to environmental factors rather than disease. Clematis vines prefer deep, fertile soil and a moist, shaded location -- contrary to what many residential plantings provide. Failure to provide proper siting and culture for a vine causes stress and symptoms similar to clematis wilt. The right location and care prevent many problems. If clematis wilt does strike your vine, don't be discouraged. Prune out affected stems as far back to the roots as possible. Remove and destroy all infected stems and foliage, including any fallen leaves. Water thoroughly, drench the plant with a systemic fungicide and be patient. It may take a season or two, but vines usually recover and often return more vigorous than before.