One day your clematis vine is thriving and ready to flower. The next day it’s withering before your eyes. What happened? Chances are it’s a fairly common fungus that affects clematis plants, called clematis wilt.
What Does Clematis Wilt Look Like?Clematis wilt is a fungus disease (Ascochyta clematidina) that is sometimes called clematis leaf and stem spot. Clematis wilt causes the foliage and stems to dry and whiter, possibly turning black. You may see reddish lesions along the stems, but the onset and spread of clematis wilt can be quick. You may not have any warning before an entire clematis vine turns brown. On the other hand, it’s not unusual for only a few stems to be affected.
What Causes the Disease?Clematis wilt is spread by spores. Like most fugal diseases, is more prevalent in damp or humid weather. Plants that are tangled and remain wet well into the day are even more prone to attack.
On older clematis plants, the woody portion near the ground is often the first area affected. The plant dies back because the fungus cuts off its circulatory system and no water can be carried through the plant. Left untreated, clematis wilt will spread throughout the plant and can kill a heavily infested plant.
What to Do for Affected PlantsClematis plants can recover from wilt, because it does not attack their root system.
At the first sign of withering or drying, cut the affected stems back to ground level. It sounds severe, but it can save your plant. Dispose of the cuttings somewhere other than the compost. New shoots should emerge from the base shortly, although Washington State University Extension’s fact sheet said “One resource on this subject states that renewed shoots can appear up to three years after the problem, so do not lose heart if this happens.”
Keep the roots water, even if there is no top growth. Remove all remaining growth in the fall and dispose of it. The fungus can over-winter in the dead foliage.
If you wish to use a preventative fungicide, sulfur is recommended.
Are All Clematis Susceptible to Clematis Wilt?To some degree, yes. The larger flowered varieties are most prone and the some of the smaller flowering varieties, like Clematis alpina and Clematis viticella, show better resistance. There is also some evidence that the older and better established a plant is, the less likely it is to become infected.
- Clematis Leaf and Stem Spot (or Clematis Wilt), WSU Extension
- Growing Clematis, Ohio State University Fact Sheet HYG-1247-94