Dear Mira:

Thanks for contacting the UVM Extension Master Gardener Helpline about your clematis. You report that your usually very healthy clematis now has leaves close to the ground that are darkening in color and drying up and that one small stem close to ground has leaves turning bright yellow. You wonder if this is a fungus problem.

The most serious clematis fungal disease is clematis wilt, a stem rot/leaf spot disease caused by the fungus, Ascochyta clematidina. This disease mainly affects large-flowered clematis hybrids. Species clematis and small-flowered hybrids are more resistant. What kind of clematis do you have?

Large Flower Clematis Hybrid

If you have a large flower hybrid, it may have clematis wilt. Infection can occur through the leaves, causing leaf spots. Leaf veins often develop a purple coloration. Affected leaves may then shrivel and the leaf stalks turn black. Leaf infection is followed by wilting of the stems. The plant also can be infected directly through the stems, which show black discoloration of tissue when split open. Affected vines wilt suddenly and then die, often just as the flower buds begin to swell. One or more stems of the diseased plant may be affected or all above ground parts of the plant can be killed down to just below the soil level.

If your plant shows signs of fungal wilt, you should cut the dead vines at ground level, remove them, and either burn them or put them in the trash. Be sure to disinfect any tools or pruners you use with a bleach solution to prevent contamination and to avoid transferring infected plant and soil material to a new area.

Clematis wilt rarely kills the entire plant. Affected plants usually send up new shoots. Often, an affected plant will recover after a year or two.

Species Clematis or Small-flowered hybrids

If you have a species clematis or small-flowered hybrid, it is unlikely that the wilting is from clematis wilt. It is probably caused by cultural problems, other diseases, or feeding damage from invertebrates. On any clematis, wilting of shoots is often the result of problems such as grazing of the stems by slugs or snails (sometimes chipmunks) or simple physical damage, such as twisting of stems in strong winds. Both hybrid and species clematis can also be affected by root diseases such as Phytophthora root rot and honey fungus, which interferes with the root system function and causes wilting.

We attach links to informative resources about clematis and diseases that affect them.
https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/insects-pests-and-problems/diseases/cankers/clematis-wilt

https://yardandgarden.extension.iastate.edu/how-to/growing-clematis-iowa

https://www.rhs.org.uk/disease/clematis-wilt

We hope that this information is helpful. If you have additional questions, please feel free to contact us.

Good luck!

Pat