Three major diseases afflict the clematis. The good news is that two of them, leaf wilt and powdery mildew are seldom fatal to the plant. The bad news is that the third disease, slime flux, almost always kills the plant. Fortunately, the most common diseases are leaf wilt followed by powdery mildew, while slime flux is a rarity. Protect your clematis from disease by promptly clearing away dead foliage on or around the plant; growing it in moist but not soaking soil; and positioning it where the foliage gets plenty of sun but the roots are in shade.
Things You’ll Need
- Cut out wilted areas back to the healthy parts of the clematis if leaves suddenly droop then wither. The condition is most likely clematis leaf wilt, also called leaf and stem spot. Destroy the parts of the plant that you remove by burning. Leaf wilt can kill all the growing parts of the plant but does not affect the roots, so the clematis often grows back.
- Treat leaves and stems with a proprietary fungicide if they develop a white, powder-like covering, which is the signature of powdery mildew’. Follow the fungicide manufacturer’s instructions when applying. Plants often make a full recovery.
- Dig out the whole plant and the soil around the roots if the leaves wilt and a bad-smelling, pink-to-orange slime starts to ooze from damaged parts on the main stem. These are signs of slime flux, a disease that is usually fatal to the plant. Bacteria feeds on sap spilling from damage to the bark and fermentation causes the slime. Burn the plant after removal and move the soil from around the roots away from growing plants.
Tips & Warnings
If your clematis is growing in a container, replace the top 2 inches of soil with new potting compost each spring.
Check a clematis plant carefully when buying from a garden store. Make sure the foliage is a healthy green, rejecting plants that show signs of drooping or withering.