Clematis wilt

Calophoma clematidina

The sudden collapse of a large-flowered clematis: a healthy shoot wilts from the tip almost overnight, with a dark lesion at the base of the wilted stem.

Fungus Serious Rain splashAirborne spores Spreads to neighbors

What you'll see

A shoot, or the whole top of the plant, wilts and blackens suddenly in late spring or summer, often just as the buds are about to open.
The leaf stalks droop and the leaves darken from the edges, while the roots stay perfectly healthy.
Look at the base of a wilted stem for a dark, sometimes cracked lesion where the fungus has girdled it.
The collapse is fast — a vigorous plant can flag within a day or two.

Why it happens

A fungus that enters the stem, usually low down near soil level, and forms a lesion that girdles it and cuts off the water supply above. Spores splash and blow onto the foliage and stems from infected debris.

Warm, wet spring and early-summer weather brings it on; the large-flowered hybrids are far more prone than the small-flowered species.

Treating it

Cut every wilted stem right back to healthy tissue, or to below soil level, and bin or burn the prunings.
Water and feed the plant well, as an established clematis usually sends up fresh healthy shoots from the base.
Do not dig the plant up — the roots are rarely affected and will recover.
Clear away all fallen leaves and stem debris that could carry the fungus.

Keeping it away

Plant clematis deep, with the crown a good few centimeters below the soil, so spare buds sit safely underground.
Choose the tougher small-flowered species and viticella types, which rarely wilt.
Keep plants unstressed with a cool root run, a mulch and steady watering.
Clear fallen foliage each autumn and keep the stem base free of rotting debris.

Who gets it

Large-flowered clematis hybrids most of all; the small-flowered species such as viticella and montana are far more resistant.

Clematis