Clematis wilt disease causes clematis plants to wilt rapidly – in a matter of hours. The leaves and leaf stalks turning black (not brown) is the main symptom. When the leaves turn brown, this is more characteristic of clematis powdery mildew disease or physical damage to the stems.
Clematis wilt disease mainly attacks large-flowered, summer-flowering varieties. Early- and late-flowering species and their varieties are rarely affected.
Most suspected cases of wilt disease are actually caused by physical damage to the stems. Clematis stems are very brittle and easily damaged. Once this damage occurs, water can’t be carried from the roots to the top of the plant, which then wilts.
Another cause of wilting is infection from the bacterial disease clematis slime flux.
Whether wilting is caused by the disease or by stem damage, providing the plant is otherwise strong, new shoots should be produced from the base of the plant or from below ground level. Repeated attacks from the disease will weaken the plant and may eventually kill it.