Clematis wilt is a fungal disease of clematis, particularly the large-flowered hybrid cultivars. The fungus causes rapid wilting and, in severe cases, can kill the whole plant.
Common name Clematis wilt
Scientific name Calophoma clematidina (syn. Phoma clematidina, Ascochyta clematidina)
Plants affected Clematis spp.
Main symptoms Rapid wilting and death
Caused by Fungus
What is clematis wilt?
Clematis wilt is a disease of clematis caused by the fungus Calophoma clematidina (syn Phoma clematidina, Ascochyta clematidina). Many of the large-flowered hybrid cultivars are very susceptible, but the smaller flowered species appear to be much more resistant.
Wilting has long been recognised as a serious problem in clematis. Although it is known that Calophoma clematidina causes clematis wilt, there are many cases of wilting recorded where the fungus is not present. Research has clarified two important points:
Wilting in large-flowered hybrid cultivars may be caused by Calophoma clematidina, in which case it should be possible to find some of the symptoms described below
Wilting in resistant hybrids and species clematis is very unlikely to be C. clematidina, and is probably caused by environmental problems
So, although wilting in clematis plants is often blamed on the fungal infection, unless it affects one of the more susceptible large-flowered hybrids it is most likely to be caused by environmental problems. Even on large-flowered hybrids, wilting of shoots is often the result of other problems such as pest (e.g. slugs and snails) or physical damage.
Clematis is a plant which, in the natural environment, prefers a deep and fertile soil in a moist and shaded habitat. However, in gardens, clematis are often planted in shallow dry soils in exposed sites, often close to buildings. In such circumstances they suffer from root stress which contributes to poor growth and what is loosely described as wilt. Overall, infection by C. clematidina is a problem for the nursery trade and specialist growers, but relatively uncommon in gardens.
The symptoms of fungal infection and environmental stress can be similar. The following symptoms are associated with fungal infection:
When fungal infection occurs through the leaves, these wilt and the leaf stalks turn black. Leaf infection is followed by rapid wilting of the stems
Fungal infection can also occur through stems. Freshly affected stems show black discolouration of tissue when split open
Young healthy shoots may be produced from the base of affected stems, sometimes from below ground
Try to create a suitable root environment by deep cultivation and mulching, to minimise root stress
If fungal infection is suspected, cut out all wilted stems back to healthy (non-stained) tissue and promptly destroy the affected material to prevent it contaminating the soil. New healthy shoots may be formed at ground level
Disinfect pruning tools to prevent spread of spores and avoid transferring infected plant and soil material to a new area
Particularly susceptible cultivars include: Clematis ‘Henryi’, ‘Vyvyan Pennell’, ‘Mrs N. Thompson’, ‘Duchess of Edinburgh’, ‘William Kennett’, ‘Marie Boisselot/Madame le Coultre’, ‘Ernest Markham’. Clematis 'Comtesse de Bouchaud'; C. 'Jackmanii' and C. 'Nelly Moser' are also susceptible
Resistant cultivars and species include: Clematis ‘Avant Garde’, ‘Bonanza’, ‘Confetti’, C. alpina, C. montana, C. orientalis, C. viticella (which is tolerant rather than resistant), C. integrifolia, C. macropetala, C. tangutica
There are no chemicals available to treat clematis wilt.
Calophoma clematidina can survive in the soil on dead plant material and organic matter. Infection occurs when spores are splashed or otherwise carried to leaves or young stems. Infection spreads to the shoots and stems (which, when split open, are stained black inside) and causes rapid wilting and death. The root system is often not killed and young shoots frequently regenerate from or below ground level. The disease is not immediately fatal, but infected susceptible cultivars will usually die eventually.