Clematis may occasionally be infected by a distinctive disease called slime flux, characterised by a whitish, smelly ooze coming from the stems. Fortunately, it may be possible to save affected plants.
What is clematis slime flux?
Clematis slime flux is a bacterial problem that can affect most clematis species. Damaged areas of stem are colonised by bacteria, leading to wilting, dieback and the appearance of a foul-smelling exudate from the stem. The disease can be fatal, but plants can sometimes be saved by the pruning out of affected parts.
Slime flux symptoms can also develop on the stems of a wide range of other trees and shrubs.
Clematis: clematis slime flux develops when a damaged part of the stem becomes colonised by bacteria that normally reside harmlessly in the soil or on the stem surface. Any factor that injures the stem can lead to the problem developing, for example;
- Frost damage
- Pest feeding
- Any type of mechanical damage (including strong winds twisting the stems)
- Even natural growth cracks
- Infection may also sometimes occur through the root system
The bacteria penetrate deep into the stem tissues, and when the sugary sap rises in spring this is fermented by the bacteria to produce the foul-smelling slime. Gasses are also produced which force the slime out under pressure and may result in further stem splitting. A range of bacterial species, as well as other organisms such as yeasts and fungi, are often found within the slime, all taking advantage of the sugars within the sap.
Other trees and shrubs: slime flux and a similar disease called bacterial wetwood are also found quite frequently on the stems of a wide range of trees and shrubs. The biology is similar to that of clematis slime flux, although it is thought that in trees the bacteria most usually colonise the plant through the roots. Weeping and fluxing from patches on the trunk is often the only symptom, but branch dieback may occur.