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 phenomenon 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.