Botrytis cinerea, the pathogen causing grey mould,at first inhabits dead plant material, but it is also capable of infecting healthy plant tissue. Grey mould first manifests itself in the form of soft, damp patches, which develop into a light grey mycelium. This disease spreads through the air by means of conidia and remains viable in diseased plant parts and plant remains. Grey mould is a very common disease affecting numerous plant genera and species; it causes damage especially in moist, dense plant communities, where there  is insufficient air circulation.

Damage caused by grey mould among geranium rooted cuttings. The cuttings of many other ornamentals are also susceptible to grey mould, e.g. fuchsias, chrysanthemums and potted roses.