ALGAE - Primitive plants that form a green film on surfaces which are more or less constantly damp. Although the presence of algae on the trunk of a BONSAI>BONSAI>BONSAI can impart a feeling of age it is generally considered to be unsightly. If left unchecked algal growth can build up to a comparatively thick, bright green coating which can harbour fungal spores and small insect pests. Careful application once per year of a proprietary winter wash (tar oil or similar) diluted to half strength should be sufficient to keep it in check. Good ventiliation especially under winter protection, will also help.