As of December 2020 Trees and Shrubs Online contains nearly 11,000 individual articles on woody plants hardy in the northern temperate zones. The texts are derived from three major sources: the Eighth Edition of Bean’s Trees and Shrubs Hardy in the British Isles (1970s) together with the Supplement (1988); New Trees: Recent Introductions to Cultivation (2009); and brand new text specifically commissioned for TSO.
Many groups are still in their Bean format, some combine text from Bean, the Supplement, and from New Trees, and as funding is secured to commission revisions these are brought up to date. The following list identifies the major groups that have been fully updated so far, and a list of those groups currently being re-written is given below.
The following genera are currently being finalised ahead of editing and publication during 2021: