Abstract: The TRISTAR expert system (TRIangular STrAtegic Rules for British herbaceous vegetation) is a PC‐based consultancy tool designed to help bridge the gap between academic plant ecology and practical vegetation management. It is a ‘what if facility, for use by students, naturalists, conservationists, planners, administrators; indeed anyone with an interest in environmental science and management, conservation or reconstruction of herbaceous vegetation. The system is written in Leonardo 3 (Creative Logic Limited, Uxbridge, UK). Release I of TRISTAR deals with the fundamental environmental and management processes which control the composition of British herbaceous vegetation. The system takes a specification of initial steady‐state vegetation, asks the user to specify an altered environmental and/or management scenario, and predicts the composition of a new steady‐state vegetation in terms of plant‐strategic types. The high‐level approach through plant strategies makes it possible to construct a very robust rulebase despite a lack of hard information in many areas of understanding.