CABI’s Plantwise programme runs local plant clinics in 24 countries across Africa, Asia and Latin America where trained ‘plant doctors’ provide on-the-spot diagnosis and advice for farmers who bring samples to the clinics. A database that records each consultation and shares knowledge across clinics and countries continually builds the ability of the programme to respond to farmers’ needs. The programme embodies key principles of an innovation systems approach. Systems diagnosis, building networks and linkages, balancing supply push with demand pull, strengthening the role of intermediaries, and experimenting and learning are among the features which ensure the programme continually evolves to meet emerging needs and challenges. As well as providing a valuable service to smallholder farmers, enriching their ability to address production constraints, the sharing of lessons among stakeholders is having a positive overall effect on national plant health systems.