A growth stage key for winter linseed (Linum usitatissimum)

Summary. A growth key for use in winter linseed Linum usitatissimum is described. The decimal key is based upon the principles outlined by the BBCH scale. This scale covers the following main development stages in winter linseed: germination and emergence, leaf development, basal branching, stem extension, inflorescence development and emergence, flowering and capsule formation, development of the seed and capsule, capsule and seed ripening and stem senescence. These are subdivided into secondary stages. The key aims to provide farmers and advisers with clear guidance on appropriate growth stages for treatment of winter linseed crops and its' use is discussed with particular reference to agro‐chemicals. Botanical illustrations are presented, based on samples taken from winter linseed crops covering the main growth stages.