Flowering and Shoot Extension in Heath Plants of Different Geographical Origin

(1) Plants of Calluna vulgaris, Erica cinerea and E. tetralix collected from a wide range of sites (mostly British, but including one from Spain) were grown in experimental plots in Stirling. Flowering was observed from 1972 to 1975 and shoot extension was measured in 1974. (2) In Calluna and Erica cinerea late flowering tended to be associated with a warm, southerly site of origin, and early flowering with a cooler, northern site of origin, while in E. tetralix early flowering was associated with a prostrate growth form and small shoot increments. (3) In all three species the date of flowering was positively correlated with the date at which shoots reached 50% of their maximum extension, whilst in Calluna and Erica cinerea plants with a rapid rate of extension tended to originate from cooler and more northerly climates.