The Growth of White Clover (Trifolium repens) in Five Sown Hill Swards Grazed by Sheep

(1) The growth of white clover (Trifolium repens L.) was studied in five hill swards in mid-Wales, sown 10-39 years before with seed mixtures containing white clover and Lolium perenne L. and grazed by sheep. (2) The biggest reason for the increase in white clover ground cover between February and June (Simpson, Wilman & Adams 1987) was a near-fourfold increase in leaflet size. The peak period for leaflet size was around 21 June. (3) The clover appeared vulnerable to defoliation in early spring, with leaves very close together on the stolon and a lack of branch production. (4) The smallest differences between the five study areas were in rate of leaf emergence and leaflet size and the biggest differences were in the amount of branch stolon extension. (5) More leaves emerged on branches than on the stolon main axis during June, July and August, except on one study area where branching appeared to be inhibited by Agrostis tennis Sibth., acidity and aluminium. (6) Branch production and growth from recorded nodes were greatest where clover ground cover was increasing from a relatively low level. (7) The rate of stolon extension appeared sensitive to moisture supply. (8) Management to encourage vigorous white clover growth, therefore, would include providing both sufficient lime and sufficient moisture, controlling Agrostis, and avoiding both overgrazing in spring and undergrazing in summer. The development of varieties in which a higher proportion of nodes produce branches may be worthwhile.