In trials on Cambridge Favourite over 9 years plants with adjacent shelter had increases of 20-26% in the numbers of leaves, crowns, trusses and runners. Yields from sheltered and exposed plots were 10-23 and 7-22 t/ha, respectively, the yield from sheltered plots exceeding that of exposed plots each year by 2-7 t/ha. The reasons for these effects and the value of shelter are discussed.