1. The fruit yields of the strawberry varieties Talisman and Redgauntlet, growing at Invergowrie, Scotland, were increased, sometimes substantially, by cutting and removing the foliage in August, soon after completion of the previous harvest. Increases of yield were inversely related to the yields of untreated control plants, and varied from fourfold when the yield of control plants was low to 10% when the controls yielded nearly 2 lb. of fruit per plant.
2. The increased yields resulted from the formation of more fruit trusses per plant, and dissections in one year (1959) showed that this was mainly due to the formation of trusses in a larger proportion of the crowns.
3. The additional fruit trusses were initiated either soon after defoliation, or several weeks later when a new leaf canopy had formed.
4. Defoliation is thought to increase truss induction by removing the source of a vegetative-growth-promoting, flower-inhibiting hormone.
5. Wherever truss formation is deficient and thereby limiting the fruit yield of unmown plants, as in these experiments, post-harvest defoliation is recommended as a corrective.