The Influence of Summer Pruning and Cropping on Growth and Fruiting of Apple

Abstract

Abstract Trees of apple [Malus domestica Borkh. cvs. Jonathan/Malling (M) 26] were summer-pruned each August from 1978-1980 by heading all shoots longer than 10 cm, and their response was compared to trees receiving only a light dormant-pruning by thinning-out cuts. Cropping treatments were a full crop or defruiting in June. Final length of shoot regrowth on summer-pruned trees was 82% and 76% less than terminal growth of control trees in 1979 and 1980, respectively, but terminal shoots produced the year following pruning were 55% and 62% longer on summer-pruned tress than on controls in 1979 and 1980, respectively. Summer-pruned trees with a full crop had 13% shorter terminal shoot length than defruited trees in 1979, but cropping had no effect in 1980. Trees with a full crop had a smaller annual increase in trunk cross-section than defruited trees, but were not affected by summer pruning. Summer pruning restricted tree canopy dimensions, resulting in 43% less canopy volume than control trees in 1979 and 1980, increased canopy openness to light penetration, and hastened flower opening. Pruning treatments did not affect fruit set. Fruit yield per tree was reduced by summer pruning, but yield per canopy volume was not affected. Fruit size was decreased by summer pruning in 1979 but was increased in 1980. Fruit soluble solids were reduced by summer pruning in 1979 and 1980, fruit color was increased in 1978 and 1980, but not in 1979. Flesh firmness was unaffected by summer pruning.