Growth and Flowering of Vigorous Apple Trees as Affected by Summer or Dormant Pruning1

Abstract

Summer pruning of ‘Starking Delicious’, ‘Golden Delicious’, or ‘Stayman’ apple ( Malus domestica Borkh.) trees in mid-August (about 14 weeks after full bloom) did not suppress shoot growth the following year, as compared to similar pruning prior to budbreak in early April. ‘Stayman’ trees pruned in June had more regrowth than those pruned in August. A 1% naphthaleneacetic acid (NAA) solution applied to the summer pruning cut prevented regrowth. The increase in trunk and branch circumference was reduced by August pruning, as compared to dormant pruning. Summer pruning did not influence total bloom the year following treatment, but summer pruning for 2 consecutive years reduced the amount of bloom on 2-yr-wood. Cutting to the first spur on 2-year-wood in August did not suppress shoot growth the following year as compared to heading back to 4 leaves on current season's wood.