Released July 24, 2009
COLUMBIA, Mo. — While most pruning of apple trees takes place during winter, additional pruning in the summer can be an effective way to manage young apple trees, said a University of Missouri horticulturist.
“Summer pruning is primarily used to control unwanted growth and to establish a central leader tree structure during the year of planting and the subsequent two years,” Michele Warmund said.
Such pruning involves pinching off young, competing lateral shoots in the upper portion of the central leader. This directs growth into a single shoot and keeps the leader dominant, she said.
A dominant central leader provides the narrow, pyramidal shape of the tree and minimizes shade in the lower portion of the canopy.
Pruning too early in summer can spread fire blight, a bacterial infection of apples and pears, she said. Summer pruning should not take place before late June, when the threat of fire blight is past.
Pruning mature trees in summer reduces tree height and allows more light into the canopy to improve fruit color.
“Summer pruning of mature trees should be done after terminal bud set,” she said. “If pruned earlier, multiple shoots appear near the cuts.” Excessive early wood removal may delay flower bud initiation for next year’s crop.
For early-maturing cultivars like Jonathan and Red Delicious, summer pruning is only recommended in late July. For late-maturing cultivars such as Red Fuji, Winesap, York and Granny Smith, pruning is only recommended during the four weeks before harvest.
Warmund notes that summer pruning may reduce fruit yield and sugar content as shoots are removed from the tree.
Summer pruning cannot remedy excessive crowding and should not substitute for correct spacing of trees at planting.
For more information, see “Summer Pruning Apple Trees” in the July 2009 issue of Missouri Environment & Garden (Vol. 15, No. 7), available online at http://ppp.missouri.edu/newsletters/meg.
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http://extension.missouri.edu/news/DisplayStory.aspx?N=471
Source: Michele R. Warmund, 573-882-9632
Writer: Robert E. Thomas, 573-882-2480, thomasr@missouri.edu
