Thinning and heading cuts
Summer pruning involves using mostly thinning cuts—cutting the current year’s growth all the way to its branch collar. A heading cut is the partial removal of a branch—not to the branch collar of the current or previous year’s growth. Heading cuts are used in the winter to stimulate side branches lower on the branch.
Many plants need seasonal pruning to look good. Shrubs and perennials which bloom in mid- to latesummer form their flower buds after a summer pruning, before going dormant in the winter. Left unpruned, each season’s growth gets further-and-further from the plant’s center and the plant soon looks rangy and ugly. If the crown’s foliage was too rangy this past summer, don’t spare the pruning shears. Thin back the crown after bloom. (Some heading cuts may be useful.) The more you prune the crown back, the denser it will be next summer.
Like a good comedian; timing is everything with……..summer pruning. Prune too early in the summer, and the growth may act like a dormant pruning— forcing growth. Prune too late in the summer, and any new growth is vulnerable to early hard frosts and winter’s deep freezes.
Once the new growth has naturally slowed down due to heat and reduced water, summer pruning is more effective. In the arid west, the gardener can expect a noticeable tapering off of new growth by mid- to late-July. (If you water too much, you’ll provoke plenty of growth.) However, new growth can continue at a rampant pace well into July during a mild summer. In contrast, the warm, rainy summers of the Midwest can maintain active growth until fall. For guidance, ask local gardeners or the Cooperative Extension Service. When trying to restrain a vigorous tree or shrub, pruning is best done in the summer (to continue thinning out unwanted growth). Some pruning all season long is best for a balanced approach to caring for trees, shrubs and perennials.
This doesn’t mean I’ve cast aside all winter pruning. Winter pruning invigorates a tree, stimulating new growth. Thus, there is almost always a place for winter pruning with my trees. I use winter pruning to stimulate side shoots where there are bare areas in the tree’s branches, cutting back tall, unbranched young trees to help form side branches exactly where I want them by forcing a new side shoot to grow in any desired direction by cutting to just above a bud which faces the preferred orientation.