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Laidback Gardening with Robert Kourik

Laidback Gardening with Robert Kourik

Summer Pruning

Wanna get a tan while pruning fruit trees? Wanna spend less time pruning altogether? Then summer pruning is for you. The control of shoot growth summer pruning offers means there is far less pruning in the winter. You’ll be able to prune in a tee shirt (and other clothes please) in more comfort.

For “Popper” (my Grandpa – I have no idea how we came up with his nickname), tree pruning, especially fruit trees, was exclusively a winter task. “The trees will bleed too much if you cut them in the summer”, was the prevailing wisdom. In my youth, I never questioned his word. But as I got older and spent more time gardening, I noticed that wind storms in the summer damaged limbs as much as winter’s ice, sleet, wind and snow. So, I reasoned, nature must be used to healing the damage—the “pruning cuts” of any season.

Then I ran across an amazing outof- print, 1919 book entitled California Fruits, by Edward Wickson. Inside I found this intriguing passage–”…fruit bearing is promoted by pruning after the chief growth of the season is attained. Summer pruning to check the too exuberant wood growth [what are called suckers and water sprouts by many gardeners] of some kinds of trees is employed…where the vegetative [leafy] process…seems fairly to run riot…..”

From another favorite old text, The Pruning Book, by L. H. Bailey, 1911, I found an answer to “Popper’s” concern about trees bleeding—”Fruit trees rarely bleed to any extent, and on trees which do bleed, it is doubtful if any injury follows.” Walnuts and certain ornamentals, such as elms and maples, will bleed when pruned in the summer, but with no harmful effects.

My experience with fruit trees has proven the efficacy of summer pruning. Over the past 40 years I’ve learned: If you prune too early in the summer, the effect is much like winter pruning—new side-shoots will form and growth will be stimulated. Wait to prune until the burst of spring and early summer growth has tapered off. Summer pruning is the best way to control rampant growth such as so-called “water-sprouts” and “suckers.” It has a mild dwarfing or stunting effect, but is not debilitating. Still, it’s hard to tell if summer pruning stimulates more fruiting; in spite of Wickson’s assertion. I prune my plum trees exclusively in the late summer (late August), after the harvest if I can, to control any growth that is too vigorous. Summer is also the best time to remove leafy growth which is overly shading the tree—resulting in slow ripening and poor fruit color.

Summer pruning’s shortcomings

Foremost, summer pruning is a new concept to many. Pruning trees in leaf makes it harder to see a tree’s branching pattern. The main and secondary limbs may get sunburned. (When pruning in hot summer areas, cut with discretion, leaving enough foliage to protect the main trunk and upper branches.) With fruit trees, some fruit may be knocked off if you prune on older limbs before harvesting.

Summer pruning can curtail disease

Summer pruning effects the balance of nitrogen in the plant’s tissue which helps form sturdier shoot growth. Healthy growth is more resistant to powdery mildew. Powdery mildew infects apple, pear, plum and prune trees and rose bushes. In California, experience has shown that a schedule exclusively of spring pruning can encourage powdery mildew. By not forcing succulent growth with dormant pruning, this disease may have a harder time getting a foothold. Although, fungicides are much more effective than pruning in controlling mildew.

Cytospora canker, bacterial gummoisis, and bacterial canker can be reduced by the summer pruning. These three prominent diseases can also enter through pruning wounds when it rains, especially those made in late winter through early summer.

Avoid these troublesome diseases with summer pruning. (Disinfect the clipper’s blade with 10% bleach between every cut.) Some diseases enter open pruning cuts. The fungus Anthracnose spp. causes cankers and enters cuts during fall rains in the west—don’t prune too late in the summer, allow plenty of time for a callus to form.

If you have an abandoned tree, it’s best to use mostly summer pruning to “rehabilitate” it—and you’ll save time. (Paid gardeners often instinctively prune only in the winter With all the subsequent rampant growth, it gives them job security.)

Make modern cuts

As with all modern pruning, cutting flush to the limb or trunk is no longer advised. The safest way to prune requires identifying two parts: the branch collar and the branch bark ridge. The branch collar often has a slightly swollen base or shoulder-shaped lump where each shoot, branch, or limb is attached. (Conifers usually have a prominent branch collar.) Prune to leave the branch collar intact.

Can’t spot the branch collar? Don’t cut leaving a long stub which can be colonized by diseases and fungi which may subsequently enter the heart of the branch or trunk. Use the branch bark ridge to determine the best cut. Use the illustration as a guideline for a proper cut.

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.

Summer pruning for shape and bloom

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.

When to summer prune

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.