Mechanical Summer Tipping of Tart Cherry

By Charles D. Kesner
Professor Emeritus
Department of Horticulture
Michigan State University

There are only two times (under Michigan conditions) when side hedging should be done to gain maximum beneficial effects. The first is during the bloom period. Generally this would only be done ONCE IN THE LIFE OF AN ORCHARD, and that would be if you had a seven or eight-year-old block of trees that had never been hedged before. This hedging should not be too severe. One of the most common mistakes I see is the tendency to cut too deeply. The standard timing for mechanical summer hedging is a period ranging 2 or 3 days on either side of 45 days after full bloom. It should be emphasized that timing is critical in terms of response when hedging tart cherries. Bloom and/or summer hedging 45 days after full bloom produces an entirely different effect than dormant hedging or even post harvest (August or September) hedging. Hedging at the right time promotes shoot and spur development back inside the tree and, therefore, good yields of quality fruit which are much less susceptible to wind damage. Hedging at the wrong time produces a thick wall of brush on the outer surface of the tree, and this inhibits flower bud production due to shading.

As already mentioned, there is always a temptation to hedge too deep. In doing a one-time bloom period hedging, try to form a fruiting wall without making drastic cuts. Simply lay the cutter bar in at the top so that what you are removing is the "belly" about half way up the tree and very little in the top and bottom portions. When hedging 45 days after full bloom, set the cutter bar so that 10 to 50% of the CURRENT SEASON'S GROWTH is removed. Try never to go into two-year-old wood.

Another mistake we often see is making the side hedging cut almost straight up and down. The sides need to be tapered in at the top to take maximum advantage of the sunlight; about a 60 degree angle is probably the most beneficial. Mature tart cherry trees hedged straight up on the sides will be shaded much of the day, and you have gained nothing by hedging.

Dormant hand pruning is also necessary: Our data indicates that mechanical summer hedging of tart cherries 45 days after full bloom is not dwarfing but rather simply changes the direction of tree growth. In fact, total growth on summer hedged trees usually exceeds that of dormant pruned trees. At the same time, summer hedged trees produce more spurs and flower buds per unit area. The extra lateral growth produced as a result of summer hedging can form a relatively thick area in the outer 18-24 inches of the tree. THEREFORE, IT IS ABSOLUTELY IMPERATIVE THAT ENOUGH LIMBS BE REMOVED FROM THE TOP CENTER OF THE TREE DURING THE DORMANT SEASON OR AFTER HARVEST TO ALLOW FOR LIGHT PENETRATION IN THE CENTER OF THE TREE. This requires hand pruning, which, in our experience, only takes a few minutes per tree.

Revised June 1990

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Last Revised: 3-5-99