Archive for Sunday, February 7, 2010

Prune fruit trees now to improve summer crop

David Vertacnik explains his tree-pruning technique.

February 7, 2010

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The apple tree in the backyard really needs some attention, and despite the cold, late winter is the best time to give your fruit trees a little tender loving care.

David and Wendy Vertacnik, owners of Vertacnik Orchard, 1403 East 1850 Road, Lawrence, started pruning their apple trees a few weeks ago. In average northeast Kansas winters, David recommends waiting until after the first of the year to start pruning to ensure trees are in full dormancy, but says it is important to complete the job before the trees begin actively growing again in the spring.

Vertacnik's recommendation for how much to prune from an apple tree is my favorite. "The tree has to be open enough to throw a cat through the tree," he says, as he assures me that he does not check his work with actual cats. The analogy is important, though, because many gardeners fail to prune enough from their fruit trees.

Fruit researchers suggest removing about one-third of the total amount of wood from an apple tree each year. Peach trees can be pruned to one-half, while pear and plum trees should only be pruned lightly by heading back branches or thinning minimally.

Structural pruning of fruit trees is especially important because trees need to be strong enough to support the fruit they produce. Some varieties - Vertacnik lists the Red Delicious apple as an example - naturally grow with narrow branch angles that are weak and easily break with a heavy fruit load.

Although several pruning techniques are acceptable for fruit trees, Vertacnik recommends developing a framework for strong horizontal branches. If this is unachievable with pruning, use spacers. Vertacnik makes his own spacers with short 1-inch-by-1-inch blocks of wood. He drives finishing nails into each end of the blocks, cuts off the heads of the nails, then places the block in the crotch where two branches come together. His goal is to spread the angle between the two branches to 30 degrees or more.

Since the Vertacniks have more than 100 trees to take care of, they get a head start on the pruning season by marking branches with white latex paint after all the leaves have fallen in late autumn and early winter. David attaches a brush to a long handle so that he can reach everything from the ground, then walks the rows looking for branches that need to be "edited."

"Sometimes I just say, 'That guy has to go,'" Vertacnik says. "Fruit needs light to get good size, and to develop better color. Opening a tree up also lets more air move through." Increased air circulation reduces the occurrence of disease in susceptible fruit tree varieties.

Vertacnik also recommends starting with the largest branches when removing limbs. He says it helps to avoid overpruning, and small branches that need to be removed will be more obvious once the big ones are gone.

The Vertacniks added seedling peach trees to the orchard last spring and will begin pruning them when the apple tree pruning is complete. Developing good branching structure when a fruit tree is young saves work as trees mature, although all fruit trees should be pruned every year to stimulate production and reduce disease.

For the young trees, Vertacnik says, "At this point, I just want to establish four laterals that will become dominant branches."

For homeowners thinking about planting a fruit tree, the Vertacniks recommend selecting disease-resistant dwarf or semi-dwarf varieties but suggest that dwarf varieties should be staked.

Get out and prune your fruit trees but try not to hurt the cat.

  • Jennifer Smith is the Douglas County Extension Agent - Horticulture for K-State Research and Extension. She can be reached at 843-7058.

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