February 22, 2008

With last spring’s late freeze and last fall’s drought, people should hold off on winter pruning until plants and trees start to show signs of development because some may come out of dormancy with additional damage, said Richard Durham, University of Kentucky associate extension professor of consumer horticulture.

Typically, winter pruning is done between mid February and mid March after most of the severe winter weather has subsided, and it is just before spring – one of the busiest times for plant growth. However, because of last year’s unusual weather, people can wait to prune as late as the end of March to early April, Durham said.

“Regrowth is usually evident by early April as buds begin to swell and grow,” Durham said. “If parts of the tree or shrub are not showing renewed growth while other parts are, these sections are likely dead and will need to be pruned away.”

When most people think of pruning they think of their shade or fruit trees. However, for shade trees, pruning should mostly focus on correcting damage and promoting healthy growth. Dead branches, branches rubbing together or crowding the trunk are all reasons for pruning, he said. Thinning out diseased or unproductive branches to the tree’s trunk or major limb, improves the tree’s health, making it more open to receive additional sunlight and air movement. Heading back cuts, which remove only the terminal portion of a shoot, encourage the development of side branches and stiffen the remaining branch. This can be particularly useful for apple and pear trees, whose branches should be trimmed to support a heavy crop load.

Shrubs are pruned to maintain a certain shape or size. Flowering shrubs, like lilac and forsythia, should undergo rejuvenation pruning each year so the shrubs will flower more. This type of pruning removes between one-fourth and one-third of old growth each year and encourages new growth. For example, forsythia only blooms on recent growth while lilac can bloom on older growth, but more recent growth from the past 2-3 years is generally most productive.

It is important to not go overboard with pruning. While some trees are excessively pruned at the top because they encroach on utility lines, for the most part intensive pruning not needed and tree top pruning should be avoided. Painting or sealing cuts is not necessary and may actually delay the regrowth that helps the tree recover from pruning.

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