Spring Tree Pruning Tips

Saturday, March 26, 2011

John Campanini, GoLocalProv Landscape Contributor

Pruning is good for plants, trees, and shrubs. It helps control size, beauty, and health. It also helps renew or increase production. But it requires care.

To begin: when pruning, never cut more than 25 percent of a tree, shrub, or plant. Anything more endangers the plant’s survivability. Also, always use the right method and equipment to prune. Despite the benefits of pruning, there are times when you shouldn’t prune, like in the summer.

Descriptions of four pruning methods are below, with recommendations on when to use each method. These methods produce best results when done correctly. Also, make sure you have a clear objective in mind when pruning.

Heading Back controls size

It removes a branch up to a bud or lateral branch. Rhododendron, mountain laurel, azalea, winged euonymus and other plants with stout, single, or double trunks respond favorably to this pruning method. Use Heading back when new growth is complete.

Renewal removes old overgrown stems or canes

It involves eliminating one-third of the total stems or canes each year. Renewal produces a plant with entirely new top-growth every three to four years. Renewal also re-invigorates multi-stemmed plants such as spirea, forsythia, hydrangea, buddleia, and weigiela. This method works best in winter when plants are dormant.

Rejuvenation is renewal on steroids.

Instead of cutting a portion of stems annually, Rejuvenation cuts all of them at ground level in one season. Rejuvenation is the pruning technique of last resort. It promotes new shoots to sprout from latent buds that can be trained into nice plants. Rejuvenation restores poorly growing forsythia, hydrangea, privet, honeysuckle, lilac, boxwood, and spirea. Use this method in late winter or early spring.

Shearing shapes hedges into geometric forms.

Shearing produces hedges with narrower tops than bottoms. This allows sunlight to reach lower branches. Shear when new growth is complete.

Avoid Summer Pruning

Avoid pruning in the summer whenever you can. Plants, trees, and shrubs produce and store carbohydrates via photosynthesis in the summer. Pruning cuts away foliage from trees or shrubs, decreasing photosynthesis and depriving plants of life-giving carbohydrates. Another reason to avoid summer pruning is threats from pests. Fungi, bacteria, and insects are more numerous in the summer. Pruning gives pests access to vulnerable plant tissues through wood wounds. Pruning also releases volatile chemicals, as research shows, attracting harmful pests to trees, plants, and shrubs.

If you must prune in the summer, be prudent about it. Remove no more than 5-10 percent of total mass of live wood. This amount is well below the 25 percent threshold used as a guideline for annual pruning of healthy plants. Less is more in this case.

Pruning is good for trees, shrubs, and plants. It boosts health, attractiveness and survivability. Knowing when to prune is as important as knowing how to prune. While late winter-early spring is the best time to prune, summer is not a good time to prune. Prune with an objective in mind for best results. Also, make sure you use the right method and the right tools.

The Rhode Island Tree Council teaches proper pruning techniques in its Tree Steward’s Education classes. For more information, contact RITree at 764-5885, or go to RITree’s Web site.

John Campanini is technical director of the Rhode Island Tree Council. Previously, he was Providence’s city forester.

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