Thoughts of spring

Thursday, March 19, 2020

We’ve been enjoying a few days of warm weather lately and that means people are out cleaning up yards or shelter belts.

If your thoughts are turning to pruning, please consider these ideas before you prune or hire an arborist. Keep two things in mind when considering large tree pruning.

First, each tree species takes on a characteristic shape and form because of its genetic makeup and local environment. Pruning may change its appearance temporarily, but not permanently.

Appreciate the natural growth form of each species and try to enhance this when you prune. Second, pruning of any kind places some stress on a tree by removing food producing leaves, creating wounds that require energy to seal, and providing entry of disease.

This doesn’t mean you shouldn’t prune. It means you should do it only when you have a good reason and then do it carefully and wisely. Pruning should help the tree!

When to prune trees. Pruning of dead branches can be done at any time of the year since you do not cut into any live tissue.

For all non-flowering trees, pruning is best in late winter before the buds start to swell. The second best time is mid-summer which allows for better shaping and dead limb removal as the leaves are on. For flowering trees, it is best to wait after they flower to prune as pruning in late winter may remove all of the flowering buds.

Pruning in summer should be moderate or slight in order to discourage excessive sprouting and loss of food production due to removal of foliage. It is always better to prune a tree-in-need at any time of the year then to leave it unpruned.

Types of pruning. Several types of pruning may be necessary to maintain the health and attractiveness of a tree. Cleaning is perhaps the most obvious type of pruning. It involves the removal of dead, dying, diseased, and low-vigor branches from the crown of a tree. Thinning, another technique, is the selective branch removal. Thinning, improves the structure, light penetration, and air movement through the crown.

Raising a third method of pruning, removes the lower branches from a tree to provide clearance for buildings, vehicles, pedestrians, and vistas. Another type of pruning, reduction, reduces the size of the tree. Reducing a tree’s height or spread is best done by pruning back the leaders and branch terminals to secondary branches. When done properly, reduction helps maintain the form and structural integrity of the tree.

Quite the opposite method of pruning is topping. Don’t top trees. Topping is often the most harmful tree pruning practice known and is never recommended.

Topping is the removal of major portions of a tree’s crown by cutting the branches to stubs (Figure 1). Topping reduces the tree’s food production, creates large wounds that invite disease, and destroys the natural growth habits of the tree.

Topping is by far the most expensive form of tree pruning in the long run. A topped tree will require continual attention and follow up treatment for the remainder of its life. Also, the value of a topped tree will be significantly decreased, whereas the value of a properly pruned tree will only increase with time.

For more information on tree pruning, contact Lee Schmelzer, the Stillwater County Agriculture and Natural Resource Extension Agent at 322-8035. Additional information on tree pruning can be found in these resources: Pruning Deciduous Trees by Robert S. Logan and Steven B Larsen, MSU MontGuide MT199304AG; Pruning and Trimming Your Trees, Dr. Peter Kolbb, MSU Extension Forester; Pruning Fruit Trees in Montana, Cheryl Moore-Gough and Robert Gough, MSU MontGuide MT 199215AG.

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