Tips for choosing, trimming trees

Published on March 20, 2013 with No Comments

If you have questions about trees, here’s a list of tips on tree care excerpted from a study on managing urban forests prepared for the City of Milton.

Step 1: Choosing a tree
Select a good specimen. Look for a single stem/trunk with few low lateral branches. Avoid trees that fork within five feet of the ground. For species such as redbud and dogwood, this can be difficult, but it’s not impossible.

Step 2: The first two years
Keep pruning to a minimum. Leaves are the “factories” that manufacture the food for a tree to grow and recover. However, remove dead, broken or damaged limbs, and prune as needed to maintain a central “leader” for the tree.

Step 3: Years 2-5
Now is the age to prune in earnest. Encourage the central leader by removing any co-dominant stems and any lateral limbs which may be growing upright rather than outward.
Retaining some lower limbs will help protect the lower trunk so it can strengthen and taper. A good rule of thumb is that lateral branches should always be smaller than the trunk by at least half. Bigger lateral branches can threaten the main trunk.

Often at this stage, people prune with a mind to make the tree look good now rather than considering what’s best for the tree’s long-term success. They may be reluctant to remove unfavorable limbs because they don’t want the tree to lose its fullness. This is a mistake which often results in retaining limbs that are too low or create V-crotches that provide immediate fullness. However, retaining them may result in the loss of the tree’s central leader. It’s better to take a long-term view of what’s best for the tree.

Step 4: Years 5-10
People tend to neglect trees at this age, but it’s a critical time. Co-dominant stems can easily develop higher in the canopy and damage the leader’s progress. Remove low, temporary limbs before they get too large.

Remember the mature height and spread of the tree. Removing branches 7 to 9 feet up may be adequate for a dogwood, but not at all suitable for an oak that may ultimately grow to be 70 feet tall.

Step 5: Beyond 10 years
The purpose and species of a tree is important to consider. For example, the lowest limbs of an oak on a residential street may need to be at least 20 feet high while a dogwood in a garden may need to be only 3 feet from the ground.

Permanent limbs should always be smaller in diameter than the trunk at their point of attachment. Select scaffold limbs that grow at a wide angle from the tree; 50 to 90 degrees is best.

Trees that tend to have weak structures:
Silver maple
Red maple
Green ash
White ash
Chinese Elm cultivators
Ornamental pear (especially Bradford)

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