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How to Prune a Tree - A Graphic Tutorial

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Important Tree Pruning Method #1 - Crown Thinning
Crown Thinning

Tree Crown Thinning

USFS
Crown thinning is a pruning technique primarily used on hardwood trees. Crown thinning is the selective removal of stems and branches to increase light penetration and air movement throughout the crown of a tree. The intent is to improve a tree's structure and form while making life uncomfortable for tree pests.

Stems with narrow, V-shaped angles of attachment (graphic b) often form included bark and should be selected for removal first. Leave branches with strong U-shaped angles of attachment (graphic a). The included bark forms a bark wedge when two stems grow at sharp angles to one another. These ingrown wedges prevent strong attachment of stems often causing a crack at the point below where the branches meet. Removing one or more of the stems will allow the other stem(s) to take over.

Branches growing off these stems should be no more than one half to three-quarters of the diameter of the stem at the point of attachment. Avoid producing "lion's tails" or tufts of branches and foliage at the ends of branches by removing all inner lateral branches and foliage. Lion's tails can result in sunscalding, epicormic sprouting and weak branch structure and breakage. Branches that rub or cross another branch should be removed.

To avoid unnecessary stress and prevent excessive production of epicormic sprouts, no more than one-quarter of the living crown should be removed at a time. If it is necessary to remove more, it should be done over successive years.

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