Saturday, October 31, 2009

American National Standard, ANSI A300-2001

American National Standard, ANSI A300-2001 "Standard Practices for Trees and Other Woody Plant Maintenance" guidelines - Part 1 Pruning.

Some ANSI pruning standard practices include:
  • Not more than 1/4 of the foliage on a mature tree should be removed within a growing season.
  • When a branch is cut back to a lateral, not more than 1/4 of its leaf surface should be removed. The remaining lateral should be large enough (at least 1/3 the diameter of the removed parent branch) to assume apical dominance. In other words, a large lateral will suppress excessive sprouting. 

  • Thinning should result in an even distribution of branches on individual limbs and throughout the crown. Ignoring this concept leads to over-lifting (excessive limbing-up) which weakens a tree by making it top-heavy, and lion's-tailing which puts the weight load on the ends of the branches, making branches more prone to break-outs in high winds.

How Much to Prune?
  • Not more than 1/4 of the tree’s foliage should be removed per year.
  • Leave 1/2 foliage in bottom 2/3 of tree.
  • Keep tree’s natural shape.
  • Well pruned tree won’t look pruned.

Utility Pruning - Urban Trees:
  • No topping. Only pruning methods approved by this spec.
  • Minimum number of pruning cuts.
  • Remove branches at laterals not at pre-established clearing limit.
Things to keep in mind:
Pruning should take into account the species of tree, the site limitations (parking or building clearance) and other extenuating circumstances in deciding what or how much to prune. A tree that has been neglected for many years may require several years of pruning to reshape it and some drastic cuts may be required. It is better to train trees when they are young in order to avoid the severe pruning consequences later.

The bottom line is communication is critical. Make sure that Con Ed's consulting arborist conveys (in writing) exactly what will be pruned. Don't assume that the worker with the saw knows what he is doing. Insist that a Certified Arborist is onsite supervising the work at all times.

We want to ensure that Con Ed's crews prune cautiously and wisely to protect the quantity and quality of our urban forests.

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