|
ANSI A300 Pruning Standards
Crown Cleaning
This pruning includes the selective removal of dead, dying, diseased, crowded, weakly attached and low-vigor branches and water sprouts from a tree crown.
Crown Thinning
This pruning includes Crown Cleaning along with the selective removal of branches to increase light penetration and air movement into the crown of a tree. Increased light and air stimulates and maintains interior foliage, which in turn improves branch taper and strength. Thinning reduces the wind-sail effect of the crown and the weight of heavy limbs. Thinning the crown can emphasize the structural beauty of trunk and branches as well as improve the growth of plants beneath the tree by increasing light penetration. When thinning the crown of a mature tree, seldom should more than one-third of the live foliage be removed.
At least one-half of the foliage should be on branches that arise in the lower two-thirds of the tree. Likewise, when thinning laterals from a limb, an effort should be made to retain inner lateral branches and leave the same distribution of foliage along the branch. Trees and branches pruned in this manner will more evenly distribute stress throughout the tree.
Crown Reduction
This pruning reduces the height and/or spread of a tree. Thinning cuts are most effective in maintaining the structural integrity and natural form of a tree and delaying the time when it will need to be pruned again. The lateral to which a branch or trunk is cut back to should be at least one-half the diameter of the cut being made.
Crown Restoration
Improving the structure and appearance of trees that have been topped or severely pruned when heading cuts were made. One to three sprouts on main branch stubs should be selected to reform a more natural appearing crown. Selected vigorous sprouts may need to be thinned to a lateral or even headed to control length growth in order to ensure adequate attachment for the size of the sprout. Proper Crown Restoration may require several prunings over a number of years.
Crown Raising
Removing the lower branches of a tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas. It is important that a tree have a least one-half of its foliage on branches that originate in the lower two-thirds of its crown removed to ensure a well-formed, tapered structure and to uniformly distribute stress within the tree.
When pruning for view clearance, it is preferable to develop "windows" through the foliage of the tree rather than to severely raise or reduce the crown.
|