Bur Oak, Quercus macrocarpa
Basalt Town Hall, Photo: Lisa DiNardo 9-22-11
WHY: Remove dead, diseased and crossing branches, improve trunk and branch structure and access pruning: limbing up for pedestrian or vehicular access.WHEN: Live branches are best pruned in the dormant season or following a flush of growth after the leaves harden and turn dark green. However, if pruning is necessary follow these precautions; root growth is slowed temporarily when live branches are removed in summer and since most root growth occurs during the growing season removing large numbers of live branches during the summer is ill advised unless your objective is to slow growth. Light pruning (less than 10%) can be performed safely on most species at any time. Some research suggests that pruning during the summer results in less stem decay than dormant-season pruning (ISA,1994). However, more research needs to be done before suggesting summer as the best time to prune.
HOW: Pruning should be done with an understanding of how the tree responds to each cut. Improper pruning can cause damage that will last for the life of the tree, or worse, shorten the tree's life. Always make the cut to the outside of the branch bark ridge (raised area of bark tissue in the union of two branches or two stems or in the union of branch and stem) or stem bark ridge (raised bark in the union of two stems). The branch collar (a swelling at the base of a branch where it joins the trunk or larger branch resulting from overlapping trunk and branch tissue) contains trunk or parent branch tissue and should not be damaged or removed. Do not cut the collar. For larger branches, its weight should first be reduced. This is done by making an undercut about 12 to 18 inches from the limb’s point of attachment. Make a second cut from the top, directly above or a few inches farther out on the limb. Doing so removes the limb, leaving the 12- to 18-inch stub. Remove the stub by cutting back to the branch collar. This technique reduces the possibility of tearing the bark.
An Illustrated Guide to Pruning, Edward F. Gilman
A New Tree Biology, Alex L. Shigo
Trees Are Good - International Society of Arboriculture (ISA)
Resources
A New Tree Biology, Dr. Alex Shigo (Father of Modern Arboriculture)
Pruning Mature Trees, International Society of Arboriculture (ISA)
Pruning Young Trees, International Society of Arboriculture (ISA)
Prepared by Lisa DiNardo, Horticulturist/Certified Arborist, RM-7161A
Town of Basalt Public Gardens and Community Forestry Department
