   Pruning Coniferous Evergreens - October 24, 2007 Jeff Schalau, Associate Agent, Agriculture & Natural Resources, Arizona Cooperative Extension, Yavapai County Coniferous evergreens, such as pines, junipers, and cedars, usually require less pruning than broadleaf trees. They also grow differently than broadleaf trees and shrubs. Coniferous trees often have a dominant leader which causes them to be cone-shaped. This is especially true in young coniferous trees. Most pines, Deodar and Atlas cedar, spruces, Douglas-firs, and true firs are cone-shaped. Some conifers, like many mature broadleaf trees, develop a wide-spreading crown after forming a short trunk and have a diffuse, random branching habit. This diffuse branching pattern allows more latitude in pruning. The primary reason to prune trees and shrubs is to maintain health and vigor of the plant. Secondary reasons are to shape and to try to reduce the overall size. Pruning should only be done by experienced people that understand plant growth. In addition, working conditions should be safe and sharp, clean tools used. Large trees are usually best left to professionals. If in doubt, hire a reputable professional or ISA Certified Arborist. Dead, diseased, crowded, and structurally unsound branches should be removed first. Lower branches of conifer trees are often shaded out by the crown and die. Dead lower branches should be removed. Conifer trees can often have double leaders (forked tops) which are usually caused by damage to the terminal leader (the top of the tree). If possible, double leaders should be thinned to one unless the natural growth habit includes several main branches. The distribution of growing points often limits the severity of pruning conifers. In many conifers, all growth derives from buds formed in the previous growing season. These trees may have all their lateral buds in whorls just below the terminal bud (most pines), or lateral buds may be scattered along the shoot. Always prune conifers back to a visible lateral bud or branch. Unlike most broadleaf trees, most conifers do not have latent (hidden) buds that may initiate growth following injury. If there are no visible buds, pruning into old wood will usually result in a stub from which no new growth will arise. Luckily, most coniferous trees are sold with the lateral branches left intact and the crown extending all the way to the ground. The energy from these lateral branches will increase diameter growth and result in a sturdier tree. As the tree increases in height, these side branches can be pruned away. People often want to do this so they can enjoy the shade of the tree. Be aware that you should never remove more than 1/3 of the live foliage in a given year and it is better to remove as little as possible. The leaves are the food factory of the tree and help maintain vigor. To make a proper pruning cut on a large branch, do it in three steps. First, go several inches above the point where the final cut will be made and cut the underside of the branch about a third of the way through. Second, go above the undercut and saw through the branch. Third, make the final cut leaving the branch collar (the swollen area where the branch is attached). This method takes the weight off the branch first and prevents stripped bark where the final cut is made. Never use pruning paint or sealant on a pruning wound. Many landscapes contain juniper shrubs that have outgrown their allotted space, then they are radically sheared or stub pruned. This is not the way to correctly prune these plants. Follow the same rules outlined above: prune back to live lateral branches. For juniper shrubs, this may need to be done over the course of several years to maintain vigor and allow recovery. The best time of year to prune coniferous trees is in the fall and early winter. Cooler weather decreases metabolic activity yet, they have leaves year-round and continue to make food. Remember, pruning should always be done conservatively – especially if you lack experience. The University of Arizona Cooperative Extension has publications and information on pruning and tree care. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |