Column: Coniferous evergreens require less pruning
Originally Published: October 16, 2015 6:01 a.m.
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 cedars, 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. Safety is also a good reason to prune - especially around vehicular traffic and power lines. It is difficult to reduce the size of a conifer's size through pruning - it's best to select the tree to fit the location at the time of planting. 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 an International Society of Arboriculture (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, one of the leaders should be removed 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 originates from buds formed in the previous growing season. Conifer trees often have all their lateral buds in whorls just below the terminal bud. Always prune conifers back to a visible lateral bud or branch. Unlike 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.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 with greater trunk taper. 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 side 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 until it breaks away. Third, make the final cut preserving 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. When these are radically sheared or stub pruned, it can result in an ugly mess. 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. Conifer trees have leaves year-round and continue to make food. Remember, pruning should always be done conservatively - especially if you lack experience. Links to additional pruning information are included below.Follow the Backyard Gardener on Twitter - use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8992 or e-mail us at firstname.lastname@example.org and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.Additional Resources:How To Prune Coniferous Evergreen TreesUniversity of Idaho Cooperative Extensionwww.cals.uidaho.edu/edcomm/pdf/bul/bul0644.pdfA Guide to Successful Pruning, Pruning Evergreen TreesVirginia Cooperative Extensionpubs.ext.vt.edu/430/430-457/430-457.htmlPruning Trees: Shade, Flowering, and ConiferIowa State University Extensionwww.iowadnr.gov/portals/idnr/uploads/forestry/pruning.pdfJeff Schalau is the agriculture and natural resources agent for the University of Arizona Cooperative Extension, Yavapai County.