Nothing irks me more than to see a tree improperly pruned. Well, improper planting and no watering of new trees irks me too, but I’ll save that for another time. Today I’d like to focus on the basics of tree pruning and next month I’ll talk about utility line pruning. Being a hands-on person it’s usually easier for me to show how-to rather explain how-to but I’ll try. There’s just so much to explain about the subject that there are text books and day-long seminars specifically dedicated to tree pruning so bear with me.
First, it is important to acknowledge that pruning is the intentional wounding of a tree to accomplish a specific objective. Pruning removes tree parts, mainly branches but sometimes a portion of the trunk. The result is an open wound of exposed wood but more significantly, the loss of live wood, buds, fruit and leaves. This is important to know because trees store food or energy (in the form of sugars and starches) throughout the entire tree, from the tips of the roots to the tips of the leaves. When we remove live parts, we are reducing a tree’s ability to 1) make more food for itself and 2) tap into that stored food source when needed. A tree operates as a closed system; each part (root, trunk, branch, bud, fruit and leaf) depends on the other part. When we disrupt or remove or damage a part, it affects the entire system. Resources (water, food, hormones) within the tree have to be converted and reallocated to compensate for the damage and loss. This is why removing too much live wood can and does send a tree into shock. The result is either a vigorous sprouting of shoots or the beginning of an overall decline in tree health, depending on age, vigor, site conditions, etc.
Second, we should prune only to accomplish a specific objective. According to the International Society of Arboriculture’s Best Management Practices Guidebook for Tree Pruning (revised 2008) pruning objectives include: reduce risk of failure (breakage, improve branch structure), provide clearance (street, sidewalk, sight-line), maintain health (deadwood removal, crossed or rubbing branches) and improve a view (garden, pond, mountains). Whenever anyone asks me “When or how should I prune my tree?” my answer is “Why do you want to prune?” If they then have a blank stare and nothing to say in return I know they need some direction. A lot of folks fall into the “monkey see, monkey do” syndrome. Just because their neighbor had a tree pruned they think they should as well. If you feel compelled to prune, please consider the why before the how. A few minutes of thought may just save you some time to go do something fun instead. If you’re not sure or need assistance, contact me and based on my schedule I’ll do my best to help you.
Third, make the correct cut. Once you’ve figured out your pruning objective, it is important to cut in the proper place. If you know what to look for, a tree will tell you where to cut. If cutting a branch where it is attached to the trunk, find the branch bark ridge and the branch collar before raising the saw. The branch bark ridge (BBR) forms at the crotch where the branch meets the trunk. In most hardwood trees it forms a distinctive ridge of bark on the upper side between the two parts. The branch collar (BC) is located on the underside where the branch meets the trunk. Just as shirt collar wraps around your neck, the BC wraps around the branch. It is formed by the layering of trunk and branch wood each year and generally forms a slight bulge under the branch. If you can’t see it, you can usually feel it. This sounds weird, but if close your eyes and run your hand along the branch base you’ll be able to detect it. Just don’t let the neighbors see you groping the tree. A proper cut should be made just outside of the BBR and the BC. If you cut too close or too far way, the tree won’t close-over the wound properly. Pruning live wood can be done any time of year but is best accomplished in the winter months so the spring trunk wood can begin to grow around the wound. Arboriculture studies have shown that pruning paint, tar or spray is not effective against decay fungi nor will it benefit the tree. If you do not like the look of the exposed wood, use a can of gray or brown paint for aesthetics although it is best just to leave it be.
Fourth, when pruning, less is more. The best pruning jobs are those that look like nothing has been done. That is to say, the tree has not been disfigured (see topping, below) or too much removed. In general, it is best not to remove any more than one-quarter (1/4) or 25 percent of the canopy in any one year. If that much has been removed it is best to skip a year or so before pruning again so as not to over-stress the tree. Remember you are wounding the tree, removing stored food and reducing its food-making capacity. In addition, pruning small diameter limbs is better than large limbs. A tree can grow over and close a smaller wound faster than it can a larger wound. This is why young tree pruning is important and should be performed if pruning objectives dictate. A large wound can take decades for the tree to close over. In the meantime, decay fungi work their way into the wood cells and can spread into the interior of the tree. Unfortunately, this is the case with many of our mature trees in town, both public and private. Interior decay can sometimes lead to a reduction in structural strength, but that’s a subject for another article.
Fifth, topping is an unacceptable, outdated and barbaric method of pruning. Topping is otherwise known as buzz-cutting, rounding-over, flat-topping, etc. It is the indiscriminant and random cutting of branches and the trunk. This takes no skill or thought. Please don’t ever pay anyone to prune in this manner. If they don’t know any other way of pruning, call me and I’ll help them. For those of us who consider crape myrtles a tree, it is painful to watch this butchery happen to an otherwise nice flowering tree. I’ve already seen this ‘crape murder’ (as it is often referred to) happening around town. Some folks do this because of the “monkey-see” syndrome, some do it because that’s how their relative always did it and some folks do this because they think it makes the tree bloom more. If you happen to fall into one or more of these categories and would like to lessen your work load this year, please give me a call.
Sixth, pruning deadwood should be taken care of as soon as possible. Because the wood is dead, it is no longer functioning or providing any benefit to the tree. Therefore, it is OK to remove it any time especially if it is near or over a roof, driveway, play area, pool, etc.
Lastly, please do not attempt to climb a tree with ropes or spikes or climb a ladder with a chainsaw or prune a tree whose limbs are near the electric lines! Please do always wear eye protection, gloves and if using a chainsaw, wear safety chaps and a hardhat. Stay tuned for utility line pruning next month but in the meantime, visit our website at www.cityofcamden.org and click on Residents and then Tree Pruning to view tree pruning photos and illustrations.