TREE TRIMMING & PRUNING

The definition of “crown-thinning” is the removal of a conservative amount of secondary branches (not any major limbs) evenly throughout a tree — typically 25-30% of the canopy. A more aggressive crown-thin can sometimes be justified for only the hardiest of tree varieties. For your average shade tree, crown-thinning is the most basic yet important type of pruning. How frequently this should be done ranges from about twice per year to once every few years, depending on the tree variety and the individual tree.

The best way to judge whether a tree is due for a crown-thin is to look up into the canopy — rather, to look THROUGH the canopy — to see how much of the sky is visible through the foliage of the tree. If it is so dense that one cannot hardly see any of the sky beyond the tree, crown-thinning is definitely recommended. WHY? Because if you cannot easily see through a tree’s canopy, then there will be a lot of resistance to wind, just like the sail on a boat. This is mainly a problem if a storm comes through, and then all one can do is hope for the best. The Arizona monsoon season is known to be accompanied by microbursts that unpredictably strike certain areas with particularly strong winds. Proactive tree care will avoid a canopy that is overly dense, so as to minimize the chances of broken limbs or even loss of the entire tree. If a tree’s foliage is growing very densely, there will also likely be crossing branches which will tend to rub against each other with normal shifting (as caused by wind or other forces), and as they grow the limbs will cause wounds at points of contact that worsen over time. A good Certified Arborist will be mindful of crossing branches — or branches that will eventually cross — while performing a crown-thin. Other more minor issues that a basic crown-thin will help with is shade. With more sunlight allowed through to the grass or other plants growing under a large shade tree, you can hope for a healthier lawn or shrubs that would otherwise be too shaded. A Certified Arborist can help save you money in the future by bringing such issues to your attention before they get harder to fix.

Crown-reduction is the correct way to make or keep a tree smaller. Crown-reduction means shortening many of the secondary limbs around the outside of the canopy using proper reduction cuts. The best application of crown-reduction is when a tree has been planted in a small area. It isn’t uncommon for a sapling tree to be planted with little to no consideration given to how large it may eventually become — which varies depending on the species as well as environmental factors (such as watering and soil quality). Mindful planning of the potential sizes of various tree in a yard is tricky, and if mistakes have been made, crown-reduction can help with overcrowding in the yard. Some trees are kept small purely for artistic reasons as well. A bonsai tree is the extreme example of the growth, the size of a tree, being severely scaled back. Similar to crown-reduction is structure clearance, which is reduction of foliage away from (or also raising over) buildings, power lines, sheds, fences, pools, or anything else where overgrowth may potentially cause property damage or inconvenience. Whether the concern is pests, pool filters, boundary fights with neighbors, or large limbs dropping onto the newly tiled roof, structure clearance will likely be needed on a regular basis for best results as the tree grows. The earlier a future conflict is foreseen, the easier it is to “train” a tree to grow a certain way (i.e. to promote vertical/horizontal growth, to stay clear of telephone lines, etc).

Crown-cleaning is simply removal of unsightly dead branches. Removal of deadwood is has both aesthetic value and safety considerations — dead branches are ugly, and they may eventually be shed (which is of course problematic for large limbs over homes, carports, or where people or pets often walk underneath). The most common time of year for crown-cleaning is during the Springtime after there have been hard frosts — ficus and sissoo are especially vulnerable to frost damage, as well as any tropical tree variety. For deciduous trees, it can be hard to determine what is dead and what is merely dormant during the Winter season; in the Spring and Summer months, after the trees have leaved out again, deadwood will be more apparent. Another way to tell dead from living is by scratching away some of the bark to see if it is green underneath (possible on ficus, bottle trees or other varieties with thin, waxy bark). For thin branches, pliability is an indication of being alive; if a twig does not easily bend but is so brittle that is snaps, it is dead. In cases where a tree has a lot of deadwood, a Certified Arborist can help you judge whether a tree is in a state of decline because of age or because of environmental factors (i.e. watering and soil quality). Sometimes measures can be taken to prevent further decline, such as fertilization or more consistent deep-watering. Otherwise, complete removal might be necessary for a tree that cannot be salvaged or is already completely dead.

Subordination corrects the specific problem of codominance. Codominant leaders, whether in multiple trunks or in major branches higher up, are called codominant because they are similar in diameter. The crotch between them will typically be V-shaped (instead of the ideal U-shape). The problem with a tight V-shaped crotch is that there may eventually be included bark at the union of the two codominant branches, which weakens the crotch until eventually each major leader grows heavier and heavier and they actually split apart. The larger the tree, the more danger the problem poses to the tree itself (as well as the people or animals living nearby). Codominant trunks with included bark is especially problematic in places where the splitting of a big, heavy portion of the tree could cause expensive damage to cars or homes, or injury to people or pets. If severe codominance has gone unnoticed or ignored too long, it may be irreversible or require drastic measures to avoid potential damage. Much like cancer, this and other structural flaws in a tree is not something that the layman will readily detect in early stages, but a Certified Arborist can often to catch such potential problems before they even develop. The sooner it is detected, the easier it is to remedy through subordination. Subordination of co-dominant leaders involves choosing one leader or the other to “take over” as the main trunk. Effective correction takes time, sometimes a number of years, because subordination utilizes the natural growth patterns of trees. Basically, the leader that has been chosen as dominant will be left mostly alone. The other leader will be subordinated using heavy thinning. Over time, this subordinated leader’s growth will be slowed, while the dominant leader will increase in diameter. The hoped-for end result is a healthy crotch where instead of a giant slingshot shape there is now a smaller branch growing from a larger trunk. If codominance with included bark is too severe to be corrected using subordination, other options include cabling, bracing, or removal of one of the major leaders (which would probably be drastic and leave ugly gaping holes in the look of the tree). Naturally, subordination would be preferable; thus the importance of catching problems before they are critical. If you aren’t sure, have a Certified Arborist look at the tree. This is their area of expertise and most will not charge anything for a consultation appointment.