By: Anthony C. Arnoldi, Board-Certified Master Arborist WI-0102B
This spring many trees were unable to produce much foliage. Many produced nothing but seeds, at first, and when these ripened, all you could see was brown. Such trees seemed more dead than alive. Later on, some foliage started to be produced, but these leaves were undersized, off-color, and left the tree much thinner than normal. On other trees, some sections never did leaf out and the remaining parts look weak.
Trees that have a treatment history for various problems, and have been stable for some time, have begun to struggle again. Dead and weak trees are everywhere.
The main reason for this is the continued and cumulative stress of year after year of rainfall shortages. Over the last ten years, rainfall has been below normal. Deep soil moisture was depleted years ago and trees are deriving water from the top two to eight inches only. When this dries up, the trees are under extreme stress again. And it does dry up, quite easily. We were behind five inches of rain for the year 2006 alone before we received the four inches of rain in May. For a while, things seemed great (and wet). However, a mere two weeks later, turf areas were again going dormant and trees resumed showing stress symptoms.
Even trees that are in fairly well-watered yards did not escape completely. Water from wells and municipal sources is even harder and more alkaline than our soil, and is therefore, not as easy for the trees to use as rainwater. Even so, supplemental watering must be done in order to save our trees.
The watering recommendation for trees has always been to water the entire area under the dripline. However, in extended drought situations, this is proving to be insufficient. Consider the configuration of a tree’s root system. It is extremely flat and shallow, spreading out to three to four times the height of the tree, in all directions! Many people do not realize this and water very limited areas of the dripline area. All of the roots, well beyond the dripline, never benefit from the watering, and if they stay dry too long, they die. This has been happening steadily and has meant more crown dieback and dead trees. We must water more widely so as to save more of the root system (see diagram).
Drought contributes major stress to the decline spiral. If a tree dies, it is usually the result of several contributing stresses acting over an extended time period. Insect attack, poor pruning or pruning neglect, soil compaction, storm damage and disease infection are some of the factors combining with drought to cause decline and eventual death. Wood-boring insects and root rot fungi are especially prevalent, taking advantage of weakened trees.
The way to recovery must utilize proper watering methods (also see Drought Countermeasures article from our summer 2005 newsletter). It must also include efforts to restore lost feeder roots. Root biostimulants, mycorrhizal root inoculations and specialized fertilizations provide this help. Don’t let your trees feel the full effects of this damage. Call us so we can show you what the best program is.
© Copyright 2006 – Wachtel Tree Science & Service, Inc.