Written by: Certified Master Arborist, Tony Arnoldi
Imagine a car driving along at 40 miles per hour. Suddenly, the car is put into reverse! What follows is a terrible disaster – it was an impossible maneuver! This is analogous to what is happening to our trees. They were struggling along for the last 6 years in constant rains, keeping the soil nearly continuously too wet. Roots were drowning from lack of oxygen and root rot fungi were taking advantage of this and attacking more and more roots.
This was hard enough, but now we have the exact opposite! As of this writing, we had reached a deficit in rainfall of 7.5 inches. This is a huge amount and if anyone remembers the heat and drought of 1988 – this is feeling uncomfortably similar. Already lawns are burning up; the area rivers are very shallow; trees, shrubs and perennials are displaying wilted or shedding leaves; and the ground is starting to crack open as shrinkage from drying increases.
One might think: no problem – a too wet period followed by a too dry period should cancel out each other and end up with a decent or at least a tolerable situation. This is definitely not the case – these two stressful periods add together for an even more stressful result. The result is greater (worse) than the sum of the 2 parts. Trees that were functioning with diminished root systems because of the losses from drowning plus the attack from root rot fungi, now have to extract water from increasingly dry soil – very hard to do. Also consider that the soil moisture that we did have at the beginning of the spring, (thanks mostly to a good snowpack), enabled a good growth surge this spring – long shoots with many leaves. But now, all this growth needs adequate moisture to sustain it. Already trees have begun to drop some leaves as a strategy to conserve precious and limited water. Early fall color is staring to show on scattered leaves of Serviceberries, Autumn Blaze maples, Crabapples, and other trees. This is a stress reaction – the trees are “talking.” What they are saying is “I am stressed – water me and hurry.”
So, what can be done? Providing water is certainly the first and main step. Recognizing the relative drought tolerance of your different trees can help you triage the list and provide the first and most frequent waterings to the most vulnerable species. Recognizing the driest sites on your property can help prioritize also. Measures to conserve water that is received both from rain and the sprinkler are important. These include watering in the evening to reduce losses from evaporation, and mulching trees [creating mulch circles or adding mulch (to the proper thickness/depth) in existing beds] will help a lot.
In fall, measures to help trees replace or build the number of feeder roots will compensate for this stress and damage. These measures include Fall Fertilization with Root Biostimulants, Root Biostimulants with Systemic Fungicide, Compost Tea, and Mycorrhizal root Inoculation – all have their place. Helping in a greater capacity could utilize our Root Enhancement Service that can convert an area of root-hostile turf environment into an oasis for root growth and function.
Call your Wachtel Tree Science Certified Arborist for an assessment of the tree and site conditions and determine the best strategy for your landscape.