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Originally Published in September 2007.
September has given Memphis and the mid south a much needed break from record setting August temperatures and drought. It is a certainty every summer that we will have some level of drought and extreme heat which will require supplemental watering to our urban and landscape trees.
A tree’s first damage from drought occurs beneath the soil line in the form of root damage, long before any outward signs of trouble. After a tree’s unsuccessful attempts to conserve water by closing stomates(any of various small apertures, especially one of the minute orifices or slits in the epidermis of leaves, stems, etc., through which gases are exchanged), feeder roots die back, sometimes so drastically that the tree is unable to take up enough water to support itself.
In the worst case, a healthy looking tree collapses without much warning. The past 6-8 weeks we have seen an increase in apparently healthy limbs breaking in trees due to weakening in wood fibers. More often the signs of stress are much less dramatic. Overall radial growth slows; leaves are undersized and may wilt, yellow, curl or crinkle, will be marginally scorched or even turn brown and fall. Emergent shoots are short. In an effort to right the imbalance caused by root-loss, crown dieback or general thinning of the canopy occurs.
Boring insects are thought to be drawn by the odors and acoustic signals of stressed trees. The sound of water columns breaking cues the borer to invade the tree and lay eggs. The key is taking preventative action by applying treatment by spray or injection to protect prized or important trees. By the time we realize the tree is stressed, it has been heavily riddled and girdled and maybe too late. Another danger to drought stressed trees is fungus, which makes initial contact with surface roots cutting off the water supply to the tree.
While all trees are at risk during drought, some are more prone to its effects. I have personally noticed an increase in acute death to Elm tree in the mid town area. As always trees which have undergone construction damage are susceptible to drought due to an already damaged root system. New transplants are highly vulnerable to drought stress, and supplemental watering for the first few years of establishment is necessary. Even mature trees are suffering. Watering trees deeply with soaker hoses or irrigation systems-as opposed to brief, surface watering-helps sustain trees. Drought exacerbates matters for trees already under stress, like those on dry slopes, surrounded by pavement, or improperly planted. In landscape situations, consider taking action, such as moving smaller trees to a better location, alleviating compaction, or replacing moisture-draining lawn with a layer of mulch. Pine needles or a 2 to 3 inch layer of compost will also help trees in maintaining moisture. Remember to only transplant trees in the spring or fall.
The aftereffects of the current drought will likely ripple for the next 3 to 5 years, with the strongest trees surviving. Trees have developed their own mechanisms for coping with these cycles, but some trees are on the brink of survival and could go either way. If it means the difference between keeping a tree around for your lifetime or losing it in the next five years, it is worth doing something about it.
If you would like some professional help in creating a safer, more drought resistant landscape, please contact our staff for a consultation with a certified arborist today! We can help you create a plant health care plan including proper watering, pruning and pest prevention.
Please email email@example.com or call us at (901) 309-6779 for any of your tree servicing needs.