With the continuing dry weather we are experiencing this season, many types of plants and trees are being negatively affected.
The last few years, our trees had been stressed because of excessive moisture. Now they are being stressed because of lack of moisture. On a normal dry year, it wouldn’t be such a big deal, but trees in this area were damaged by high water tables and water-logged soil. Their root systems were diminished due to the lack of oxygen in the soil.
These same trees were bound to show signs of stress this season, but now these signs are being exacerbated by extreme drought and additional root loss. It is not hard to find trees that are expressing drought injury symptoms, such as yellowing and wilting leaves, twig and branch dieback, yellowing evergreen needles and even death. Colorado blue spruce is native to a region that receives between 18-24 inches of annual precipitation, so not too surprisingly, this tree is worse off than many of our native trees, such as bur oak and Eastern red cedar.
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Many pests have developed means of exploiting the dehydrated condition of trees, and some can detect these trees by the yellowish color of the foliage or higher plant temperature.
There are a number of practices homeowners can do to ease the problems on their yard trees. First, water your trees, especially the ones planted within the last two years. Until the ground freezes, give them a slow soaking about once a week of 5-10 gallons for each inch of trunk diameter, which is measured 4.5 feet above the ground. This means a 5-inch diameter tree should receive about 25 to 50 gallons of water at least once a week. New residential areas or other areas with poor soil quality should monitor more closely so the soils don’t become waterlogged, especially if an irrigation system is being used.
In addition to watering, the area beneath the tree should be mulched to a depth of 2-3 inches with shredded bark mulch. The mulch should not be pushed up against the trunk of the tree. Even mature trees will benefit from the mulch circle, though their roots extend much further out.
Avoid applying fertilizers on or around trees suffering from drought. The additional salts from fertilizers might become another stress on the tree. While they might be able to tolerate this when they are healthy, trees already stressed by drought can be killed by the addition of any further stresses.
Contact me for additional information or questions at forestry@ aberdeen.sd.us or 605-26-7015.
Aaron Kiesz is the forester for the city of Aberdeen Parks, Recreation and Forestry Department. His column runs occasionally.