Summer drought conditions can significantly affect the lifespan of your trees if not properly maintained both during AND after the drought period. It can be difficult to remember to water trees during the summer, especially after coming out of a rainy spring season. The best, and most proactive strategy to prevent drought stress in trees is to water them regularly.
Trees need to receive 1 inch of water per week throughout the spring, summer, and fall. If the rainfall is less than that in any given week, additional watering is required to maintain adequate soil moisture. The best method for watering is a slow soak system onto the entire root zone area, either using a soaker hose or trickle from a garden hose. This approach eliminates evaporation of puddled water, which is a prominent issue due to SE Wisconsin’s dense clay soils. A slow soak also ensures the water is getting deep into the root zone. Roots can extend as far out as the drip line, or where the tree branches end, and may sometimes even extend beyond the drip line if there is enough space. The best time of day to water is either early morning or in the evening. A rain gauge is an effective method for measuring the amount of rainwater received each week.
Thanks to extensive root systems, trees are able to withstand initial drought conditions. However, prolonged drought periods can weaken trees to the point where they become targets for disease and secondary pests such as borers and disease-carrying insects. For example, non-protected American elms are more likely to succumb to Dutch Elm Disease & paper birch may have higher chance of being attacked by Bronze Birch Borers. These secondary borer infestations can occur even after the drought period has ended, while the tree is in a weakened state and still recovering.
Like all plants, turf is also affected by drought conditions and will compete with trees for water resources. If turf exists on top of the root zone, additional watering will be required to move through the turf zone and penetrate into the tree root zone. Any tree that has turf covering the root zone would benefit from removing the turf from the drip zone and replacing it with a thin layer of mulch (2-3 inches). This will reduce competition between the turf and root zone of the tree. The mulch is easily penetrable, which allows water to access the roots quicker. Mulch creates a protective layer to shield any surface roots from mower blades and ground compression. Most importantly, during the drought season mulch holds the water in the root zone, so it does not evaporate in the high heat.
The following are symptoms of drought stress to keep an eye out for: wilted leaves, smaller than normal leaves (undersized), sparse canopy, leaf scorch (browning/curling of leaf margins), yellowing of leaves, premature fall color/leaf drop. If you are concerned about your trees health contact one of our expert arborists today!
-Brittany Damschroder- Hoppe Tree Service Certified arborist, received a B.S. in Fisheries and Wildlife from Michigan State University, and has worked in the tree care industry since graduating in 2012.