by John Geiger
Drought stress takes its toll, even on fully mature trees; effective watering strategies are critical for ensuring their survival. Mature trees vary widely in their need for water depending on size, age, soil composition, slope and, most importantly, species. So, first take a minute to learn about the water requirements of your specific tree. Native and drought-resistant trees have adapted to conserving water and might need less attention compared to non-native counterparts. Don’t know what tree it is? There are a number of handy apps that will ID your tree (and plants) in seconds. “Seek” is one I use a lot.
How do I know if my tree needs water?
Simply observing your tree will tell you a lot about its current watering needs. If there are dead twigs at the outermost reaches, or the leaves are undersized and/or turning brown while the rest of the tree looks normal, its not getting enough water. This is one of the first signs of drought stress. You also want to probe the soil. Insert a 12″ long screwdriver, or similar probe, into the soil at the drip line of your tree (see the diagram below). If it slides in easily and soil clings to it, then it doesn’t need watering. Hard and dry means it’s time to water!
Proper tree watering practices
- Deep, Infrequent Watering: Just like with plants and lawns, it’s far better to water less often and deeply. For mature trees, once a month works well in the absence of rain. Younger trees will need more frequent watering. Deep watering encourages the roots to venture down into the soil, building resilience against drought conditions, disease, and pests. Use soaker hoses or drip irrigation systems to gradually release water to the soil over a longer period of time.
- Focus on the Drip Line: The bulk of a tree’s feeder roots resides at the drip line. Concentrate your watering efforts in this area to optimize nourishment.
- Mulch it: Mulch retains moisture, controls weeds, and maintains consistent soil temperature. Apply 2 inches thick and avoid touching the trunk – deep enough to help them retain moisture around their root zones and shallow enough to allow rainwater to pass through, without rotting the trunk.
- Time it Right: Water during the early morning or evening to minimize water loss due to evaporation, ensuring more water reaches the roots.
- Avoid Overwatering: As water permeates the soil, it will displace oxygen from the pore spaces between soil particles. Overwatering can suffocate tiny roots, so remember: a tree will tolerate drought better without excess water.
- Avoid the trunk: To prevent root rot, never apply water directly to the trunk; start at least 10 inches away from the trunk. Again, most of the active water absorption happens around the drip line.
- Harness Rainwater: If feasible, collect rainwater for tree irrigation. Rainwater is free of chemicals and naturally suited for plant nourishment.
- Vigilance and Care: Keep a watchful eye on your trees for signs of stress such as wilting leaves or premature shedding. Adjust your watering regimen as needed.
- Pruning Wisdom: Avoid pruning major branches. This can increase water needs. Trim small dead or diseased branches to reduce a tree’s overall water requirements, aiding in efficient resource allocation.
