Water-Wise Strategies for Arborists Sustainable Irrigation and Tree Health By Sandy John
As climate change alters weather pat- terns, resulting in drier, hotter condi- tions, tree care professionals face twin dilemmas: trees suffering from reduced rainfall and local restrictions on water usage for irrigation. To overcome both challenges, arborists need to adopt sustainable practices to conserve water while maintaining plant health. Trees are integral to the natural water cycle, and a loss of tree cover can result in more soil evaporation, exacerbating drought conditions. A healthy tree canopy absorbs storm- water, reducing the number of pollut- ants washed into streams and rivers. Meanwhile, the leaves of the canopy also slow down how quickly rain reach- es the forest floor, allowing the ground more time to absorb water. For example, a USDA Forest Service study found that a 54% tree cover in a Pennsylvania watershed reduced stormwater runoff by 11%.
Even when rainfall is abundant, prac- ticing water conservation offers several benefits. Using less water — whether from municipal sources or pumped from onsite ponds — lowers costs for busi- nesses or clients, as they pay less for water or diesel fuel to operate pumps. Additionally, delivering the correct amount of water deeply into the soil ensures that trees are healthier and better equipped to withstand drought . Water conservation practices such as monitoring soil moisture, understand- ing the water needs of different spe- cies, and applying mulch correctly all contribute to maintaining tree health. SUSTAINABLE WATER PRACTICES When designing a landscape from scratch, prioritizing sustainable water practices is key. Planting native trees that are acclimated to local rainfall pat- terns reduces the need for irrigation. Grouping trees and plants with simi- lar water needs further minimizes the risk of over- or under-watering. In areas
exposed to intense sun or high winds that dry out soil, finding ways to mit- igate these conditions or deciding not to plant trees in such locations may be necessary. For existing tree plantings, several techniques and tools can help arborists conserve water. For instance, the New Mexico State University Extension suggests that drip irrigation can save up to 70% of applied water compared to traditional sprinkler systems. Zachary Hall, general manager of Mil- lican Nurseries LLC in Chichester, NH, is a proponent of drip irrigation. He for- merly served as the irrigation supervi- sor for the wholesale nursery and was responsible for irrigation for 16 years. “When I first started, 75% of our material was watered with overhead sprinklers,” he said. Now, about three-quarters of the nurs- ery is equipped with driplines with emitters going to tree root balls.
48 | ArborTIMES Fall 2024
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