Since trees are living organisms they need water to live and grow. Trees cannot move to areas of water during droughts, so they must adapt. Like most plants an inch of rainfall per week is optimum for growth. Water stressed trees will show various symptoms such as yellowing, leaf browning and even defoliation. Newly planted trees especially need water as they are re-growing the root system lost to transplanting. These plants are relatively easy to water due to their small size. Drip irrigation systems work best as water is slowly soaked into the soil. Mature trees present a challenge for watering due to the large amount of water needed. This could be several hundred gallons per week. When selecting plantings for dry sites use drought tolerant species. These include White Oaks, Hickory, Honeylocust, and hybrid Elms. Remember however that all newly planted species need water whether drought tolerant or not.