Hand watering, soaker hoses, and drip irrigation are more efficient than sprinklers and overhead irrigation, but all methods can work. Another method of monitoring watering needs is to use a biological indicator plant such as impatiens, ajuga, or coleus. These indicator plants, which can be planted in the root zone of the tree of interest, wilt dramatically when water becomes limiting. When the indicator plants stay wilted for more than an hour after they are in the shade, the tree and the indicator plants should be watered. Repeat the watering when the indicator plants again wilt.
Indicator plants adjust for climatic conditions such as natural rainfall, temperature, and wind.