Maintain vigor through proper watering and fertilizing. Water deeply to encourage deep root systems that enable trees to withstand environmental stress such as drouth and winter desiccation. Sufficient moisture will help keep the trees vigorous enough to withstand pest attacks, as well as help prevent winter injury. Avoid frequent, light waterings, and watering only at the base of the tree trunk. Trees suffering from drought can be selectively pruned to reduce transpiration, which is the loss of water due to evaporation through the leaves.
Drought occurs when transpiration exceeds the plant's ability to supply water through the roots.
Prior to planting, reduce foliage of transplants by pruning to minimize early injury due to water stress. To determine if trees need fertilizing, have the soil tested and supply any missing nutrients. Avoid overfertilization, which can also harm trees and ornamentals. In many parts of Montana, additional tree fertilizers are not needed, especially when planted in turf areas that receive fertilizers. Unless trees are showing symptoms of nutrient deficience, such as chlorosis, stunted growth, or deformed foliage, refrain from fertilizing them unless soil tests indicate otherwise.