During autumn and winter, we often experience dry air, little precipitation, and wide daily temperature fluctuations. This is made worse when the weather is drier and colder than normal. Trees, shrubs, and turf may be damaged if not given supplemental irrigation. As a rule of thumb, evergreen plants need more supplemental water during winter than do deciduous ones.
Long, dry fall and winter periods can result in death or injury to plant root systems. Affected plants may appear perfectly normal and resume growth in the spring utilizing stored energy reserves, only to weaken and die in late spring or early summer when the stored energy runs out. Weakened plants are also more susceptible to insect and disease problems.
Plants take water into their roots from the soil through osmosis: the concentration of dissolved materials is greater inside the plant root than in the soil causing water to move into the plant. Once inside the plant, water is pulled by capillary action up the stem and to the leaves before the excess is released to the atmosphere. In general, the plants use about 10% of this water for photosynthesis, cellular metabolism and cell growth. The remaining 90% is simply passed through during the process which is called transpiration.
Recently planted trees and shrubs are especially susceptible to damage from lack of adequate soil moisture. Once a healthy root system has been reestablished, plants have increased tolerance to drought, but few evergreen landscape plants can endure extended drought periods. Even drought-tolerant plants will benefit from infrequent irrigation during dry winter months.
Apply irrigation early in the day so it can soak in before possible freezing occurs during the night. For established landscape trees and shrubs, four to six weeks should be the maximum amount of time between irrigations. Of course this varies with soil texture and species.
I encourage everyone to monitor precipitation, soil moisture and irrigation systems in the winter to maintain evergreens during dry winter periods. We should all seek a balance between our landscapes and the quantity of irrigation water required to support them. Well-placed evergreen trees can offer privacy and wind protection, but too many trees can be overly consumptive of our precious water resources.
Jeff Schalau, Associate Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County
The Garden Rhapsody is just such a wonderful system to use for irrigation all year round. It is very cost effective. Please re-use your grey water.