Most of us don’t think about the fact that trees need water during the winter. They drop their leaves and go into an apparent dormant state, so we tend to forget about them. What we don’t realize is that beneath the ground there is still plenty of activity going on. The roots continue to grow throughout the winter and need adequate water to survive.
There are few outward signs of drought stress on deciduous trees during the winter. During months when they have leaves, drought is noticeable because of leaf yellowing, wilting, curling at edges, brown tips, and dropping leaves. During the winter though, there are no leaves to act as drought indicators. Evergreens on the other hand, may turn yellow, red or purple. They also may turn brown at the tips of the needles and the browning may progress through the needle towards the twig.
Often times, drought stress may not kill a tree outright but it will set it up for more serious secondary disease and insect infestations in following years. To insure a good growing season, care must be taken to supplement the water needs of the trees throughout the year.
Trees should be watered to a depth of about twelve inches below the soil surface. The soil should be saturated within the drip line which is the area out to the outer edges of the trees branches. This will ensure that water is dispersed to all of the roots. On evergreens, water should be distributed 3 to 5 feet beyond the drip line on all sides of the tree.
Trees should be watered slowly to make certain that it penetrates to an adequate depth. Watering quickly often does not allow for penetration to sufficient depth. Shallow watering means a shallow root system. Trees will be better drought tolerant and resist wind better with a deep root system.
It is not recommended that you dig holes near the tree in order to get deeper water penetration. The holes allow more air to reach the roots and thus dry the soil more quickly. Use a soil needle or deep root feeder to apply water at a depth. Overhead spraying of trees is an inefficient way to apply water. Watering at ground level is a much more efficient application method.
As a general rule of thumb, trees need approximately 10 gallons of water per inch of trunk diameter for each watering. They will need this much water 3 – 4 times per month during April through September and 1 – 2 times per month from October through March. Newly planted trees may need even more water. Soil types and conditions as well as temperature and humidity affect the requirements.
Different species of trees have different water requirements. Drought hardy trees require much less water than species that are native to areas with high rainfall. Consult a qualified nurseryman or your local soil and water conservationist for guidelines on specific trees. The National Arbor Day Foundation also is an excellent resource for guidelines on tree care and management.
Use of mulch is recommended as a water conservation tool for trees. Wood chips, shredded bark, leaves, or evergreen needles make good mulch. They should be piled to a depth of about four inches. Mulch should be pulled away from the tree trunk for a distance of about 6 inches.
Do not fertilize trees during times when they are drought stressed. Fertilizers contain salts that may burn the roots of your trees if there is inadequate water to dilute it. The damage from the fertilizer may actually slow the trees growth rather than stimulate it as expected. Only fertilize during periods when adequate water is available.
Winter is a great time to get your trees off to a healthy start for the next year’s growing season. Adequate water is the foundation of that healthy start.