Do trees need water in winter in the high desert?

Winter here is often cold, sunny and windy, not snowy, and dry spells pull moisture out of the soil. This post summarizes the Extension guide and adds what we can say as a tree crew.

Why would a tree need water in winter?

Extension says winter here does not always bring the deep snowpack trees rely on in other regions. Instead there can be long stretches of cold, sunny, windy weather that dries the soil. Evergreens keep needles through winter and continue to photosynthesize at a low level, so they keep using water. Dormant deciduous trees still have active roots. Stress usually shows in late winter or early spring, after the damage is done.

The climate is dry to begin with. NOAA's 1991 to 2020 normals put yearly precipitation at 9.34 inches in Carson City and 7.35 at the Reno airport.

How often and when should you water?

Extension's guide recommends watering about once every 3 to 4 weeks in winter, when daytime temperatures are above 40 degrees F and the soil is free of snow and ice, so water can soak in. Light snow adds little usable moisture, so you still need to water unless there is a significant, lasting snowpack. For newly planted evergreens, the guide says every 2 to 3 weeks for the first 2 to 3 years, with more frequent soil checks.

How do you water a tree in winter?

Use a slow trickle from a hose or a soaker hose, and soak the soil 12 to 18 inches deep, where most roots are. Water under the outer edge of the branches (the dripline), not at the trunk. Extension also recommends 2 to 4 inches of mulch, kept a few inches from the trunk.

Do not overwater. Let the soil dry between waterings and remove standing water by nightfall to avoid freeze damage to the trunk. Check the soil with a probe or long screwdriver: it pushes easily into wet soil and stops where the soil is dry.

Which trees need it most?

The guide covers all trees, evergreen and deciduous, and singles out evergreens because they hold their needles. Trees on slopes, in wind and in rock or gravel landscaping may dry out faster. If you converted lawn to rock, check what your trees now get. See watering mature trees in the high desert.

What about a tree that already looks stressed?

Browning, thin crowns and dead tips can come from water, roots, structure or pests, and watering alone will not tell you which. A certified arborist can say whether the answer is pruning, support or removal. See drought stress and dieback. Battle Born does not fertilize, spray or treat for pests. Battle Born Tree Service has two ISA Certified Arborists on staff, including ISA Certified Arborist WE-11728A; see arborist consultation. Call 775.232.8243 for a free estimate.

Keep a note on the calendar for the first mild day of each month. If the ground is thawed and there is no snow on it, that is your watering window. Hoses left connected can freeze and split, so drain them after each use. Moving the trickle around the canopy edge in a different spot each time covers more of the root zone than soaking one place.