Should You Water Trees in Winter? Experts Weigh In

By winter, most plants in the garden have gone to sleep for the season. But certain trees are still putting on a show with their beautiful evergreen foliage, raising the question of whether winter watering is necessary. While the watering needs of trees are largely weather-dependent, there are instances when supplemental irrigation is beneficial. To keep your plants healthy during the coldest months of the year, we consulted gardening experts who shared their tips for when (and when not to) water trees in winter.

Do You Need to Water Trees in Winter?

Although most trees are dormant during winter, they can still lose water from their tissue. "Broadleaved evergreens and coniferous evergreens (pines, spruces, arborvitaes, junipers, etc.) can transpire small amounts of water from their leaves, especially on days when it might be relatively warm and sunny," says Andrew Bunting, vice president of horticulture at the Pennsylvania Horticultural Society.

If fall and winter precipitation are low, tree health can suffer, leading to poor growth, dieback, and increased susceptibility to pests and disease, says Ankit Singh, assistant professor and ornamental horticulture educator at the University of Maine Extension. While normal autumns with ample rainfall are typically enough to get trees through winter, supplemental irrigation may be necessary during periods of drought, especially for newly planted trees.

How Often to Water Deciduous Trees in Winter

Deciduous trees typically need the least water in winter because they drop their leaves and are not actively transpiring. "In most years, natural precipitation is enough," says Singh. "However, during a dry winter or drought, a deep watering once every four to six weeks (if the ground isn't frozen) can be helpful, particularly for young or recently planted trees."

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How Often to Water Evergreens in Winter

Evergreen trees need moist soil, as they continue to lose water from their leaves even when it's cold outside. Sometimes normal precipitation is enough, but during periods of drought, supplemental irrigation may be required.

Conifers

Coniferous evergreens need more water than deciduous trees in winter because the foliage continues to transpire during the cold months, says Damon Abdi, assistant professor of landscape horticulture at Louisiana State University AgCenter. Inadequate moisture can lead to desiccation of the leaves, possible dieback, and, in extreme situations, death, Bunting warns. Aim to water coniferous evergreens about once a month during winter when temperatures are above freezing, and the soil is not frozen.

Broadleaf

Broadleaf evergreens, such as holly, rhododendron, and boxwood, are the most susceptible to winter moisture stress and typically require a little more water than coniferous evergreens. "Their leaves continue to transpire, and they can suffer from winter burn if roots cannot replace lost water," says Singh. "In dry winters, these trees and shrubs may need watering every three to four weeks, only when the ground is unfrozen."

When to Water in Winter

The best time to water trees during winter is when temperatures are at least 40 degrees Fahrenheit and the ground isn't frozen solid, so the water can thoroughly soak into the soil, says Abdi. Late morning to early afternoon is ideal ad this gives the water time to soak in before nighttime temperatures set in, Singh says, adding that you should avoid watering when a hard freeze is expected immediately afterward.

Common Mistakes to Avoid

Trees are susceptible to over- and underwatering, so make sure to avoid these common pitfalls when making sure your plants are hydrated during winter.

• Only watering close to the stem: The roots of established trees spread, extending beyond the drip line. Watering around the trunk may not reach the far-reaching roots, Abdi says.
• Watering when the ground is frozen: Winter watering should only occur when the ground thaws. Watering when the soil is frozen prevents it from reaching the roots, Singh says.
• Overwatering: Overwatering can be just as damaging as underwatering, leading to root damage or poor soil aeration.