Trees must be properly cared for during winter

Winter begins Dec. 21, which means it’s time to batten down the hatches. Homeowners should clear gutters of any debris, make sure their heating system is in top working order, and stock food and other supplies in the event of a power outage.

But what about those trees in the yard? They may look hardy enough to weather the chilly three-month season, but trees, like any living thing, must receive the proper care to survive and thrive into the spring and beyond.

Brian Humphrey, owner of Gilroy-based Pleasant Valley Tree Care, is quick to pass on winter tips for tree caregivers. Humphrey, who was born and raised in Gilroy, is an International Society of Arboriculture-certified arborist who began working in the horticulture field in 1996, apprenticing under four certified arborists in Santa Cruz.

The company provides a variety of tree-related services, including consultation, selection, planting, pruning, removal, disease diagnosis and more.

The following are some of Humphrey’s recommendations for the winter season, along with some tips from other sources.


“Winter is the dormant time for many trees, and it is believed by many people to be the best time of year to trim,” Humphrey said.

Winter is the perfect time to prune conifers (pines, cedars, firs and spruce), he said. During this season, the trees have less sap flowing, making it less likely to drip.

Monterey pines, which are highly sensitive to disease, are more tolerant of pruning in the winter months. But only prune if necessary, Humphrey advised.

Why is it important to prune trees in the first place? According to the “Care of Trees” website, pruning is not only for aesthetic value but for practical reasons, as it reduces the chance for heavy limbs to come crashing down during winter storms and causing major damage, and can also halt diseases that could spread rapidly during the warmer months.

Branches ripe for pruning are those that are dead, dying, damaged or diseased.

Frost-sensitive trees and plants, however, should be pruned after winter has passed, according to Humphrey. These include citrus, jacaranda, oleander and other tropical plants.


Trees, like people, need to find some sort of warm comfort during winter.

Lights that emit heat can provide warmth while also protecting against frost, Humphrey recommended. And those festive lights during the holiday season can also serve a more practical purpose: Christmas lights, if they generate heat, can be wrapped around trees as a way to provide warmth.

With the nights dropping to freezing temperatures, frost-sensitive trees and plants should be covered overnight if temperatures are expected to be 32 degrees or lower, according to Humphrey.

“You can use an old sheet, a tarp or clear plastic,” he said. “I suggest using something that lets light in so that you do not have to take off and re-cover every day.”

Tree care website also recommends that potted trees be moved to more protective areas, such as an outdoor hallway or other covered area.

Mulch is another way to provide warmth. According to, soil should be covered with a three- to five-inch layer of mulch (using organic matter such as wood chips) starting a few inches away from the base of the trunk to two or more feet from the tree in all directions.


It may seem counterintuitive to water trees during winter when there is so much rain, but it is necessary for their survival like in any other season.

Humphrey recommends watering trees and plants before a hard freeze. It is always a good idea to water newly planted trees before a freeze as well, he added. also advises watering as a way to retain heat. According to the website, moist soil absorbs more solar radiation than dry soil, which re-radiates heat during the night.

“If you have a large tree that needs protection, running sprinklers at the coldest time of the day (usually between 4am and 6am) can give it a slight edge,” the website states. “The strategy makes use of latent heat released when water changes from liquid to a solid. When ice crystals form on the leaf surface, they draw moisture from the leaf tissue. The damage from this dehydration will be less severe if the plant is not already drought-stressed.”

Young trees should be watered every one to two weeks, while mature trees should receive water once a month or every other month.

Assessing frost damage

Frost damage is still a possibility, even if one has taken all the suggested measures in preventing it.

Humphrey said residents should wait to remove any damage from trees and plants until after winter ends.

“Frost damage can still provide protection to trees and plants even though it is dead,” he said. states that new growth may still sprout out of branches that were initially thought were dead. Tree caregivers are advised to wait and see what (if anything) sprouts in the spring.

“If dieback is severe enough and your tree has lost ‘shade,’ protect the now-unshaded portions of the trunk/branches from the sun, with a physical cover or with whitewash (1:1 ratio of latex paint and water),” the website recommends.

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