We winterize things to prepare them for the extremes of winter weather. Have you considered winterizing your landscape trees (especially newly planted trees)? A Purdue Extension expert authored a publication on this subject, from which we’ll glean some important tips.
“As trees in our urban and suburban landscapes prepare for winter dormancy and cold, they could use a little extra care from you to ensure a good start in the spring,” said Lindsey Purcell, Purdue Extension urban forestry specialist (retired).
“Winter conditions will make finding moisture a challenge – and keeping plant cells hydrated in winter is critical for survival,” said Purcell. “Summer and fall drought conditions can place trees in an overall water deficit, predisposing them to pest issues and poor health the next growing season.” He said that young or newly planted trees will require more attention because of their limited ability to obtain water in their growing environment.
This is timely advice, as the latest check of the U.S. Drought Monitor (https://droughtmonitor.unl.edu/) places northeast Indiana in a moderate to severe drought. The turfgrass in your lawn is probably telling you the same story.
“The key to survival is giving trees adequate moisture before winter freezes the world around them,” said Purcell.
“Whenever rainfall is insufficient for extended periods, supplemental water is needed, especially on newly planted and less-established trees,” said Purcell. “Follow the ‘5 + 5 rule,’ which says to provide 5 gallons of water plus another 5 gallons of water for every diameter-inch of tree trunk.” He said for mature and well-established trees, 1 inch of supplemental water applied to the root zone every week should keep soil moisture at adequate levels.
Purcell offered additional winterizing tips.
Trunk wrapping: “Smooth or thin-bark trees like honey locust, crabapples, linden, and especially maple, are susceptible to sunscald and frost cracks because of the temperature fluctuations from sun exposure in the winter,” said Purcell. “The wounds caused by temperature fluctuations can leave the tree exposed to fungal organisms, which cause decay in the tree.” He said prevention includes guarding the trunks of younger and smooth-bark trees up to about the first branches using a flexible, white tree wrap. It should be removed in spring after the last freezing temperatures.
Mulching: “Mulch benefits trees all year long, not just during the summer months,” said Purcell. “Refresh the mulch layer placed in the spring so that there are about 2-3 inches of chips, bark, or other organic mulch over the root zone of the tree.” Start from the base of the tree (with NO mulch against the trunk – maintain an air gap) out to roughly the drip line (ends) of branches. Mulching reduces evaporation and insulates roots against winter temperatures. A mulch ring also offers a visual cue to mowers to stay away from the base of the tree and not injure it with the mower deck. Don’t go overboard, though – do not mound mulch against the truck like a volcano. For previously mulched trees, Purcell urged homeowners to rough up the mulch around trees. “During the course of the summer, it can weave so tightly that it becomes hydrophobic and water actually runs off the root zone,” he said.
Pruning: Do only what may appear necessary now. For the bulk of ornamental tree pruning, wait for late winter or early spring or during the next growing season. “Prune trees to remove dying, diseased, or dead branches, or to improve branching structure,” said Purcell. “This is also a good time to remove water sprouts and basal sprouts.” Purcell cautioned that green wood pruning as we enter winter should be limited.
Fertilizing: “If trees are not stressed from moisture deficits, apply a complete fertilizer with micronutrients,” said Purcell. “Use a low-nitrogen formulation to prevent a late flush of new growth.” The proper timing of fall fertilization is generally right after leaf drop. However, with our current soil water shortage, it’s probably best to skip this step, at least for now.
For more information, find Purcell’s publication, entitled, “Winterize Your Trees,” at www.edustore.purdue.edu.