As spring leaves bring a brilliant green to Southeastern Minnesota, many readers are noticing evergreen trees and bushes are suddenly turning brown, appearing to be dying. Jim Edgar of Minnesota Department of Natural Resources (DNR) Forestry is getting calls from area residents about their concerns seeking advice about the best care for these evergreens.
Reports of the problem in Fillmore County coincided with reports from other counties, so the MN DNR, located in St. Paul, sent out a message stating, “The forest health team has recently received reports of a handful of spruce, white cedar (arborvitae), and white pine that appeared to die suddenly in Fillmore County, Freeborn County, Chisago County (near Taylors Falls), Goodhue County, and Houston County. In the most extreme cases, spruce shed needles in the upper 90% of the canopy within a few days, while the bottom branches remained green.”
Edgar comments, “What is actually happening is that evergreens are showing the effect of hot, windy, and dry conditions during the weekend of April 28-30 when the ground was still frozen and tree roots were unable to replace moisture lost through foliage.”
People are asking Edgar an array of questions. He says, “Homeowners in multiple counties are noticing some of their evergreen trees, often in windbreaks, suddenly turning brown. In most cases, the trees looked healthy through the winter with symptoms showing only in the past couple of weeks.”
This type of damage to conifers is often referred to as “winter burn.” “Winter burn is a common problem of evergreens,” mentions Laura Jull, UW-Madison Horticulture. Her article from the University of Wisconsin Extension Office describes this process. “Foliage starts to brown at the tips of branches with browning progressing inward toward the center of the plant. On broad-leaved evergreens, leaf edges typically brown first, followed by browning of entire leaves. Foliage facing south, southwest or west is most often affected.”
So what are those noticing winter burn to do? It seems as with many concerns with nature, observation is vitally important. “Similar symptoms on multiple tree species at the same time usually indicate an environmental problem instead of an insect or disease cause,” remarks Edgar. “The lingering winter, with late snow and frost still in the ground, kept the roots of many trees dormant well into late April. The red flag fire conditions (hot, dry, and very windy) that occurred just a week-and-a-half after our last (hopefully) snow of the spring caused the foliage of some coniferous trees to lose moisture and dry out. It appears that the roots were not able to replace water lost through the needles or not replace water fast enough and needles, buds, and small-diameter twigs dried out and died.”
All trees in a planting or windbreak may not be affected. Edgar says, “There are likely multiple reasons for this, including: warmer soil around some trees allowed roots to function and replace lost water from foliage, some trees were shielded from the wind, and genetic variation of trees affected some trees more than others.”
Questions remain as people wonder how soon they need to wait to know if a shrub or tree is dying. “By mid-June, if a branch or tree that is not greening up or showing green buds it is likely dead.” comments Edgar. “Break off branches, beginning at the tip, progressing back toward the main stem. Branches that are brittle and brown are dead. If the branch is pliable and green it may still be able to produce buds. Break off buds; coniferous buds are usually resinous and have a fresh smell. If the buds are dry and brown they are dead and will not produce new growth.”
In her article on winter burn, Jull offers some pruning tips. “Pines, spruces and firs typically produce new growth at branch tips in spring that will replace winter burn-damaged needles, and thus pruning may not be required on these evergreens. After a couple of growing seasons, new foliage will fill in the areas that were damaged. If an entire evergreen is brown, recovery is unlikely and the plant should be replaced with something (e.g., a deciduous shrub or tree) that is better-suited to the site.”
Edgar recommends replacing the dead trees if they are an important part of a windbreak or yard planting. However, he advises, “It may be best to wait until fall or next spring to re-plant, as mid-summer is a tough time to put a new tree seedling in the ground and expect it to survive.”
So the bottom line according to the DNR is to, “Wait and see how your tree does this spring. If it still has 50% or more of the canopy, it may recover.” Know that Jim Edgar and the staff of the Minnesota Department of Natural Resources are available to help, so visit their website www.dnr.state.mn.us.
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