(Riverton, WY) A significant number of evergreen trees in Fremont County are turning brown, causing many residents to wonder if the trees are dying due to the long, harsh winter.
SAF/ISA certified forester and arborist Josh Shroyer said a few things may be contributing to pine and spruce needles turning brown. “Each, individually, can cause this browning of needles,” he said, “but in most cases, it is really a combination of multiple factors. I am thinking that is what most folks are seeing.”
Lack of irrigation
According to Shroyer, pine and spruce “are not really supposed to grow here. They only do as well as they do due to constant, annual irrigation. Therefore, a lack of irrigation, even for a while in the summer, can predispose certain trees to stress.”
“Now, look at the winter we have had,” Shroyer continued. “We have been below freezing for a long time this year, and have hit -30 degrees or colder a number of times. Even though we have had snow cover, the ground has been frozen, and therefore a limited amount of available moisture for tree roots to take up. So dry and frozen conditions, along with cold, are showing typical ‘winter injury’ on a lot of these trees, especially spruce.”
Shroyer said that because of the extended winter and excessive amounts of snow, many have been using more de-icing salts than usual.
“These can accumulate in certain areas as we have been warming up and the overall snowpack melting around the county,” he said. “I have seen a few trees showing signs of salt toxicity. Again, this will turn needles brown or purple, or have a ‘washed out’ appearance.”
Another problem that has recently turned some needles brown has been due to warmer days and a higher sun angle on parts of trees and branches that may have been covered by snow drifts.
“As the snow has melted down, these branches that have been somewhat protected are all of a sudden exposed to the bright sunlight, as well as light reflected from the snow,” Shroyer said. “These needles have to deal with the intense light and therefore warmth…only to have some of our nighttime lows back below zero.”
Jim Brodle, who recently retired after 15 years on the Riverton Tree Board, said that in his experience, most pine trees will come out of it after the winter. They have a Norway Spruce and Limber, Bristlecone, Mugo, Lodgepole pines, and an Austrian pine tree on their property.
“My Austrian pine is bad,” he said. “I have Bristlecone pine…the kind that lasts for thousands of years, and it’s stressed. But I’ve seen it stressed before, so I think it’ll be okay. My Limber pine is probably okay.”
Brodle also mentioned the “sun scald,” with the sun shining off the snow and the heat stressing the tree. “The Austrian pine is a good-sized tree,” he said, “When we planted that tree new, it grew nicely in the summertime, and it went through the winter. I think it was after the first winter when the south half of the tree was basically dead and the north side wasn’t. It’s shaded by other trees, so it is probably a combination of issues, but a temperature-type thing more than anything else.”
“We won’t know until we wait and see if there’s new growth,” said Jim’s wife, Carol, both Master Gardeners. “If there’s new growth and it’s all healthy, then all this other stuff doesn’t really matter.”
Shroyer currently serves on the Riverton Tree Board, and is the owner of Flaming Trees Solutions, LLC.
“The good news is, most of these affected trees should come out and survive,” Shroyer added. “Homeowners need to be sure to provide adequate watering once the ground thaws out. Supplemental fertilizer is generally not needed but could be helpful in certain situations. Also, with the trees already stressed, be sure to avoid yard supplements such as a ‘weed and feed’ as these actually stress the trees even more.”
Regarding insect or disease issues, Shroyer said those problems typically don’t show up at this time of year.
“You will see these issues develop in the summer months,” he said. “Having a tree expert perform a detailed diagnosis is the best bet for your long-term tree health.”