While many Iowans enjoyed those spurts of warm weather we had during January, the temporary respites from winter may have killed some of our trees now that we’re back in the deep freeze.
Tivon Feeley, the Iowa DNR’s forest health program leader, anticipates moderate to severe winter burn damage statewide to conifers, like white pines. Feeley says the January thaws forced some trees to use the water reserves in their needles.
“So even though the ground is frozen, the ambient temperature above is warm, and the conifers are tricked, especially the non-native conifers, when they think that it’s springtime: ‘Let’s start using up the water reserves,’ but the root system is still frozen,” Feeley says, “so they can’t get more moisture up into that tree, and so they dry out, and that’s what winter desiccation is.”
The symptoms include browning or bleaching of the needles, trees losing needles, and eventually, tree death. Feeley says we may not see the full impact of the winter burn until much warmer weather sets in, like in late May or early June.
“You look at our eastern red cedar right now. They’re brown. They’re dormant. They’ve evolved in our climate. They know what to expect, and they’re going to stay brown until we get all that spring rain, and then they’ll start to green up late,” Feeley says. “Our non-native conifers are not used to that, so as soon as it’s warm, they think it’s spring, and they’ll start trying to use water up that they don’t have.”
There’s really nothing Iowa homeowners can do at this point in the year to save the trees if they’re burned, but Feeley says to remember this situation in several months when autumn returns.
“The best thing to do to prevent this is to mulch around the base of your tree, and if we’re dry in the fall, which is pretty common in Iowa, and you have non-native conifers, to water that all around them to get an ample moisture built up to carry it through these warm days,” Feeley says, “because later this week, it looks like we’re going to warm up again, so it could be another situation where we’re set up for this winter desiccation.”
If needles on the tree are dead but the buds are alive, he says new plant foliage will regrow to replace the winter-burned foliage. If both the buds and needles are dead, Feeley says the tree will not recover.