State could face ‘epic tree loss’ after storm leaves ‘zombies’
Zombies are in your yard, in parks and along roadsides and other green spaces throughout Texas.
They’re trees that are partly dead and partly alive, struggling to move forward and waiting for the next big thing — even hotter temperatures, a drought, a hurricane — to seal their fate.
Count zombie trees as one more lingering effect of February’s winter storm
Arborists and other tree experts say that in the months to come, the state could lose thousands if not millions of trees ranging from tall Mexican and California fan palms to a wide range of hardwoods such as lace bark elm, Chinese tallow and water oak. This would be the most dangerous threat to Texas’s tree inventory since the 2011 drought.
Trees with lots of dead branches and new green sprouts shooting out of the center are likely zombie trees. Even tall palms with new green fronds on top could be zombies, because you can’t see the potential damage inside of their lanky trunks.
Matt Petty, assistant district manager and a certified arborist at the Davey Tree Expert Co., said the International Society of Arboriculture is calling for a two-year watch on trees damaged in the freeze.
“The zombie tree concept comes from trees that, from a distance, appear to be normal or healthy and as you get closer, you see the differences. They’re dead and we don’t know it yet,”
Petty said, noting that the trees could have been struggling before the freeze. “Trees that lost their leaves from the freeze have sprouted out and, in many cases, look like they have recovered. As temperatures heat up, though, we’ll have trees that die.”
Petty said that he’s seen sycamores, rain trees,
Chinese tallow, elms and water oaks suffering damage, but live oaks and magnolia trees — both popular shade trees in the Houston area — are doing well.
The freeze affected trees’ cambium layer — essentially their vascular system — just beneath the bark. That layer is responsible for taking water up to the branches to be converted to sugars through photosynthesis. If a tree is so damaged that it cannot do this, it cannot feed itself.
Summer’s worst heat — when a tree needs to be able to replenish water and nutrients the most — will start wreaking havoc on trees.
“As it continues to warm up, a large number of trees and shrubs that we thought had recovered will die,” Petty said.
Barbara Fagan is one of Petty’s clients who removed a zombie tree — a river birch — and another damaged tree, a redbud, from her yard. Three holly trees took their place.
“It had a little bit of green on it, but it was losing more and more branches all of the time,” Fagan, who lives on the city’s west side, said of her river birch. “There’s a lot of really not attractive trees hanging around town.”
Petty urged her to take both trees out because they were more dead than alive and could cause unwanted damage if they toppled from a tropical storm or hurricane.
David N. Appel, a Texas A&M professor and a specialist in tree pathology noted that “zombie tree” isn’t a horticultural or agricultural term and showed restraint in using it.
He said that most trees with dead-looking branches and new shoots coming from the center could be zombie trees, but not all are. They’re certainly damaged trees, some of which will live and some of which will die, and it’s fairly obvious which branches should be pruned back.
“I’ve been from the Rio
Grande all the way up to Wichita Falls, and I have talked to a lot of arborists and one thing is clear: The damage was remarkably similar, it’s just that the species were different depending on where you are,” Appel said. “In one place you hear a lot about lace bark elms, but in another place it might be some of the oak species. In Wichita Falls it was the Japanese black pine and Mondell pine.”
Appel said Texas will lose hundreds of thousands, possibly millions, of trees.
“The picture has become much clearer than it was two months ago, but we still (won’t know the fate of ) a lot of these trees for a long while,” he said. “We aren’t out of the woods yet, and that’s not a tree joke.”
The 2011 drought prompted the loss of 40,000 trees in Memorial Park. Conservancy president and CEO Shellye Arnold and forestry supervisor Eric Hollenbeck both said that they’ve worked hard to restore the 1,500-acre Houston park to its natural state — a grassland prairie — by removing non-native plants and trees. New plantings, primarily natives, fared better in the freeze.
Tree experts at the city of Houston and Mercer Botanic Gardens in Harris County Precinct 4 both said they’re watching trees closely, removing them when they need to.
Jeremy Burkes, urban forester with the Houston Parks Department, said the loss of palm trees after the freeze was quick and visible. In a single week in May, city workers removed 23 trees that uprooted after heavy rains.
“We’ve already had a number of large mature trees completely fall over, comparable to what you would see in a hurricane. Trees of this size don’t just fall over, so we think it had to do with the freeze,” Burkes said. “If we have a drought and a hurricane, it’s going to be a lot worse.”
For now, Burkes and his team monitor city parks, looking for trees that are without foliage or with a significant amount of dead wood, a sign they’re in decline.
Chris Ludwig, Mercer’s executive director, said he and his staff have watched the trees on their property closely. Pines that lost their needles are pushing out new ones, and most trees are rebounding.
“Our trees that are suffering are trees that were suffering prior to the freeze. They were in a weakened way already, older trees,” Ludwig said. “Water oaks and other hardwoods are in danger. The Chinese tallows are struggling, but they’re an invasive species so we can stand to lose some of those.”
Ignoring damaged or zombie trees puts you, your home and your belongings — and maybe your neighbors, too — at risk during storms.
Homeowners can start by assessing their yards, looking for dead branches, peeling bark, fungus or any other sign that a tree is having problems. An ISA-certified arborist can assess a zombie tree and determine if the tree requires pruning or removal.
The problem won’t be over when 2022 arrives.
“Freeze damage will initiate heart rot problems 15, 20, 30 years from now. That takes decades to develop,” Appel said. “We’ve got that problem and we’ve got dead branches that are going to begin to decay … and become dangerous if a high wind comes along.”
As much trouble as shade trees are in, arborists are just as concerned about the more decorative palm trees still standing.
Dustin Beck, arborist and owner of Houston Tree Surgeons, compared palm trees to very tall bundles of millions of pieces of straw. With the 2021 winter storm, the water inside them froze and thawed and may be fermenting and decaying inside. One day, they’ll just die, falling to the ground or bending over near the top or middle of the trunk, seemingly without warning.
“All palm trees are transplants — none of them are native,” Beck said. “They are in serious danger of falling over.”
For safety reasons, Petty said that his employer has put a moratorium on climbing palm trees to prune dead fronds. If they can’t reach the top with a lift truck, they won’t deal with the tree.
“I’ve seen palm trees that on one day look healthy with green fronds and a couple of days later, the whole tree bends over like a shepherd’s crook. The trunks look solid, but because of decomposition and fermentation, they’re turning into mush,” Petty said. “I’m hearing reports of that all over Texas. San Antonio and Austin are both seeing it, and we’re seeing it in Houston, too. As the temperatures warm up, you’re going to see palms become a greater risk.”
David Mauk of the Jones Road Tree Service said his crews have removed more trees this year than any in his company’s history. He urges homeowners to hire professionals and launch a tree preservation plan for how to feed, water and prune their trees.
“I’m seeing more issues every week. I’m not a scorched-earth policy arborist, but if you have a tree with 50 percent canopy loss, you should remove it,” Mauk said. “As it gets hot and dry, you’ll see more (problems). Heat brings on stress and if we get a drought this summer, you’ll see an epic tree loss in Houston.”