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Vt. Leaf Mystery Stumps Officials

  • Leaf stem damage on an oak tree growing near a Woodstock, Vt., parking lot has tree experts scratching their heads. (Jim Esden photograph)



Valley News Staff Writer
Monday, September 03, 2018

Woodstock — A mysterious form of leaf stem damage on an oak tree growing at the edge of a parking lot along Route 4 has tree experts in Vermont scratching their heads.

“We’re still clueless,” said Jim Esden, a forester with the Vermont Department of Forests, Parks and Recreation.

While in the Bridgewater Mill parking lot, Esden noticed a cluster of brown, dead leaves and took a closer look.

Such clusters are fairly common, often representing a twig or small branch that has been broken by the wind or some other natural force, but in this case, Esden was struck by how the leaf stems — known in the naturalist world as petioles — had separated into individual strands, like the fibers of a frayed rope.

Esden didn’t see any reason to think that the tree’s life is threatened by the damage, which is localized and has not affected neighboring trees, but his interest was piqued.

Esden took pictures of the find and sent them to other forestry experts around the state to see whether they could account for the mystery.

“One explanation,” he speculated, “might be that squirrels trying to get at young acorns at the end of twigs caused damage to the petioles in the process.”

Hartford Tree Warden Brad Goedkoop called the squirrel theory “a pretty good one,” and said he has come across the “strange effect” of frayed petioles from time to time.

Jon Bouton, who formerly worked as Windsor County forester, said he most recently came across frayed oak petioles last year, near the Fairy House Village at the Vermont Institute of Natural Sciences in Quechee.

“Maybe the young fairies are hanging on them and twirling around, sort of like what human children do with tire swings,” he joked.

While fairies are a long shot at best, Bouton said that at least one real-life population does find a use for the dead leaves hanging on oaks — “some species of small bats climb up into clusters for shelter while sleeping during the day,” he said.

Bouton and Kent McFarland, a biologist with the Hartford-based Vermont Center for Ecostudies, both suggested the unusual frayed petioles might have something to do with a feature of trees in the oak family that is unique among hardwoods — marcescence.

That’s the word to describe the process of withering, without falling off.

When cold weather comes, most hardwoods begin building up a layer of scar tissue where the leaf stem joins the twig; eventually, the juncture is weakened until the leaf floats groundward, McFarland said.

But the oak family — which includes oaks, beeches and hornbeam trees — does not build up that scar tissue, and its undisturbed leaves can persist into the following year.

“Normally the wind or the ice load would rip them off,” McFarland said.

McFarland suggested that perhaps, when very localized, branch-specific conditions are just right, the wind could dry out and twist the petioles in such a way as to create the frayed rope effect.

“It’s just a wild guess,” he said.

Aside from the photographs that Esden sent around, McFarland has never seen frayed petioles.

“No,” he said. “But I’m going to look for them now.”

Matt Hongoltz-Hetling can be reached at mhonghet@vnews.com or 603-727-3211.