Researchers work on chokecherry tree problem

Published: Sep. 2, 2021 at 6:06 PM AKDT
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ANCHORAGE, Alaska (KTUU) - Anchorage’s parks have been invaded by the chokecherry tree. The trees were originally brought to Alaska for residential areas in the 1950s and ‘60s.

“We were looking for good horticultural opportunities with trees,” said Gino Graziano, invasive species and forest health manager with the University of Alaska Fairbanks Cooperative Extension Service. “And this thing grows real fast. It’s pretty. The moose typically don’t eat it, so you don’t have to put a fence around it, so we started promoting it. Everybody promoted it.”

Graziano said they weren’t thinking about invasive species at the time.

“Around the early 2000s, late ‘90s, people started noticing it out in the forests and the problem has slowly gotten taller and taller until now we have a lot of mature, reproducing trees out here,” he said.

The chokecherry tree is found outside Alaska as well, but Graziano said the problem isn’t as bad in other places.

“Cherry trees tend to form these dense thickets at times, but in Alaska this seems to be pretty extreme, like you don’t see this when you go down to Oregon or Washington where there’s native chokecherry trees,” Graziano said. “And I think it’s because we don’t have the insects and diseases and herbivores that can keep this under control.”

The chokecherry tree is efficient at reproducing and spreading.

“It creates this really dense shade layer, and that seems to help it out-compete other vegetation,” Graziano said. “So when you walk into a forest like this where you’d normally see currants and dogwood and the high bush cranberries, those are virtually gone. We think a lot of that is from the shade. The other thing that helps it compete is, it’s actually toxic to moose. Moose typically avoid browsing it. They’ll occasionally eat it and that’s one of the reasons we know it can be toxic to them, but they typically avoid it, so that gives this tree a competitive advantage over the others.”

Moose aren’t the only animals impacted by the chokecherry tree. Salmon will possibly be affected as well.

“There’s actually a study that a graduate student at UAF did that pointed out that this tree supports far fewer terrestrial insects and those terrestrial insects that fall into streams make up 20 to 30% of a young salmon’s diet,” Graziano said. “So there could be potential impacts down the line on the food web in these creeks that get overrun with chokecherry.”

In a forest park in East Anchorage, Graziano and some other researchers with the Cooperative Extension are setting up a study to learn the best way to kill the chokecherry trees without killing everything around it.

“What we’re doing here is setting up our plots — each one is a 6-meter square. Then what we do is go through and count all the trees that are a little over 2 feet tall, those are about treatable size,” Graziano said. “We count both the cherries and the native vegetation. We go through and make our treatments to kill off those trees that are treatable and then we wait and see. And in a year, we’ll know how that vegetation changes, how well those herbicides work on those chokecherry trees, and how the vegetation is responding, to come back, hopefully,”

Anchorage isn’t the only place with a chokecherry tree problem.

“We’re finding it more and more in other communities outside of Anchorage,” Graziano said. “Talkeetna’s doing some work with theirs, in their local forest. Hope, Homer, Soldotna, Kenai, and then the Fairbanks area, as well.”

Graziano said they know about the chokecherry trees in Anchorage parks, but if people see one outside of Anchorage, such as Chugach State Park or other natural areas, they would like to know about it. People can report the sighting on their mobile app, Alaska Weed ID. It’s free to download.

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