Wednesday, June 01, 2011

May Day Tree Invasion - Obvious While Blooming

Riding home along the Chester Creek bike trail, it was clear that chokecherries - also known as May Day trees - were in bloom.  They were all white with blossoms, standing out starkly from the green birch and aspen and spruce.  Not only do you see them, but you can't help but breathe in their powerful fragrance.  Probably not fun for people with allergies.

They aren't native to Alaska, but do well here.  Too well as was clear along the bike trail.  

An Alaska Dispatch article  by Rick Sinnot from February gives more detail:
Chokecherry trees are not native to Alaska. We brought them here. Now tens of thousands of these trees adorn yards, parks, and roadsides in every part of the city. Three species are most common in Anchorage: Amur chokecherry, Canada red chokecherry, and May Day tree (or European bird cherry). May Day trees are highly invasive. They have escaped cultivation in Anchorage and are beginning to replace native trees, especially along waterways. A 2010 report on several municipal greenbelts by the Alaska Natural Heritage Program described dense thickets of bird cherry trees, in some areas replacing willows, which are a preferred forage for moose. Some riparian areas in Anchorage are already dominated by May Day trees in both the canopy and understory. Invasive plant specialists call this an infestation.

I had heard about this in past years, but what I didn't know is that they are poison for moose.

For all its imposing bulk and rugged good looks, a moose is a delicate creature. Its huge, four-chambered stomach, well adapted to digesting a winter diet of woody twigs, is particularly sensitive to physical and chemical agitations. Swallowing a few mouthfuls of chokecherry twigs, leaves or seeds can kill a moose in one to two hours. Calves are probably more vulnerable than adult moose because they are smaller.
The deadly ingredient in chokecherry foliage is cyanide gas: hydrogen cyanide or HCN. The cyanide is locked in plant cells, isolated from the enzymes that create the gas. However, wilting, freezing, crushing, and chewing (does this sound like what might happen to a plant eaten by a moose in winter?) releases the gas. So does digestion by the enzymes in a moose's rumen, the first of four chambers comprising its highly evolved stomach. A lethal dose of HCN causes rapid labored breathing, frothing at the mouth, dilated pupils, ataxia, muscle tremors, and convulsions. The moose usually dies within a few minutes of developing these symptoms. The cyanide stops cellular respiration, resulting in respiratory arrest. The moose suffocates.

On this gray day, the ones on the left don't come out as clearly as they do when riding by, but you can see the white near the front there.  They were scattered along the trail all the way I went from Valley of the Moon Park to Lake Otis.

Campbell Creek Trail website offers this suggestion for this and other invasive plant species:

Avoid purchasing, growing, or sharing invasive plants. For help contact the University of Alaska Cooperative Extension Service at 907-786-6300, or the Alaska Committee for Noxious and Invasive Plants Management at

1 comment:

  1. Oops. Planted one of the blighters in an Anchorage trailer court in 1988. Grew into a beautiful tree last time I checked in 2006. Moose didn't bother it. Now I know why.



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