Published: May 8, 2015
Numerous blossoms portend a rich harvest of chokecherries. Click here for larger image. Photo by Jeff Mitton.

By Jeff Mitton

Chokecherries are blossoming, filling the air with a pleasant fragrance and attracting pollinators.

Chokecherry, Prunus virginiana, is a small tree or shrub with an immense range, from the Atlantic to the Pacific in Canada and in most of the 48 contiguous states with the exception of those in the southeast.

This last weekend, I watched chokecherry blossoms for a while and noted repeated visits by a slender, dark bee of the family Adrenidae, colloquially referred to as mining bees. They are solitary bees with nests in the ground.

But the showy, open flowers attract a variety of pollinators, including honeybees, mason bees and bumblebees.

Cherries develop during summer and are approximately ¼-inch in diameter.

Unripe fruit are red, but they ripen to a deep purple or black in August and September. When they first become dark they are considered ripe, but they are still quite astringent or tart.

If they are allowed to ripen further on the tree, their tartness declines and the cherries on some trees become quite sweet.

Many species of wildlife are drawn to chokecherries, including numerous species of birds, raccoons and squirrels.

Our local opportunistic omnivores, black bears, are especially fond of chokecherries. Bear scat is easily identified because it is usually packed with fruit remains, most typically chokecherry, hawthorne and wild plum, which are all common in the foothills west of town.

Chokecherries were an important part of the diet of Native Americans, especially those living on the Great Plains.

Chokecherries were a staple and the most important fruit in the diet of Pawnee, Osage, Kiowa, Arikara, Ute, Crow, Cheyenne and Blackfoot.

Passing chokecherries through a bear scarifies the seeds and substantially improves their germination. Bears are eager to provide this service. Chokecherry invites pollinators with nectar and entices frugivores with conspicuous cherries, but it does what it can to deter herbivores by making its leaves poisonous.Pemmican, which includes chokecherries, was prepared by many Native Americans because it kept well, could be used as trail food and could be stored for times when winter weather prevented hunting or fishing.

Lean dried bison (or deer or elk or moose) was ground and mixed with dried and crushed chokecherries, then blended with hot fat. As the fat cooled, it was shaped into solid strips or bite-sized balls.

European settlers had many recipes incorporating chokecherries. They found that either drying or simmering chokecherries eliminated their bitterness and brought out a sweet flavor that formed the basis for jams, jellies, pies, juice, wine and syrup.

Chokecherries are not used today as commonly in the past, but I found online recipes for chokecherry pemmican, juice, apple butter, syrup and vinegar.

Chokecherries and other fruits are an inducement by the plant to get animals to disperse the seeds. Animals consume the fruit and then, some time later and some distance away, they defecate the seeds.

Passing chokecherries through a bear scarifies the seeds and substantially improves their germination. Bears are eager to provide this service.

Chokecherry invites pollinators with nectar and entices frugivores with conspicuous cherries, but it does what it can to deter herbivores by making its leaves poisonous.

Vacuoles in the leaves store cyanogenic glycoside, a molecule that combines cyanide and a sugar. The molecule is stable and harmless in an undisturbed leaf, but if a moose or deer chews the leaves, the vacuoles are shattered, bringing the cyanogenic glycoside in contact with an enzyme that cleaves the molecule, releasing hydrogen cyanide, a deadly poison.

In sufficient quantities, the leaves are lethal to all of the ruminants — moose, deer, bison, pronghorn, bighorn sheep and cattle.

Many plants, perhaps most plants, have chemical defenses. But I am not aware of any plants so well defended that they are able to deter all insect herbivores.

Tent caterpillars frequently colonize chokecherries — the infestations are conspicuous due to the large tents, hordes of caterpillars and defoliation.

Two-tailed swallowtail butterflies seek out chokecherries to lay their eggs, so when their larvae hatch they will have immediate access to their favored food source.

Jeff Mitton, mitton@colorado.edu, is a professor in the Department of Ecology and Evolutionary Biology at the University of Colorado.

May 8, 2015