Wild Plums, Grapes, and Cranberries

Wild plums

American plum (Prunus americana) forms thorny thickets along woods edges, fencerows, and stream banks across southern and central Wisconsin; Canada plum (Prunus nigra) is similar and more northern.

• Spring: masses of white, fragrant blossoms in early May, before the leaves.
• Fruit: round plums about an inch across, ripening red to yellow-orange in late August and September.
• Flavor: sweet, juicy flesh under a tart, astringent skin.

Shake the trees over a tarp when the plums are soft, or pick up windfalls daily. They’re superb in jam, jelly, and plum butter, where the skins give tartness and color, and in sauces for pork and game. Cook them and push them through a food mill to remove the pits and skins.

Plum pits, like cherry pits, contain cyanogenic compounds. Don’t crack and eat them.

Wild grapes

Riverbank grape (Vitis riparia) is the common wild grape in Wisconsin, climbing over trees and fences along rivers, woods edges, and roadsides.

• Vine: woody, with forked tendrils that coil around supports; bark shreds in long strips on old vines.
• Leaves: large, toothed, heart-shaped, often with three shallow lobes.
• Fruit: small, blue-black grapes with a waxy bloom, in clusters, ripening in September. They’re intensely sour and seedy; they sweeten a little after frost.

Wild grapes make excellent jelly and juice. Simmer them, strain, and let the juice settle overnight so tartrate crystals drop out. Young leaves can be used for stuffed grape leaves.

Moonseed

Common moonseed (Menispermum canadense) grows in the same places and has fruit that looks like a wild grape. It’s highly toxic: its alkaloids cause convulsions and can be fatal ¹. Learn the differences ¹:

Cut a berry open before picking a vine you’re not certain of. One flat, crescent-shaped seed means moonseed. Also check for tendrils.

Virginia creeper’s dark blue berries on red stalks are also toxic; its leaves have five leaflets.

Highbush cranberry

Highbush cranberry isn’t a cranberry; it’s a viburnum. The native American highbush cranberry (Viburnum trilobum, or V. opulus var. americanum) grows in moist woods, swamp edges, and thickets across Wisconsin.

• Leaves: opposite, three-lobed like a maple.
• Flowers: flat white clusters in June, ringed with large sterile flowers.
• Fruit: translucent scarlet berries in drooping clusters in September, staying on the shrub into winter.

The berries are tart and musky, with a large flat seed; cook them into jelly or sauce for game. Their smell while cooking is strong; many people find the jelly far better than the kitchen smells suggest.

The catch: European highbush cranberry (V. opulus), widely planted in yards and parks, is very hard to tell from the native plant, and the two hybridize. Its fruit is intensely bitter, while the American plant’s is tart but edible ². Taste a berry; if it’s unpleasantly bitter, try another shrub.

True cranberries

Large cranberry (Vaccinium macrocarpon) and small cranberry (Vaccinium oxycoccos) are low, creeping evergreen shrubs of sphagnum bogs in northern and central Wisconsin, the wild relatives of the state’s big cranberry crop.

• Plants: thin, trailing stems with tiny, leathery, evergreen leaves, running over moss.
• Fruit: red berries in late September and October, staying through winter.

Walking a bog is its own adventure: the mat is floating moss, so step carefully near open water and wear waterproof boots. Use wild cranberries as you would cultivated ones.

Wild fruits are allowed on DNR land for personal use ³.

What to take from this

American plums ripen red to orange in late summer, tart-skinned and best as jam and plum butter. Riverbank grapes climb with tendrils and have round seeds; moonseed twines without tendrils and has one crescent seed and is deadly, so cut a berry open. Highbush cranberry is a three-lobed viburnum with scarlet berries for jelly; the European kind is bitter. True cranberries trail over northern sphagnum bogs.