Wintergreen (Gaultheria procumbens)

You may have heard that wintergreen oil has medicinal properties, or that it is used to flavor candies and tea, but did you know that wintergreen grows wild in Minnesota?

Appearance. Wintergreen is a dwarf, ankle-high shrub with thick, shiny, evergreen leaves 1-2 inches long. They stay green all year, even under snow. In midsummer wintergreen produces small, white, urn-shaped flowers. They are no more than a half inch long and hang downward, out of sight. Once pollinated, a flower develops into a red berrylike fruit called a capsule. The fruit ripens in late summer and autumn. It is about the size of a large pea and has a strong taste of wintergreen, but fruits are rarely produced in abundance and in some years can be very hard to find.

Range. Wintergreen is found in forests across much of the northeastern United States and adjacent parts of Canada. In Minnesota, wintergreen is not uncommon in the northern and central forested parts of the state, though it is easily overlooked by the casual hiker.

Habitat. Wintergreen favors dry, sandy, acidic soil with a thin layer of humus derived from decomposing pine needles. It is most often found on level terrain under a canopy of jack pine, red pine, or northern pin oak, amid a significant ground layer of mosses or lichens, and frequently blueberries or bearberries.

Ecology. Wintergreen flowers are pollinated by bumblebees. Once pollinated, a flower develops into a red fruit that stays on the plant through winter, unless eaten first. Although the fruit of wintergreen is only a minor source of food for fruit-foraging birds and mammals, it may be important in the winter when few other berries are available. The fruit contains seeds that the animals spread when they eat it. But wintergreen can survive quite well without spreading seeds. This is because of its rhizomes. Rhizomes are tough, woody stems that grow horizontally just below the duff layer. As the rhizomes grow, they send roots downward into the mineral layer and leafy shoots upward to catch light. As the rhizomes continue to grow, a sizable colony can develop, sometimes even a carpet several feet across.

Human Uses. Over the years people have found a variety of uses for the distinctive taste of the berries, including candies, ice cream, and toothpaste. Humans can eat the raw berries, but some people will find the strong, minty taste bitter and unpleasant, and more than a small amount is toxic. The thick evergreen leaves are sometimes made into an herbal tea or used for folk medicine. Wintergreen’s pain-relieving properties are purportedly similar to aspirin, although no scientific evidence supports medicinal use. Commercial and medicinal wintergreen is now made synthetically rather than harvested from the wild.