Wild Mint is an erect or ascending native perennial forb, growing to 2-1/2 feet high on 4-angled green hairy stems that have little branching. Sprawling of the stems is common.
The leaves are opposite, stalked, ovate to lanceolate (widest below the middle) in form with toothed margins, pointed tips, well defined vein patterns and may be smooth on the upper side but usually with fine hair on the underside. Leaves and stems are aromatic. Leaf pairs are 90 degrees rotated from adjacent pairs.
The inflorescence consists of dense whorl-like axillary clusters of flower heads that appear above the axils of the upper leaves - but not at the top of the stem. These clusters are distinctly separated from each other on the stem. In the mint family this arrangement is called a 'verticillaster' where the flowers look like a whorl arrangement but are actually in cymes that rise from the axils of a pair of opposite green hairy bracts. Only a few flowers in each cyme open at one time.
The individual flowers are tubular, from 1/8 to 1/4 inch long, and irregular in form. The petals of the corolla vary in color from white to light purple or pink. The upper lip of the flower, formed from 2 fused petals, is divided into two lobes or just notched in the middle. The lower lip, formed from 3 fused petals, is singular or subdivided into 3 lobes. There are four stamens and a style which protrude from the corolla tube, the base of which inside has long white hair. The green to purplish calyx is usually hairy with visible darker veins and the tip has awl shaped or triangular lobes. The calyx tubes of the flowers are often shorter in length than the length of the stalk of the adjacent leaf.
Seeds: Fertile flowers produce a small nutlet containing one brown oval seed, 1 mm long, that has a small pointed tip. The small seeds need light to break dormancy so should be surface sown. Seeds do not need cold stratification.
Varieties: See notes at bottom of page.
Habitat: Wild Mint is a common mint family plant of moist meadows and moist areas around marshes and streams. It grows from rhizomes and spreads by rhizome growth, forming colonies. Full sun is preferred, partial shade tolerated.
Names: In Eloise Butler's day this variety was simply known as Mentha canadensis. The genus, Mentha, is named for the classical mythology Greek nymph Minthe, who was unfortunate enough to be turned into a mint plant by Persephone (Hades wife) so Minthe could avoid seduction by Hades, which was something Persephone feared Minthe wanted. The species, arvensis, means 'of the planted fields' which is a habitat the plant can be found in, hence the alternate common name of Field Mint.
The author names for the plant classification are: First to classify was '(L.)' which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. For the variety, Linnaeus is given credit for his early work but additions to the classification were added by ‘Kuntze’ which is for Otto Kuntze (1843-1907) German botanist, who edited the collections in Berlin and Kew Gardens and then published Revisio Generum Plantarum which laid out new rules for nomenclature which were rejected at the time, but some acceptance came long after his death.
Comparisons: While other cultivated mints have the same aroma, Wild Mint is distinguishable by the whorl-like arrangement of flowers, separated along the stem, without a group at the stem top. Two other similar looking species, but always with white flowers, are Northern Bugleweed and American Water Horehound. Both are found in the Garden. The most closely related Minnesota species is the Hairy Wood Mint, Blephilia hirsuta, but that is only found in the wild in 5 SE Counties. It has more hairy leaves, larger corolla lobes, the lower corolla lobes have dark purple spots, and there is a verticillaster at the top of the stem also. See also Downy Wood Mint, Blephilia ciliata, which is not native to the State but similiar to B. hirsuta.
Above: The characteristic whorl-like arrangement of flowers in the leaf axils. These structures are composed of cymes and the structure is called a 'verticillaster'. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: Wild Mint flowers are irregular in shape, with the lower lip frequently divided into 3 lobes as seen here; the upper lip sometimes 2 lobed or simply notched. Note the hair in the corolla throat.
Below: 1st photo - The hairy calyx has darker colored veins and awl shaped tips. 2nd photo - A nutlet forms from each fertile flower. Each contains one seed.
Below: The seed capsule of Wild Mint retains the awl shaped tips of the calyx. The individual brown seeds are much smaller than the capsule.
Below: Leaf edges are toothed and the underside (right) hairy. The vein pattern is prominent.
Below: Wild Mint will form colonies from its rhizomes.
Notes: Wild Mint is indigenous to the Garden. Eloise Butler catalogued it on May 31, 1907. She also planted a few more on June 9, 1913, that she obtained from 4748 Chicago Ave. in Minneapolis. It was also placed around the new Mallard Pool in 1932. Wild Mint extensively covers North America with only the far north of Canada and a few of the southern states of the U.S. not reporting it. Likewise, within Minnesota there are only a few widely scattered counties where it has not been found.
Varieties: There are eight recognized varieties of M. arvensis. M. arvensis L. var. canadensis is the variety found in Minnesota. This is the only native species of the Mentha genus found in Minnesota, but there are two introduced species present also - M. spicata, Spearmint, and Mentha ×gentilis, Heartmint. A third introduced species, M. aquatica x spicata, Peppermint, has been reported but never collected in the wild, but it is the only other Mentha in the Garden's collection. The other two species called mints - Downy and Hairy Wood Mint - are in the Blephilia genus.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"