Bergamots all have flowers in dense heads with the stamens and style protruding from the corolla throat.
Varieties: There are two subspecies native to and present in Minnesota noted by the U of M Herbarium - Monarda fistulosa L. subsp. fistulosa, which has mostly branched stems in the inflorescence and longer leaf stalks; and second is subsp. menthaefolia, (known as Mintleaf Bergamot) which has mostly unbranched stems and short leafstalks with leaves more narrowly elliptical with less coarse teeth. The DNR does not distinguish between varieties on its county location list, but the Great Plains are the dividing line between the two subspecies with subsp. fistulosa trending eastward and subsp. menthaefolia trending west and north. Flowers are the same. Photos here are of subsp. fistulosa.
Stems: Wild Bergamot grows upwards to 3+ feet high on typical 4-angled mint family green hollow stems (reddish with full sun at maturity) that in subsp. fistulosa branch in the upper half and are mostly hairless though they can have some gray hair at the nodes.
Leaves are opposite, stalked, have a gray appearance, are lance shaped with a triangular base, and have a main rib-vein with branched side veins curving toward the leaf margin which is serrated. Teeth are less noticeable or absent on upper leaves. Subsp. fistulosa has longer leaf stalks and coarser teeth. Leaves may have hair also on the stalk groove. The green parts of the plant have a distinctive aroma of oregano when crushed. The Bergamot that is an ingredient in Earl Gray Tea is not this plant, but Mentha citrata. See also, Eloise Butler's notes below.
The inflorescence in subsp. fistulosa is a branched panicle, taller than wide. Each branch has a single flower head, 1 to 3 inches wide, dense with numerous unstalked florets. Sometimes additional branches appear from the an upper leaf axil. Subsp. menthaefolia has little branching.
Flowers: The florets are tubular, pink to lavender, with corollas of 5 petals that form 2 lips - one lip formed from two fused petals forming an elongated tube that rises upward and surrounds and protects the 2 stamens and the style, which protrude above that upper lip. Three fused petals form one wider but much shorter lip below. Stamens have lighter color anthers with a darker marginal line and the style has fine white hair. The outer surface of the corolla lips have fine hair. The calyx tube is shorter than the corolla, greenish then to deep pink when mature, with five pointed lobes. Flowers open from the center of the head first and progress to the outer edge. Under the flower head are green bracts that can have a pinkish tinge. The flower stem has fine white hair.
Seeds are a very small brownish-black dry nutlet, ovoid/cylindrical in shape with one end bluntly rounded, the other end more pointed. Each floret will usually produce 4 seeds. These will germinate upon planting without any special pre-treatment.
Habitat: Wild Bergamot likes full sun with moist to somewhat dry conditions. With good moisture and rich soil the plant puts on much vegetative growth and becomes sprawling. Best plant appearance will be with average soil and moderate moisture. Leaves are subject to mildew. The plant grows from a rhizomatous root system that produces multiple stems in a cluster, but does not produce stolons, so the plant does not spread aggressively, but simply enlarges the clump. It spreads mainly by re-seeding. Plants are long-lived. Long-tongued bees and butterflies love the plant.
Names: The genus name, Monarda, is an honorary for Spanish botanist Nicholas Monardes (1493-1588) who published a book in several editions on medicinal plants of the new world. The species fistulosa, means 'hollow' referring to the plant stem of this species. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparison: There are many plants of Wild Bergamot in the Upland Garden. There are many fewer of the more eastern native U.S. species - Purple Bergamot, Monarda media Willd., which is not native to Minnesota and which differs from M. fistulosa by its darker reddish-purple color. Purple Bergamot tends to bloom earlier than Wild Bergamot. There are ornamental cultivars available from the nursery trade which could ultimately escape to the wild. These usually resemble M. fistulosa except in flower color - the most common cultivar comes from Scarlet Beebalm, Monarda didyma, and is the deep red one called called 'Raspberry Wine'. Both are shown below.
Above: The stem of Monarda fistulosa L. subsp. fistulosa has branching at the top in the inflorescence. 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: A grouping of Wild Bergamot in late July - early August. The root system can produce multiple stems and enlarge by rhizome spreading.
Below: The hollow stem is enlarged at leaf nodes and is taking on a reddish color typical of sun exposed stems.
Below: A flower head of Wild Bergamot. Note the flowers are tubular, pink to lavender, with corollas that have the upper lip forming a tube that surrounds and protects the 2 stamens and the hairy style. Beneath the head are green leafy bracts.
Below: The outside of the calyx and the corolla has fine white hair. The calyx tube is green initially, turning dark pink at maturity. Florets open from the center of the disc first.
Below: The leaf structure of the Bergamots - note that the larger lower stem leaves like the one shown can have a pair of smaller leaflets in the axil.
COMPARISONS: Two color variations of Wild Bergamot are shown below. 1st photo is Purple Bergamot, Monarda media. 2nd photo is a nursery trade cultivar of Monarda didyma called 'Raspberry Wine'.
Below: The seeds are angled with one end pointed, the other more rounded.
Notes: Wild Bergamot is indigenous to the Garden area. Eloise Butler catalogued it on Sept. 6, 1907. She planted 2 in Oct. 1919. Martha Crone planted it in 1945 during the development of the Upland Garden and Cary George noted planting it in 1995.
The University of Minnesota Herbarium lists three species of Monarda in Minnesota; the other two are M. punctata, Spotted Beebalm, and M. didyma, Scarlet Beebalm, although the DNR does not have a location for it currently and it is probably no longer in the state. In North America Wild Bergamot, in its various subspecies, is found throughout except for the Alaska, California, Florida and most of the very far north Canadian Provinces.
Eloise Butler wrote of this plant: "Mrs. Mable Osgood Wright, in her The Garden, You and I, describes a fascinating garden designed by an invalid lady, in which nothing was admitted but plants with fragrant flowers or leaves. In such a garden, the mints would abound, and among them would be Monarda fistulosa, the Wild Bergamot, that now enlivens the borders of woods and meadows with large clumps of bright lavender bloom. Abundant as it is, we are never ready to cry “Hold! Enough!” For, besides its delicate perfume, it delights the eye as well. This plant will at once remind one of the cultivated, red-flowered bee balm or Oswego tea (Monarda didyma). The mints may be recognized by their square stems, two-lipped flowers, and usually aromatic odor." Published July 23, 1911, Minneapolis Sunday Tribune
Medicinal Lore: Monarda plants besides having some of the taste of oregano on fresh growth, contain a substance called thymol, which is an antiseptic compound used in such products today (although manufactured) as mouthwash. This compound is why native Americans were able to use the plant as Densmore describes in her book on the Minnesota Chippewa (Ref. #5). The flowers and leaves were boiled to make a tea like brew in which children with skin burns and disruptions would bath in. Also, dried flowers and leaves, powdered and then moistened with a little water would be applied to a burn - said to be especially effective for scalds. Densmore refers to the older scientific name, M. mollis, which today, is considered to be within M. fistulosa L. subsp. fistulosa.
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"