Purple Marshlocks is a native semi-erect perennial forb, growing up to 40 inches long with decumbent stems that are somewhat woody at the base. The upper stem rises from the ground level section and can root at the nodes. It usually has woolly hair. Sheaths form where stems divide.
The leaves are pinnate with 5 to 7 leaflets on the lower leaves, fewer leaflets up the stem to just a palmate leaf at the top. Lower leaves are on long stalks, upper leaves almost stalkless. Leaflets are oblong to oval, sharply toothed, tips somewhat rounded, bases narrowed. On large lower leaves the lower leaflets may be separated from the others. The upper surface green, the lower surface is whitish. Leaves and stalks often age by picking up the color of the flower. A pair of large stipules are at the base of the leaf stalk.
The inflorescence is a terminal solitary flower or a cyme with 1 to 10 flowers.
The flowers are showy with the 5 calyx lobes (sepals) reddish to purplish and longer than the 5 petals, surfaces hairy. The outer (underside when open) surface is greenish-purple with purple veining. The lobes are ovate with pointed tips. The sepals spread outward making the flower 1 to 3 cm in width. The 5 petals are similar in shape with slightly darker color, but much smaller. There are 5 small much shorter bractlets just beneath the sepals. Stamens number 20 to 25, have purplish filaments with dark-purple anthers. They rise from a large spongy area of the torus ring at the top of the hypanthium. In the center is a cluster of numerous carpels with styles. It is possible to find plants where the petal and sepal count is more than 5.
Fruit: After fertilization, the sepals fold forward into a 5-angled capsule shape, the torus enlarges and a number (up to 30 or more) of ovoid but slightly flattened achenes develop -- the entire structure somewhat in the form of a strawberry. The achenes have the now reflexed style still attached. When mature the sepals open again. The achenes are small, 1.3 to 1.6 mm, smooth, brown at maturity and do not all separate from the structure at the same time.
Habitat: Purple Marshlocks grows in the sunny environments of moist meadows, stream banks, near shallow ponds and in bogs. The stem can tolerate standing water The root system is rhizomatous with long thin rhizomes and with stolons forming the above ground stems.
Names: In earlier years Purple Marshlocks was classified as Potentilla palustris. The current classification now has the genus name Comarum which is from the Greek kŏmaros, the name for the strawberry tree and used because the fruiting head resembles a strawberry. The species palustre means 'marsh loving', a place where the plant is usually found. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. The common name of 'marshlocks' is a bit obscure.
Linnaeus originally had created a section in Potentilla, in 1753, called Comarum where he located this plant. Thus, he retains authorship. The genus Comarum was established to contain species where the fruiting structure is in-between that of Potentilla where it was formerly placed, and the Fragaria (the strawberries) where it is too different to be included there, although it has been hybridized with Fragaria. There are only 5 species world-wide in this genus and C. palustre is the only species in North America.
Comparisons: Purple Marshlocks is easily identified when in flower. Prior to flowering the palmate leaf may resemble other cinquefoils in the Potentilla genus, many of which have yellow flowers.
Above: The inflorescence is one to a few stalked flowers atop the stems. 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: 1st photo - The colorful sepals are much longer then the short petals which appear here between but placed above the sepal lobes. The stamens arise from the central spongy material and in the center are the numerous carpels each with a style. This section enlarges in the fruiting stage. 2nd photo - the large sepals are hairy and are greenish with purple veining on the underside. Just beneath them and shown here pointing downward are 5 small pointed bracts. Flower stalks and upper stem parts are all hairy.
Below: The horizontal creeping stem shown with a leaf rising from it and the stem turning upward to form a flowering stalk.
Below: 1st photo - a leaf with widely separated lower leaflets. 2nd photo - the pair of stipules with an unstalked 3-part leaf above. 3rd photo - the sheath at a stem node.
Below: 1st photo - the leaflet underside is pale in color with a reticulated vein pattern. Short whitish hairs on the mid-rid. 2nd photo - another view of a stem node sheath.
Below: 1st photo - after flowering, the sepals close again, with the enlarged torus and achenes developing inside. It is the inside structure that is similar to the structure of the strawberry. 2nd photo - immature achenes with the style remnants. At full maturity they are brown.
Notes: Eloise Butler introduced Purple Marshlocks to the Garden on Oct. 16 1909 with plants sourced from the Quaking Bog in Glenwood Park (within which park the Garden was located). She added more plants in 1910, '16, '17, '21, '24, and '30. Martha Crone first planted the species in 1933, 3 in 1945, more in '47 and '48, but by the time of her 1951 plant census she did not list it.
In Minnesota the DNR surveys report the species in 50 of the 87 counties, with the exceptions mostly in the west and southwest part of the state. It is the only species of Comarum in Minnesota or in North America where it is found north of the central part of the U.S., absent in the southern and southwestern states, and found in all of Canada. It is a circumboreal plant.
Medicinal Use: There is little information on folk medicine use of the plant other than it was used for healing wounds and treating lung and joint problems. Some recent work in Europe indicates that the rhizomes are possible source of Proanthocyanidins with antiarthritic activity (Buzuk, G. N.; Lovkova, M. Ya.; Ershik, O. A.; Sokolova, S. M., Doklady Biochemistry & Biophysics, July 2008).
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"