Saxifrages are basal leaved plants with a tall leafless flower stalk. The Eastern Swamp Saxifrage is a native perennial herb.
The leaves are all in a basal rosette at ground level, hairy on both sides and on the margins, fleshy, lance shaped, obtuse at the top and narrow at the base to an indistinct stalk.
Inflorescence: After the leaves develop, a hairy (purple-tipped stipitate glandular hair), 1 to 3 foot tall flower stalk emerges, on which is a "lax thyrses" - a terminal cluster of buds that looks like a pine cone, which then opens into several small branches of flower clusters. A regular thyrses is roundish compacted panicle. (See Tufted Loosestrife as an example)
The flowers can number 30 to 50+ and are 5-part, each about 1/4 inch wide, with five creamy or whitish petals, without spots, lance shaped and outward spreading. The sepals are green, more triangular and reflexed. The 10 stamens have flattened filaments and orangish color anthers creating a club shape; the ovary parts are green with two pistils with styles that are joined together for the lower half of their length. The calyx tube is nearly free from the large ovary. In a few Eastern states of the U.S. a purple-petaled version may occasionally be found.
Seed: Fertile flowers produce a dry ovoid seed capsule whose tips diverge when the small brown seeds are mature for wind dispersion.
Habitat: M. pensylvanica requires moderate moisture at a minimum, marshes and bogs preferred and does well in full to partial sun. Habitat with less moisture will need more shade. The root system has thick fleshy rhizomes which can form offsets creating more plants.
Names: Recent work with DNA evidence and differences in the ovules and the pollen has resulted in this species being moved from the Saxifrage genus to the Micranthes genus within the Saxifrage family. Micranthes is derived from two Greek words mikros meaning 'small' and anthos meaning 'flower'. The species name pensylvanica, means 'of Pennsylvania'. The accepted author names of 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. His work was updated by ‘Haw.’, which refers to Adrian Hardy Haworth, (1767-1833) English botanist and entomologist, Fellow of the Linnean Society, author of Lepidoptera Britannica (1803-1828) and other works including Saxifragearum enumeratio.
Comparisons: Other members of the Saxifrage Family in the garden include Alum root, Foam Flower and Mitrewort. The only other species of Micranthes found in Minnesota is Micranthes virginiensis, the Early Saxifrage. It is only found in NE Minnesota in the Arrowhead and in Lake of the Woods County where our current species is not found. It has many differences including smaller leaves and is not rhizomatous.
Above: The inflorescence initially looks like a pine cone then opens into several small branches of flower clusters. 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: The leaves are all basal, with the flower stalk emerging soon after the leaves. Note the hair on the leaves and flower stalk.
Below: 1st & 2nd photos - The flower stalk opens side branches and then the flowers open. The stalk has purple-tipped glandular hair. 3rd photo - Seed heads form a dry capsule which opens when mature to release seeds via wind dispersion.
Below: An individual plant showing the basal clump and the tall flowering stem.
Below: An extensive group of Swamp Saxifrage in flower in the wetland at Eloise Butler. Water Horsetail (Equisetum fluviatile) in the foreground
Notes: Swamp Saxifrage is indigenous to the Garden area. Eloise Butler catalogued it on May 25, 1907. Martha Crone noted planting one plant in 1946. It has been on every Garden census since. It is native to counties of Eastern and Central Minnesota roughly east of a diagonal line running from Mower in the SE to Hubbard and Beltrami in the NW; absent in the Arrowhead. In North America it is found in the NE Quadrant of states from MN, IA, MO on the west and then east to the coast, as far south as TN and NC; in Canada in Saskatchewan, Manitoba and Ontario. The plant is listed on the endangered or threatened list in IN, ME, RI and TN. There is no mention of this plant in folk or medicinal literature. There are 45 species of Micranthes in North America.
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"