The Penthoraceae family contains only one genus, which has two species world wide. Ditch Stonecrop is a native, erect perennial forb, growing on stout stems from 6 to 24 inches high. Stems have fine vertical ridges, stipitate glandular hair, the glands reddish-brown to purple tipped. Hair may be sparse on the lower stem. Stems are greenish-pink to pinkish during the growing season and bright red at maturity. They are simple or branched just beneath the inflorescence.
The leaves are alternate on the stem, lance-shape to elliptical shaped, tapering to a pointed tip and tapering a bit more abruptly to a base that meets the stem - no stalk. Margins are sharply toothed. There is one central main vein and upward curving laterals. The underside can be smooth to having sparse glandular hair.
The inflorescence is a branched cyme with 2 to 7 branches. Each branch can be 2 to 3 forked. Flowers are on one side of the branch only. Each branch with 10 to 25+ flowers. The branches extend as flowers open, are erect to ascending with a crook-shape curve, like a scorpion's tail, at the end of the fully extended branch.
The individual flowers are cylindric, only 1/4 inch wide, the hypanthium wider than long, stalks are very short and stipitate glandular. Petals are greenish-white and inconspicuous or missing entirely, instead you see 5 triangular to ovate sepals, erect to spreading with pointed tips. They are greenish to pinkish, turning red at maturity. The sepal margins are interesting - they are either entire or have 1 to 4 gland-tipped fine teeth per side of the sepal (photo below). The sepals are shorter than the central part of the flower, which has 5 carpels, connected to each other at their bases and sides. Each has a style whose stigma has a blunt tip. Ten stamens with short white to pinkish filaments are evenly spaced around the outside of the carpel ring. With maturity, the anthers turn pinkish to purplish and fall away and the stigma turns purplish. In the Autumn, in our area, the entire structure turns reddish.
Seed: Fertile flowers produce five flattish capsules which open below the style when mature. The capsule has a distinct beak, the remains of the style. Each capsule contains numerous tiny seeds have reddish to pinkish tubercles. Tubercles help the light seed float on water. Seeds need 60 days of cold stratification for germination plus light, so they should be surface sown.
Habitat: Ditch Stonecrop grows from a rhizomatous root system which can produce stolons. It grows in moist wet areas with plenty of sun. Standing water is tolerated.
Names: The genus Penthorum is from two Greek words, pente, meaning 'five' and horos meaning a 'boundary or limit'; thus obtusely relating to the 5 -part structure of the flower. The species sedoides means 'resembling sedum.' Sedums are commonly called Stonecrops. 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 Penthoraceae family is of recent origin. Ditch Stonecrop has been previously included in the Crassulaceae family. There are only two species of Penthorum world-wide - the current species and one found in Asia.
Above: The inflorescence is a cyme with curving branches. 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 - Flowers are arranged on one side only of the cyme branch, which has gland tipped hairs. Note the scorpion tail crook to the branch. 2nd photo - the stem, especially the upper section, has gland tipped hairs, sometimes with reddish-brown or pinkish tips as seen here.
Below: 1st photo - the unusual flowers have five distinct but attached carpels, each with a blunt tipped style. Ten stamens surround the carpels and on the outside are 5 green, hairy sepals with triangular lobes - the lobes can have up to 4 small gland tipped teeth as seen here. 2nd photo - two flowers shown after pollination, the anthers of the lower flower fallen away and the stigma of the style taking on a purple tinge, the same color as the sepal tips.
Below: A stalkless stem leaf and 2nd photo - the underside of the leaf, both sides smooth.
Below: 1st photo - a cyme branch at Autumn maturity, the scropion tail crook still present. 2nd photo - detail of the 5 carpels, styles still attached, prior to opening to dispense seed.
Below: A top view of Ditch Stonecrop, this one growing in standing water.
Below: A view of the same plant as shown above, one month later, in Autumn colors.
Notes: Ditch Stonecrop could be considered as indigenous to the Garden area as Eloise Butler found it growing there in 1916. However, prior to that she planted 12 plants on Sept. 16, 1914 from Lake Johanna (Ramsey County, MN). So its possible the 1916 discovery came from seed of the 1914 plants. She then planted it again in 1918, '22, and '26. Martha Crone noted planting it in 1933. It was not listed on her 1951 plant census. Ditch Stonecrop is found in North America from the Great Plains eastward to the Atlantic, and also in Washington, Oregon and British Columbia. Within Minnesota it is found in 64 of the 87 counties with most of the exceptions being in a "C" shaped curve beginning in Clearwater County and then South along the north side of Minnesota River, then to Dodge County in the South. This is the only species of Penthorum in Minnesota. and 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"