French grass is a leafy, much-branched perennial that, despite its name, looks nothing like a grass. It grows in eastern Missouri.
The flowers are in loose, upright spikes; small, pale blue to purple to white, on long stems from leaf axils. Blooms May–September.
The leaves are on long stems, trifoliate (compound with 3 leaflets), with short hairs on the lower surfaces, the middle leaflet on a longer stem. Leaflets ovate, with smooth edges, pointed at both ends, to 4 inches long and about half as wide. Overall, the foliage strongly resembles that of soybeans.
The fruit is a single-seeded, oval bean pod about ½ inch long.
Similar species: Sampson’s snakeroot (O. pedunculatum, formerly Psoralea psoralioides) is a slender plant with blue-purple or whitish flowers on very long stalks, and leaves on short stems with narrow (½ inch wide), elliptical leaflets, the center one on a longer stem than the laterals. It blooms May–July. It is found on acidic soils in open woods and rock outcroppings south of the Missouri River.
Height: to 2½ feet.
Eastern Missouri.
Habitat and Conservation
Occurs on rich wooded slopes, low open areas, river banks, and valleys. Often grows in colonies from its creeping rhizomes.
French grass, although not threatened nationally, has become quite rare in several states, where it occurs in prairies. Its decline represents a contraction of its broad former range, which is due in large part to the loss of its prairie habitat. Most lands that had once been prairies have been converted to agriculture.
Status
Native Missouri wildflower.
Human Connections
French grass is among thousands of species of wildflowers in North America. Together, they provide a rainbow of color and a bewildering variety of shapes, sizes, and forms. In addition to their beauty, wildflowers support pollinating insects that also pollinate our food plants. The plant/insect food chain is critical for birds, mammals, and other larger animals to survive (including us).
Ecosystem Connections
Many kinds of insects visit the flowers, including various types of bees, wasps, flies, butterflies, and moths. These insects are important foods for birds and other wildlife.
In Missouri, where it grows on rich wooded slopes, low open areas, river banks, and valleys, French grass and its networks of creeping rhizomes help to stabilize soils against erosion.
In 2012, an overlooked, new species of flower moth caterpillar was found feeding on French grass. The species, which people are calling the French-grass flower moth, has not yet been described scientifically and is referred to temporarily as Schinia nr-jaguarina. In 2023 members of the St. Louis-area Webster Groves Nature Study Society found a population near Vandalia, Illinois. The boldly black-spotted yellow caterpillars should be looked for in Missouri, too. The new species also feeds on the closely related Sampson's snakeroot (Orbexilum pedunculatum), which grows in the southern half of Missouri.
