Desmodium rotundifolium DC.



CC = 6
CW = 5
MOC = 46

© SRTurner

Family - Fabaceae/Faboideae

Habit - Perennial forb with a short, often woody rootstock and often a taproot.

Stems - Prostrate, to 1.5 m, branched, the median portion moderately pubescent with straight, spreading hairs, sometimes also with sparse to moderate, hooked hairs.

Desmodium_rotundifolium_stem.jpg Stem and stipules.

© SRTurner

Leaves - Alternate, trifoliate, petiolate, stipulate. Petioles of the median leaves 1-5 cm long, somewhat reduced toward the stem tip. Stipules 5-12 mm long, 3-5 mm wide, ovate (the base partially clasping the stem), tapered to a sharply pointed tip, at maturity brown and spreading to more commonly reflexed, persistent. Leaflets flat or nearly so, the undersurface with straight, spreading hairs, the network of raised veins inconspicuous to evident. Central leaflet 2-7 cm long, 2-6 cm wide, often slightly larger than the lateral pair, more or less circular to broadly ovate, broadly obovate, or somewhat rhombic, the tip mostly rounded. Lateral leaflets 2-4 cm long 2-4 cm wide. Stipels 1-3 mm long.

Desmodium_rotundifolium_leaves.jpg Leaves.

© SRTurner

Desmodium_rotundifolium_leaf1.jpg Leaf.

© SRTurner

Desmodium_rotundifolium_leaflet1a.jpg Leaf adaxial surface.

© SRTurner

Desmodium_rotundifolium_leaflet2.jpg Leaflet abaxial.

© SRTurner

Desmodium_rotundifolium_leaflet2a.jpg Leaflet abaxial surface.

© SRTurner

Inflorescences - Terminal and axillary loose racemes and panicles in the apical 1/3 of the stems, often unbranched, the axis with straight, spreading and hooked hairs. Stipules somewhat reduced in inflorescence. Primary bracts 4-6 mm long, ovate, tapered to a sharply pointed tip, mostly persistent. Secondary bracts 1.0-1.2 mm long, linear to hairlike, sometimes shed early. Flower stalks 6-22 mm long.

Desmodium_rotundifolium_inflorescence.jpg Inflorescence.

© SRTurner

Desmodium_rotundifolium_inflorescence2.jpg Inflorescence.

© SRTurner

Flowers - Calyces green, densely pubescent with minute hairs and with sparse, long, straight, spreading hairs, especially on the lower lip, the tube 1.7-2.0 mm long, the lobes 2-3 mm long, triangular-acuminate, mostly equal. Corollas papilionaceous, 7-12 mm long, pink or rarely white, the nectar guides yellow and white outlined in purple. Standard 1 cm broad. Keels and wings to 9 mm long, glabrous. Keels connate. Wings connate basally to keels. Stamens diadelphous. Anthers greenish-yellow, 0.3-0.4 mm long. Ovary green, puberulent, 3-4 mm long. Style upcurved, 1.5 mm long, glabrous, green.

Desmodium_rotundifolium_flower1.jpg Flower.

© DETenaglia

Desmodium_rotundifolium_flower2.jpg Flower.

© SRTurner

Desmodium_rotundifolium_flower4.jpg Flower and calyx.

© SRTurner

Desmodium_rotundifolium_flower3.jpg Flower from rear.

© SRTurner

Fruits - Loments, straight in outline, the stalklike base 3-5 mm long, consisting of 3-6 segments, each 5-7 mm long and 3-5 mm wide, angled or more or less rounded on the upper margin, angled on the lower margin, with deeper indentations below, less commonly rounded and nearly equally indented above and below, with dense hooked hairs on the margins and scattered hooked hairs on the faces.

Flowering - July - September.

Habitat - Mesic upland forests, sand savannas, margins of glades, ledges and tops of bluffs, railroads, roadsides. Usually in acid soils.

Origin - Native to the U.S.

Lookalikes - None.

Other info. - This distinctive species occurs in the southeastern half of Missouri, and in somewhat scattered fashion across much of the eastern half of the continental U.S. It is easily recognized even vegetatively by its prostrate habit and trifoliate leaves with round leaflets. It is most often found in areas of acidic soil.

Another prostrate species of tick trefoil is D. ochroleucum M. A. Curtis. The terminal leaflets of this species are not entirely rotund, the flowers are usually white, and the fruits are often twisted between the segments. This species is very rare in Missouri.

Photographs taken in Big Spring State Park, 8-20-03 (DETenaglia); also near Loda Lake, Newaygo County, MI, 8-29-2020, and at Don Robinson State Park, Jefferson County, MO, 9-16-2021 (SRTurner).