Aeschynomene rudis Benth.

Rough Jointvetch

Aeschynomene rudis plant

Family - Fabaceae/Faboideae

Habit - Robust annual forb.

Stem - Ascending to erect, to 2 m, sometimes branched, the upper portion moderately pubescent with pustular-based spreading hairs to 2 mm long.

Aeschynomene_rudis_stem.jpgStem and stipule.

Leaves - Alternate, pinnately even-compound, petiolate, sensitive to light and touch. Stipules conspicuous on young growth but usually shed with age, herbaceous, lanceolate, peltate, with a small lobelike appendage below the point of attachment, 8-10 mm long, 4-5 mm wide, tapered to a sharply pointed tip. Petioles 10-12 mm long, the rachis 9-12 cm long, the petiole and rachis pubescent with pustular-based nonglandular, whitish hairs. Blades with 40-50 leaflets, these subopposite, 8-16 mm long, 2-3 mm wide.

Aeschynomene_rudis_leaf1.jpgLeaf adaxial.

Aeschynomene_rudis_leaf2.jpgLeaf abaxial.

Aeschynomene_rudis_leaf2b.jpgLeaf after being touched.

Flower - Peduncles often glandular-hairy and sticky, the bracts subtending the flowers similar to the stipules but often smaller. Calyces with the tube 0.8-1.0 mm long; the upper lip 4-5 mm long, shallowly 2-lobed apically; the lower lip 4-5 mm long, shallowly 3-lobed apically. Corollas papilionaceous, glabrous, yellow to orange, sometimes striped or tinged with red or purple, the petals tapered to a short stalklike base; the banner broadly ovate to nearly circular; the wings narrowly obovate; the keel oblanceolate and curved in outline, boat-shaped. Stamens 10, the filaments all fused, the tube split on 1 side or more commonly deeply on 2 sides into 2 groups of 5 stamens each, the anthers small, attached near the midpoint, all similar in size. Ovary linear, short-stalked, often hairy, the style glabrous, curved, the stigma small and terminal.


Fruits - Fruits 4-6 cm long, 4-6 mm wide, the stalk 4-6 mm long, the surfaces at maturity sparsely pustular- hairy, usually with pronounced medial lines of stout pustular-based, warty projections to 1 mm long, dehiscent into 7-12 segments, these 5-6 mm long, 5-6 mm wide. Seeds 4-5 mm long, 2-3 mm wide, reddish brown to olive brown.


Aeschynomene_rudis_fruits2.jpgFruits with prominent warts.

Flowering - July - September.

Habitat - Fields, ditches, rice paddies.

Origin - Native to South America.

Lookalikes - Aeschynomene indica.

Other info. - This introduced legume was first reported in Missouri in 1994, and remains rare in the state. Its U.S. range is sparse, consisting principally of widely scattered locations in a few southern states. The plant is somewhat weedy and, since it prefers seasonally flooded areas such as marshes and rice paddies, has the potential to become a problem in rice fields.

This species strongly resembles the closely related A. indica, and differentiation from that species can be difficult. Numerous distinguishing characters have been published but many of these are controversial. Yatskievych lists the prominent warty projections on the fruit as a principal identifying attribute of A. rudis, and these are clearly shown in the photo above.

Photographs taken at Otter Slough Conservation Area, Stoddard County, MO, 9-11-2019 (SRTurner).