Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald

Illinois Bundle Flower


CC = 3
CW = 3
MOC = 68

© SRTurner

Family - Fabaceae/Mimosoideae

Habit - Perennial forb with a thickened, woody taproot.

Stems - Ascending to erect, to 1.2 m, multiple from base, much branched, often ridged, glabrous or with a few sparse hairs on ridges above, green when young, becoming reddish brown with age (mostly near the base).

Desmanthus_illinoensis_stem.jpg Stem and node.

© SRTurner

Leaves - Alternate, bipinnately compound, short-petiolate, stipulate. Petioles 0.2-0.5 cm long, the petiole and rachis glabrous or hairy, with a lozenge-shaped gland between the lowermost pair of leaflets, occasionally also between a few of the other leaflet pairs. Stipules inconspicuous, linear to hairlike, 4-9 mm long, with a small, winglike, expanded base. Blades mostly 5.0-8.0 cm long, with 6-12 pairs of pinnae, each pinna with 15-30 pairs of leaflets, usually an even number. Leaflets small, 1.5-4.0 mm long, 0.5-0.8 mm wide, narrowly oblong to linear, oblique at the base, angled or short-tapered to a sharply pointed tip, glabrous or with sparse ascending hairs along the margins.

Desmanthus_illinoensis_leaves.jpg Leaves.

© SRTurner

Desmanthus_illinoensis_leaf.jpg Leaf.

© DETenaglia

Desmanthus_illinoensis_leaflets1.jpg Leaflets adaxial.

© SRTurner

Desmanthus_illinoensis_leaflets2.jpg Leaflets abaxial.

© SRTurner

Inflorescences - Axillary globose pedunculate cluster of 20-70 sessile flowers, 1.0-1.2 cm in diameter. Peduncle 1-4 cm, in flower, elongating in fruit to 3-6 cm, antrorse strigose.

Desmanthus_illinoensis_inflorescences.jpg Inflorescences.

© SRTurner

Desmanthus_illinoensis_inflorescence.jpg Inflorescence.

© SRTurner

Flowers - Mostly perfect, with a few staminate and/or sterile flowers often produced, these usually smaller than the perfect ones. Calyces 1.4-2.0 mm long (as short as 0.6 mm in sterile flowers), 5-lobed, glabrous, the tube white. Corollas of 5 petals, 2.0-3.3 mm long. Stamens 5, white, glabrous, exserted, the filaments 4-6 mm long. Anthers yellow, 0.2-0.3mm in diameter. Ovary 1 mm long, greenish-white, glabrous. Style 4 mm long, white, glabrous, well exserted.

Fruits - Borne in contorted globose clusters. Individual legumes 1-2 cm long, 5-7 mm wide, asymmetrically oblong, slightly curved to strongly twisted, obliquely rounded at the base, strongly flattened, tapered to a sharply pointed tip, the margins not or only occasionally indented between the seeds, the surfaces not constricted between the seeds, reddish brown to black at maturity, dehiscent along both sutures but more slowly on one side than the other, with 2-5 seeds. Seeds 3-4 mm long, 2.0-2.5 mm wide, obovate to somewhat rhombic in outline.

Desmanthus_illinoensis_fruits.jpg Immature fruits.

© DETenaglia

Desmanthus_illinoensis_fruits1.jpg Immature fruits.

© SRTurner

Desmanthus_illinoensis_fruits2.jpg Mature fruits dehiscing.

© SRTurner

Flowering - June - August.

Habitat - Glades, upland prairies, upland forests, savannas, streambanks, pond margins, fencerows, pastures, fields, railroads, roadsides, open disturbed areas.

Origin - Native to the U.S.

Lookalikes - Acacia angustissima

Other info. - This species can be found throughout most of Missouri, less commonly in the northeast corner of the state and the central Ozark region. Beyond Missouri the plant's main range is within the central and central-south continental U.S. The plant can be identified by its small, globose clusters of white flowers and its bipinnate leaves. Residents of the extreme southwestern portion of Missouri might mistake this plant for Acacia angustissima, except that the latter has many more stamens per flower, giving the flowers clusters a much more dense appearance. A. angustissima also has very dark reddish-brown, woody stems and no glands on the leaf petioles.

Though it has a somewhat weedy appearance, Illinois bundleflower is one of the most important of our native prairie legumes. It is a nutritious plant which is readily consumed by livestock, deer, and antelope, and it has been studied as a potential human grain crop. Because it decreases under heavy grazing, it is an indicator species for range condition. The seeds are eaten by birds and small mammals. Native Americans used the plant in medicine, and as a source of ceremonial rattles for children.

Photographs taken off Interstate 24 near Nashville, TN., 8-3-05 (DETenaglia); also at Shaw Nature Reserve, Franklin County, MO, 7-24-2007, near Pacific Palisades Conservation Area, MO, 7-22-2015, Gray Summit, Franklin County, MO, 6-25-2017, along the Katy Trail near Treloar, Warren County, MO, 7-24-2019, and Marais Temps Clair Conservation Area, St. Charles County, MO, 7-5-2020 (SRTurner).