Amorpha canescens Pursh

Lead Plant


CC = 8
CW = 5
MOC = 77

© DETenaglia

Family - Fabaceae/Faboideae

Habit - Small shrubs or subshrubs, from a knotty rootstock with a deep thick taproot.

Stems - Ascending to erect, to 70 cm, unbranched or sparsely branched, usually densely pubescent with short whitish to gray woolly hairs, rarely nearly glabrous, also sparsely and obscurely glandular.

Amorpha_canescens_stem2.jpg Stem and leaves.

© SRTurner

Leaves - Alternate, odd-pinnately compound, stipulate. Stipules linear, purplish, deciduous, to 3 mm long. Leaves with 29-41 leaflets, subsessile, the petiole 0.5-1.0 mm long, much shorter than the width of the lowest leaflet, the rachis 8-13 cm long, the petiole and rachis densely pubescent with short whitish to gray woolly hairs. Leaflets 9-17 mm long, 4-8 mm wide, ovate-oblong to elliptic, rounded to cordate at the base and with a stalk 0.5-1.0 mm long, rounded or abruptly short-tapered to a minute sharp point at the tip, the margins entire, both surfaces sparsely to more commonly densely pubescent with short whitish to gray woolly hairs, also inconspicuously gland-dotted.

Amorpha_canescens_leaf1.jpg Adaxial.

© DETenaglia

Amorpha_canescens_leaf2.jpg Abaxial.

© DETenaglia

Amorpha_canescens_leaflets.jpg Leaflets adaxial.

© SRTurner

Amorpha_canescens_leaflets2.jpg Leaflets abaxial.

© SRTurner

Inflorescences - Terminal and axillary racemes 8-17 cm long, commonly in clusters of 7-9, the flower stalks 0.8-1.2 mm long, the axes canescent.

Amorpha_canescens_inflorescence.jpg Inflorescence.

© DETenaglia

Amorpha_canescens_inflorescence2.jpg Inflorescence.

© SRTurner

Flowers - Calyces 5-lobed, the tube 1.5-2.0 mm long, the lobes 1.5-2.0 mm long. Corollas not papilionaceous, the single petal 4-5 mm long, 2.0-2.5 mm wide, obovate, folded around stamens and pistil, bluish purple. Stamens 10, exserted, the free portion of the filaments 4-5 mm long, the anthers 0.3-0.5 mm long, yellow. Ovary superior, 1.0-1.5 mm long, densely hairy, the style 2-3 mm long, glabrous or densely hairy. Stigma glabrous, 3-lobed, purplish.

Amorpha_canescens_flowers.jpg Flowers.

© DETenaglia

Fruits - Modified legumes 3-4 mm long, 1.2-1.5 mm wide, slightly flattened, exserted beyond the persistent calyx tube, hairy and gland-dotted, 1-seeded. Seeds 2.0-2.4 mm long, 1.0-1.4 mm wide, olive to reddish brown.

Amorpha_canescens_fruits.jpg Fruits.

© SRTurner

Flowering - May - August.

Habitat - Upland prairies, loess hill prairies, glades, tops of bluffs, savannas, and openings of dry upland forests, pastures, railroads, roadsides. Also cultivated.

Origin - Native to the U.S.

Lookalikes - Tephrosia virginiana, when not in flower.

Other info. - This species of Amorpha is easily recognized when flowering by its dense canescence (conspicuous gray hairiness) and distinctive inflorescences. Non-flowering specimens can appear similar to another legume, Tephrosia virginiana (goat's rue). The two can be reliable distinguished by the shape of the leaflet bases: in A. canescens these are rounded or slightly cordate, whereas in T. virginiana they are tapered. The presence or absence of a mucro (minute spiny tip) on the leaflets is less reliable.

The plant is found throughout most of Missouri and the Midwest. The species has been subdivided based on pubescence characters, but in Missouri these intergrade and are not formally recognized. The flowers are protogynous, with the style maturing before the stamens. The fruits are small, reaching a length of 4 mm. The species is also edible. A. canescens was once thought to signal the presence of lead ore. It does well in the garden and is often cultivated for its attractive floral display and gray foliage and stems.

Photographs taken at Lichen Glade, St. Clair County, MO., 6-16-05 and at Indigo Prairie Conservation Area, Dade County, MO., 6-18-05 (DETenaglia); also at St. Joe State Park, St. Francois County, MO, 5-14-2012, and Little Lost Creek Conservation Area, Warren County, MO, 6-9-2017 and 7-7-2020 (SRTurner).