Amorpha canescens Pursh

Lead Plant

Amorpha canescens plant

Family - Fabaceae

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

Stems - To 1m tall, ascending to erect, woody below, multiple from base, typically simple, canescent above, sparsely pubescent to glabrescent below, striate-nerved.

Amorpha canescens stem2Stem and leaves.

Leaves - Alternate, odd-pinnately compound, stipulate. Stipules linear, purplish, deciduous, to 3 mm long. Leaves to 8 cm long, the rachis canescent. Leaflets alternate to opposite, stipellate. Stipels small, purple, thin and dry. Leaflets entire, typically linear-oblong to lanceolate-ovate, mucronate, rounded at the base, with single midrib, canescent, to 1.6 cm long, 5 mm broad. Terminal leaflet smaller than laterals, cuneate at base, truncate at apex, mucronate.

Amorpha canescens leafAdaxial. Amorpha canescens leafAbaxial.

Amorpha canescens leafletsLeaflets adaxial.

Amorpha canescens leaflets2Leaflets abaxial.

Inflorescence - Multiple terminal and axillary racemes, indeterminate, pedunculate, to 25 cm long, near stem tips. Axis of racemes canescent. Pedicels to 1 mm long.

Amorpha canescens inflorescenceInflorescence.

Amorpha canescens inflorescence2

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 flowersFlowers.

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.

Flowering - May - August.

Habitat - Upland prairies, glades, forest openings, bluffs, roadsides. Also cultivated.

Origin - Native to U.S.

Other info. - This species of Amorpha is easily recognized when flowering by its dense canescence (conspicuous gray hairiness). 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 (SRTurner).


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