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Amorpha schwerinii Schneid.
Piedmont Indigo-bush
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G3G4
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: High Conservation Concern
Element Occurrences (EOs) in Georgia: 8
Habitat Summary for element in Georgia: Rocky upland woods
Perennial, deciduous shrub with widely spreading branches and stems 3 - 10 feet (1 - 3 m) tall, covered with short hairs and a few scattered amber-colored glands. The leaves are alternate and compound, 2 - 8 inches (5 - 20 cm) long, widely spreading, with 7 - 29 leaflets. Leaflets are 0.4 - 1.6 inch (1 - 4 cm) long, usually oblong to elliptic; the upper leaflet surfaces are covered with very short hairs, the lower surfaces are densely hairy, and both sides have glandular dots; the veins are slightly elevated above the surface of the leaflet, and the midvein of each leaflet extends beyond the tip into a glandular knob; leaflet margins are usually entire and flat (not inrolled). Flower clusters are held erect at the top of the stem with one or occasionally 2 or 3 spike-like racemes up to 6 inches (15 cm) long. Flowers consist of a hairy, reddish-green, 5-lobed calyx with raised glands; a single dark purple petal; and 10 long, golden or purple, orange-tipped stamens extending beyond the petal. Fruits are oblong, usually hairy, one-seeded pods about 0.25 inch (0.5-0.7 cm) long, with raised glands on the upper half of the pod.
Indigo-bush (Amorpha fruticosa) is a common shrub, 3 - 12 feet (1 - 4 m) tall, occurring statewide on riverbanks and marshy shores, and in forests, woodlands, and disturbed sites. Its leaves and stems are slightly to very hairy. Its leaves have 9 - 23 leaflets, and the midvein of the leaflet extends into a pointed or swollen tip. Its calyxes are covered with small, bulging glands, and the flower is purple.
Appalachian Indigo-bush (Amorpha glabra) occurs in dry ridgeline and slope forests in the Blue Ridge, upper eastern Piedmont, and Coastal Plain in Georgia. It is 3 - 6 feet tall, with hairless stems and leaves. Its leaves have 9-19 leaflets, often bearing a slightly enlarged, gland-like tip; the margins are not inrolled. Its flowers are purple.
Dwarf Indigo-bush (Amorpha herbacea var. herbacea) has conspicuously hairy stems, leaves, calyxes, and (usually) fruits. Its leaves have 21 - 45 leaflets with inrolled margins and round, glandular knobs at the tips. Its flowers are white or purple.
Georgia Indigo Bush (Amorpha georgiana) occurs in pine flatwoods and on sandy stream terraces in the Coastal Plain. It is less than 3 feet (1 m) tall, and its stems and leaves are hairless or nearly so. Its leaves have 13-39 leaflets, each tipped with a tiny, sharp point that is sometimes capped with a round gland. Its flowers are purple or blue, and its fruits are not hairy.
Florida Lead-bush (Amorpha herbacea var. floridana) occurs on sandy stream terraces and in pine flatwoods in the Coastal Plain. It is 1.3-5 feet (0.4-1.5 meters) tall and has mostly hairless stems, leaves, and fruits. Its leaves have 21-45 leaflets, each tipped with a tiny, round, glandular knob; the leaflet margins are rolled under. Its flowers are purple, and the fruits are hairless.
Shining Indigo-bush (Amorpha nitens) occurs on rocky, wooded slopes and in alluvial forests in several counties throughout Georgia (except for Blue Ridge counties). It is 3-6 feet (1-2 meters) tall with hairy stems and leaves. Its leaves have 7-19 lustrous leaflets that usually have an extended, tapering midvein tip and flat (not inrolled) margins. Its flowers are purple, and the fruits are not hairy.
In Georgia, Schwerin's Indigo-bush is found on and around granite flatrocks and monadnocks. In other states, it occurs in dry, rocky forests and woodlands and also in alluvial forests.
There is little to no published information about the life history of Schwerin's Indigo-bush. Common Indigo-bush (Amorpha fruticosa), a close relative, is pollinated by bees seeking both pollen and nectar from the flowers, including Andrena quintilis, a specialist pollinator of Amorpha species. The caterpillars of Gray Hairstreak, Silver-spotted Skipper, and Southern Dogface butterflies, as well as those of Black-spotted Prominent moths, use Common Indigo-bush leaves as food; it is possible they also use other species of Amorpha as host plants. As with most species in the legume family (Fabaceae), nitrogen-fixing bacteria live in nodules on the roots of all Amorpha species. Birds have been seen opening the fruits and eating the seeds. Zasada and Martineau (2008) describe the collection, storage, and planting of seeds from Amorpha species.
Schwerin's Indigo-bush flowers April–June and fruits June–October. Since it is distinguished from similar species largely on the basis of leaf and stem traits, it may be identified throughout the growing season.
Schwerin's Indigo-bush is found almost entirely in the Southeastern Piedmont ecoregion of Georgia, South Carolina, North Carolina, and Alabama; it also occurs in northeastern Mississippi.
Populations that occur around granite outcrops have been destroyed by quarrying and are also threatened by trampling and recreational vehicle use. Plants in forest and woodland habitats are threatened by clearcut logging, pine plantations, commercial and residential development, and fire suppression.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Residential & commercial development | Climate change & severe weather | None |
| Specific Threat | None | None | None |
Amorpha schwerinii is ranked S2 by the Georgia Department of Natural Resources, indicating that it is imperiled in the state. It has been documented at 7 sites in 6 counties since 1929; one of these populations was destroyed by quarrying, and most have not been confirmed in many years – their current status is unknown. One population in Stone Mountain Park is protected.
Schwerin's Indigo-bush benefits from natural disturbance that increases sunlight, such as fire and wind throw, and human disturbance, such as selective tree removal. Protect granite outcrops from recreational vehicle use, trash dumping, and other human disturbances.
GADNR. 2019. Element occurrence records for Amorpha schwerinii. Georgia Department of Natural Resources, Wildlife Resources Division. Social Circle, Georgia.
Hilty, J. 2019. Species account for Amorpha fruticosa. Illinois Wildflowers. Accessed 3 July 2019. https://www.illinoiswildflowers.info/trees/plants/false_indigo.htm
Isley, D. 1990. Leguminosae (Fabaceae), volume 3, part 2, Vascular flora of the southeastern United States. University of North Carolina Press, Chapel Hill.
NatureServe. 2019. Species account for Amorpha schwerinii. NatureServe Explorer: an online encyclopedia of life, Version 7.1. NatureServe, Arlington, Virginia. Accessed 8 June 2019. http://explorer.natureserve.org/servlet/NatureServe?searchName=Amorpha+schwerinii
Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill.
Wilbur, R.L. 1975. A revision of the North American genus Amorpha (Leguminosae-Psoraleae). Rhodora 77(811): 337-409. Accessed 5 July 2019. https://www.jstor.org/stable/23311397?seq=1#metadata_info_tab_contents
Zasada, J.C. and D. Martineau. 2008. Amorpha L. – amorpha, indigobush. In, F.T. Bonner and R.P. Karrfalt, eds. “Woody Plant Seed Manual,” pages 250-254. U.S. Department of Agriculture, Forest Service, Agriculture Handbook 727. Accessed 5 July 2019. https://www.fs.usda.gov/nsl/Wpsm%202008/A%20genera.pdf
Linda G. Chafin
Linda G. Chafin, 5 July 2019: original account