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Nabalus barbatus (Torrey & A. Gray) A. Heller
Barbed Rattlesnake-root
Federal Protection: No US federal protection
State Protection: Rare
Global Rank: G3
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): No
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: High Conservation Concern
Element Occurrences (EOs) in Georgia: 15
Habitat Summary for element in Georgia: Limestone glades and barrens, edges of remnant prairies
Prenanthes barbata (synonym Nabalus barbatus) is a perennial herb with milky latex in stems and leaves. Its stems are 1.6 - 5 feet (50 - 150 cm) tall, erect, repeatedly branched above the middle, smooth or hairy, and reddish-purple. The leaves are 1.6 - 4 inches (4 - 10 cm) long and 0.4 - 1.6 inches (1 - 4 cm) wide, reduced in size upward on the stem, alternate, leathery, smooth or hairless; mid-stem leaves are sometimes shallowly lobed or toothed and taper to a winged leaf stalk; upper leaves are irregularly, shallowly toothed and clasping the stem; lowest leaves are withered by flowering time. Flower heads droop at the tips of branchlets in much branched clusters. The base of each flower head is surrounded by a cylindrical involucre 0.5 - 0.7 inch (1.2 - 1.7 cm) long consisting of 6 - 10 narrow, dark reddish-purple (sometimes dark green) bracts covered with stiff, white or purple, spreading hairs. Ray flowers are up to 15 in number, white or cream-colored, with finely toothed tips and long, showy stigmas with curling tips; there are no disk flowers. Fruits are about 0.4 inch (8-10 mm) long, dry, seed-like, with barbed bristles at the base.
Tall Rattlesnake-root (Nabalus altissimus, synonym Prenanthes altissima) leaves are usually deeply lobed, and its flower heads have 4 - 7 greenish-yellow ray flowers and 6 or fewer bracts in the involucre. The involucral bracts are pale green and usually hairless or have only a few hairs at the tip.
Lion’s Foot (Nabalus serpentarius, synonym Prenanthes serpentaria) leaves are deply lobed or divided nearly to the midvein. Its involucral bracts are green or purple, with only a few stiff hairs, and its ray flowers are pale yellow.
Gall-of-the-earth (Nabalus trifoliolatus, synonym Prenanthes trifoliatus) leaves are highly variable, oval to triangular and coarsely and deeply toothed or lobed; its stem is also purple and the involucral bracts are green or purple and smooth or only slightly hairy.
None in Georgia.
Coosa Valley prairies, calcareous flatwoods and hardwood bottomlands, edges of limestone glades, and roadsides and rights-of-way through these habitats.
Prenanthes barbata is a perennial herb that reproduces sexually by seed but, unfortunately, these plants seldom flower or set fruit due to canopy closure. Its flowers are probably pollinated by bees seeking nectar or possibly by the wind when grown in open habitats, although no studies have been conducted to confirm this. The barbed bristles that surround the base of each fruit stick to the fur of animals and promote seed dispersal. The milky sap in leaves and stems is bitter which discourages insect predation.
Surveys are best conducted during flowering (early September–late October) because flowers are required for positive identification; unfortunately, plants seldom flower due to canopy closure at most sites. Without flowers, look for a combination of these traits: habit with calcareous soils, reddish-purple stems, and lowest leaves with coarsely dentate or serrate (but not lobed) margins.
Georgia, Alabama, Mississippi, Louisiana, Texas, Arkansas, and Kentucky.
Conversion of habitat to pine plantations, agriculture, and residential and commercial development; canopy closure; off-road vehicle use; invasion by exotic pest plants.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Biological resource use | Human intrusions & disturbance | Natural system modifications |
| Specific Threat | None | None | None |
Prenanthes barbata is ranked S2 by the Georgia Department of Natural Resources, indicating that it is imperiled in Georgia. Fourteen small populations are known in Georgia; seven are protected by conservation easement, and three occur on a college campus.
Use prescribed fire or hand-clearing to create sunny openings and encourage flowering. Avoid clearing, bedding, and other mechanical disturbances. Exclude vehicles from prairies and limestone glades. Eradicate exotic pest plants.
Bogler, D.J. 2006. Prenanthes barbata species account. Flora of North America, vol. 19. Oxford University Press, New York. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250067367
Chafin, L.G. 2007. Field guide to the rare plants of Georgia. State Botanical Garden of Georgia and University of Georgia Press, Athens.
Cronquist, A. 1980. Vascular flora of the southeastern United States, vol. 1, Asteraceae. University of North Carolina Press, Chapel Hill.
GADNR. 2020. Element occurrence records for Prenanthes barbata. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, Georgia.
Horn, D., T. Cathcart, T.E. Hemmerly, and D. Duhl. 2005. Wildflowers of Tennessee, the Ohio Valley, and the southern Appalachians. Lone Pine Publishing, Auburn, Washington.
NatureServe. 2019. Prenanthes barbata comprehensive report. NatureServe Explorer. Arlington, Virginia. http://explorer.natureserve.org/servlet/NatureServe?searchName= Prenanthes+barbata
Singhurst, J.R., R.J. O'Kennon, and W.C. Holmes. 2004. The genus Prenanthes (Asteraceae: Lactuceae) in Texas. Sida 21(1): 181-191. https://www.jstor.org/stable/41968991?seq=1#metadata_info_tab_contents
Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill. http://www.herbarium.unc.edu/flora.htm
Linda G. Chafin
L. Chafin, Jul. 2008: original account
K. Owers, Feb. 2010: added pictures
L. Chafin, Mar. 2020: updated original account
