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Arabis georgiana Harper
Georgia Rockcress
Federal Protection: Listed Threatened
State Protection: Threatened
Global Rank: G1
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): Yes
Element Occurrences (EOs) in Georgia: 11
Habitat Summary for element in Georgia: Rocky or sandy river bluffs and banks, in circumneutral soil
Perennial herb with unbranched stems up to 3 feet (90 cm) tall; upper stem is smooth, lower stem is hairy. Basal leaves 1.5 - 3 inches (4 - 8 cm) long, widest above the middle, with toothed margins, bluntly pointed tips, and bases tapering to a leaf stalk. Stem leaves 0.4 - 2 inches (1 - 5 cm) long, larger near the base of the stem, decreasing in size upward; coarsely toothed, lightly hairy on the lower surface, slightly clasping at the base but with no leaf stalks. Flowers are about 0.4 inch (1 cm) long with 4 white petals, held in a loosely branched cluster at the top of the stem. Fruit is a very narrow, straight pod, 2 - 2.75 inches (5 - 7 cm) long, held erect, splitting lengthwise, with 20 - 30 brown, slightly winged seeds.
Canada Rockcress (Boechera canadensis, synonym: Arabis canadensis) also occurs in rocky habitats, including Georgia Rockcress sites. It usually lacks basal leaves, and its stem leaves are not clasping. Its fruits are curved and drooping.
Smooth Rockcress (Boechera laevigata, synonym: Arabis laevigata) also occurs in rocky habitats, including Georgia Rockcress sites. It has hairless, pale bluish-green stems and leaves. Its fruits are curved and are spreading or drooping, not held erect.
Missouri Rockcress (Boechera missouriensis, synonym: Arabis missouriensis) has dark green (not pale bluish-green) stems, and narrow, toothed, overlapping stem leaves that do not clasp the stem. Its fruits are erect at first, then later arch outwards. It occurs on Piedmont granite outcrops. For more information, see: https://georgiabiodiversity.org/portal/profile?group=plants&es_id=17367
Shallow, basic or circumneutral soils on rocky slopes and bluffs above streams; sandy loam along eroding riverbanks; thin woods on limestone or granite bluffs. Although it is occasionally found in adjacent moist forests or woodlands, Arabis georgiana will not persist in heavily shaded conditions. It requires high to moderate light conditions, and occurs on soils that have a circumneutral to slightly basic pH. It often occurs with Eastern Red Cedar, Black Oak, Sugar Maple, Chestnut Oak, and Oakleaf Hydrangea.
Georgia Rockcress is a perennial herb that reproduces sexually by seed. Although it will persist in shady habitats, it flowers and fruits best when exposed to sun for most of the day. It appears to depend exclusively on sexual reproduction and is probably not self-compatible since the female stigma in a given flower becomes receptive before that flower’s pollen is released. Seeds have been observed to germinate in the fall and winter of the year they are produced. Georgia Rockcress is not a strong competitor and grows where many other plants are excluded by thin, rocky soils or recent soil erosion.
Surveys are best conducted during fruiting (May–early July), when fruit length and orientation are apparent. Plants flower March–April but its flowers resemble those of other Arabis and Boechera species.
Arabis georgiana occurs in 7 counties in Georgia and 8 counties in Alabama.
Habitat loss and fragmentation from stream impoundment, road and bridge building, and timber harvesting, mining, and commercial and residential development. Invasion by exotic pest plants such as Japanese Honeysuckle (Lonicera japonica).
Arabis georgiana is listed as Threatened by the state of Georgia and by the U.S. Fish and Wildlife Service. It is ranked S1 by the Georgia Department of Natural Resources, indicating that it is imperiled in the state. Eleven populations have been documented in Georgia over the last century or so, but only 8 are currently known.
Establish buffer zones around known sites and protect them from disturbances such as logging, mining, road- and bridge-building. Re-route trails and roads that encroach on populations. Develop management plans for all sites on public and private conservation lands. Eradicate exotic pest plant species such as Japanese honeysuckle (Lonicera japonica) at known sites and monitor annually for re-infestation. Research and address causes of low reproductive success in this species.
Al-Shehbaz, I.A. 1988. The genera of Arabideae (Cruciferae; Brassicaceae) in the southeastern United States. Journal of the Arnold Arboretum 69(2): 85-166. https://www.jstor.org/stable/43797836?seq=1#metadata_info_tab_contents
Al-Shehbaz, I.A. 2003. Transfer of most North American species of Arabis to Boechera (Brassicaceae). Novon 13: 381 - 391. https://www.jstor.org/stable/3393366?seq=1#metadata_info_tab_contents
Chafin, L.G. 2007. Field guide to the rare plants of Georgia. State Botanical Garden of Georgia and University of Georgia Press, Athens.
GADNR. 2019. Element occurrence records for Arabis georgiana. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, Georgia.
Garcia, A.M. 2012. Demographic and genetic consequences of small population size in remnant populations of Arabis georgiana Harper (Georgia Rockcress). M.S. Thesis, Columbus State University, Columbus, Georgia. https://csuepress.columbusstate.edu/theses_dissertations/31/
Harper, R.M. 1903. A new Arabis from Georgia. Torreya 3: 87-88. https://www.jstor.org/stable/40594189?seq=1#metadata_info_tab_contents
NatureServe. 2019. Arabis georgiana comprehensive report. NatureServe Explorer. Arlington, Virginia. http://explorer.natureserve.org/servlet/NatureServe?searchName=Arabis+georgiana
Patrick, T.S., J.R. Allison, and G.A. Krakow. 1995. Protected plants of Georgia. Georgia Department of Natural Resources, Natural Heritage Program, Social Circle.
USFWS. 1995. Status survey of Arabis georgiana (Georgia Rockcress) in Georgia. U.S. Fish and Wildlife Service, Jackson, Mississippi.
USFWS. 2019. Arabis georgiana (Georgia Rockcress) species profile and related documents. U.S. Fish and Wildlife Service. https://ecos.fws.gov/ecp0/profile/speciesProfile?sId=4535
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, Sept. 2007: original account.
K. Owers, Jan. 2010: updated status and ranks, added pictures.
Z. Abouhamdan, April 2016: updated link.
L. Chafin, Jan 2020: updated original account..
