For over a century, the watershed of the Cahaba River (above, left) in Bibb County, Alabama has been known to contain a considerable number of rare plants. Among these are

 Botanical explorations since 1992 have revealed that Bibb County is blessed with an even greater number of rarities than anyone had imagined. It appears, in fact, to support the most significant diversity of rare plant species of any county in the temperate Southeast!

Most important was the discovery of eight different plants that were previously unknown to science. These were given the vernacular names of Cahaba paintbrush, Ketona tickseed, Cahaba prairie-clover, Cahaba daisy fleabane,  Cahaba torch,  deceptive marbleseed,  sticky rosinweed, and Alabama gentian pinkroot.

These explorations have revealed eight other species that had never before been reported from Alabama. These included Thorne's beakrush, a former  national Candidate Species known  previously from a handful of sites in Georgia, Florida, and North Carolina; Virginia nailwort, previously unknown in the territory between Arkansas and Virginia; star-scale cloak fern, disjunct from Texas; shining ladies'-tresses, thought to range only as far south as Tennessee, where it is quite rare;

wiry beakrush, previously known as far south as Tennessee (until found in Texas in 1989); and blue wild-indigo. An even more noteworthy addition to the flora of Alabama was a plant that had been presumed extinct, dwarf horse-nettle. Its existence anywhere had not been confirmed since the 1830's(!), when it was twice found in Georgia. Also new to Alabama was a lichen, called bordered scale in Lichens of North America; previous collections had come from no closer than Arkansas.

Bibb County is now thought to support more populations than any other county, anywhere, of two plant species listed under the national Endangered Species Act. Besides Mohr's Barbara's-buttons, are seven newly discovered populations of Tennessee yellow-eyed grass, a plant that had previously been known in Alabama only from one small population about 100 miles to the northwest. Besides Georgia rockcress, several populations were found of another Candidate for listing, Georgia aster.

Among other discoveries were ten locations for jamesianthus, a former Candidate Species that had been assumed previously to be restricted to a tiny area in Alabama more than 110 miles to the northwest. Royal catchfly was known only historically in Alabama, from Bibb County and a few Black Belt counties. It had been feared extinct in the state but is now known from about a dozen places in Bibb County.

In addition to all of these ultra-rarities are about two dozen other plants considered rare by the Alabama Natural Heritage Program and only recently found to grow in Bibb County (Alabama snow-wreath, Allegheny spurge, barrens aster, Butler's quillwort, croomia, culver's root, decumbent toadshade, eastern wahoo, heart-leaved plantain, Great Plains ladies'-tresses, 

limestone adder's-tongue fern, Nashville breadroot, one-flowered cancer-root, Ozark bunchflower, prickly-ash, purple coneflower, shadow-witch, small-flowered phacelia, Smith's sunflower, 

sunnybells, wide-leaved bunchflower, white four-o'clock, widespread gladecress, and yellow least gladecress). Another rarity, Catesby's bindweed, appears to have been overlooked by the ALNHP and should be added to their list of Alabama rare plants. All totaled, Bibb County contains at least 76 rare species of vascular plants, an incredibly high number! Why Bibb County should be blessed with such a bonanza of botanical rarities is not fully understood. There are, however, several factors that surely have contributed to its tremendous biological diversity.

One factor is the considerable variety of geological formations found in the county. Three geographic regions, each with a distinctive assortment of plants and animals, intersect there: the Upper Coastal Plain, the Cumberland Plateau, and the Ridge and Valley. A second factor is the mostly rural character of the county, with much intact habitat for wildlife. A third factor is the presence of multiple outcrops of a most unusual kind of rock.

Fully half of the rare plant species of Bibb County are found principally on or near open, mostly treeless, glades that have developed over an ancient (upper Cambrian) rock formation known as the Ketona Dolomite. Dolomite is a sedimentary rock composed chiefly of the carbonates of calcium and magnesium. There are several other kinds of dolomite found in Alabama and the other southeastern states, but they typically have considerable impurities, especially siliceous materials such as chert. It is not unusual for chert to form 40% of such rocks. Ketona Dolomite, by contrast, is unusually pure, with only about 2% impurities. This has important consequences for the development of plant life where this rock is exposed.

Because its magnesium carbonate is not significantly diluted by chert or other impurities, the soil derived from the weathering of Ketona Dolomite is exceptionally high in magnesium. Magnesium is an element  necessary for plant growth but toxic in high concentrations because it interferes with the uptake of other essential elements.

The combination of high magnesium levels and a shallow, droughty soil where the rock is at or near the surface produces conditions that only specially adapted plants can tolerate. The result is a community of drought- and magnesium-tolerant plants able to evolve in the absence of competition from more generally adapted types. The presence of multiple newly discovered species, several of them with seemingly primitive features, as well as the occurrence of others whose nearest known locations are hundreds of miles distant, suggest that this plant community is an ancient one. Indeed, these glades, with their extraordinary assemblage of rare species and at least one "dinosaur" (a plant previously believed extinct), constitute a "Lost World" in Bibb County, Alabama.
 

A. Recently Described Taxa Endemic to Bibb County

  1. Alabama gentian-pinkroot: Spigelia gentianoides var. alabamensis

  2. Cahaba daisy fleabane: Erigeron strigosus var. dolomiticola

  3. Cahaba paintbrush: Castilleja kraliana

  4. Cahaba prairie-clover: Dalea cahaba

  5. Cahaba torch: Liatris oligocephala

  6. Deceptive marbleseed: Onosmodium decipiens

  7. Ketona tickseed: Coreopsis grandiflora var. inclinata

  8. Sticky rosinweed: Silphium glutinosum

B. State Records Found Since 1992

  9. Blue wild indigo: Baptisia australis var. australis

10. Dwarf horse-nettle: Solanum pumilum (S. carolinense var. hirsutum)

11. Shining ladies'-tresses: Spiranthes lucida

12. Star-scale cloak fern: Astrolepis integerrima (Notholaena integerrima)

13. Thorne's beakrush: Rhynchospora thornei

14. Virginia nailwort: Paronychia virginica

15. Wiry beakrush: Rhynchospora capillacea

C. Federally Listed Species

16. Mohr's Barbara's-buttons: Marshallia mohrii

17. Tennessee yellow-eyed-grass: Xyris tennesseensis

D. Federal Candidates for Listing

18. Georgia aster: Symphyotrichum georgianum (Aster georgianus)

19. Georgia rockcress: Arabis georgiana

E. Other Rarities

20. Alabama croton: Croton alabamensis

21. Alabama lipfern: Cheilanthes alabamensis

22. Alabama phlox: Phlox pulchra

23. Alabama skullcap: Scutellaria alabamensis

24. Alabama snow-wreath: Neviusia alabamensis

25. Allegheny spurge: Pachysandra procumbens

26. Barrens aster: Symphyotrichum laeve var. concinnum (Aster concinnus)

27. Bay star-vine: Schisandra glabra  (S. coccinea)

28. Boykin's milkwort: Polygala boykinii

29. Bulblet bladderfern: Cystopteris bulbifera

30. Butler's quillwort: Isoetes butleri

31. Cahaba lily: Hymenocallis coronaria

32. Catesby's Bindweed: Calystegia catesbeiana ssp. catesbeiana

33. Croomia: Croomia pauciflora

34. Culver's root: Veronicastrum virginicum

35. Decumbent toadshade: Trillium decumbens

36. Eastern wahoo: Euonymus atropurpureus

37. Elliott's fan-petal: Sida elliottii

38. False rue-anemone: Enemion biternatum (Isopyrum biternatum)

39. Ginseng: Panax quinquefolius

40. Glade beardtongue: Penstemon tenuiflorus

41. Great Plains ladies'-tresses: Spiranthes magnicamporum

42. Heart-leaved plantain: Plantago cordata

43. Impressed-nerved sedge: Carex impressinervia

44. Ivory sedge: Carex eburnea

45. Jamesianthus: Jamesianthus alabamensis

46. Large-leaved grass-of-Parnassus: Parnassia grandifolia

48. Limestone adder's-tongue fern: Ophioglossum engelmannii

49. Lobe-leaved brown-eyed Susan: Rudbeckia triloba var. pinnatiloba

50. Maidenbush: Leptopus phyllanthoides (Andrachne phyllanthoides)

51. Nashville breadroot: Pediomelum subacaule (Psoralea subacaulis)

52. Needle palm: Rhapidophyllum hystrix

53. Nevius' stonecrop: Sedum nevii

54. One-flowered cancer-root: Orobanche uniflora

55. Ozark bunchflower: Veratrum woodii (Melanthium woodii)

56. Pineland gentian: Gentiana villosa

57. Plains poppy-mallow: Callirhoe alcaeoides

58. Prickly-ash: Zanthoxylum americanum

59. Purple coneflower: Echinacea purpurea

60. Royal catchfly: Silene regia

61. Shadow-witch: Ponthieva racemosa

62. Small-flowered phacelia: Phacelia dubia var. dubia

63. Smith's sunflower: Helianthus smithii

64. Smooth blazing-star: Liatris cylindracea

65. Smooth rosinweed: Silphium asteriscus var. latifolium (S. trifoliatum var. latifolium)

66. Soapwort gentian: Gentiana saponaria

67. Spring coralroot: Corallorhiza wisteriana

68. Streambank St. John's-wort: Hypericum nudiflorum

69. Streamside Barbara's-buttons: Marshallia trinervia

70. Sunnybells: Schoenolirion croceum

71. Wherry's catchfly: Silene caroliniana ssp. wherryi

72. White four-o'clock: Mirabilis albida

73. Wide-leaved bunchflower Melanthium latifolium (M. hybridum)

74. Widespread gladecress: Leavenworthia uniflora

75. Yellow least gladecress: Leavenworthia exigua var. lutea

76. Yellow-wood: Cladrastis kentukea (C. lutea)

Last Update: January 12, 2010