Alabama is an Eden for North American biological diversity. The state ranks 5th in the nation for biodiversity, and has more species than any other state east of the Mississippi River. Some of the greatest treasures in this assemblage are the state’s endemics – those species found only in Alabama. Alabama has 22 species of endemic plants, 28 if you include plant subspecies and varieties. Several other taxa are primarily found in Alabama, but have small populations in another state. Regrettably, many of these rare plants are at risk of extinction.
By providing safe refuge, the Birmingham Botanical Gardens is helping to ensure these species will survive. In addition to providing a haven for Alabama’s endemics and other rarities, The Gardens are an active supporter and founding member of the Alabama Plant Conservation Alliance, a consortium of organizations and individuals committed to protecting Alabama’s native plants and their ecosystems. At The Gardens, you can find 5 species plus 6 subspecies and varieties. The BBG Conservation Plan outlines their current efforts in conservation and propogation of endemic plants. Each of these plants has a unique life history and the stories of several of them are described below.
The Gardens include the state’s only endemic tree species – Boynton’s Oak (Quercus boyntonii). This rare, small-statured oak (some consider it a shrub) occupies dry oak and pine woodlands in portions of Alabama’s mountains, especially on or near exposures of sandstone. It can be seen in the wild at two other Trek Birmingham sites, Oak Mountain State Park and Moss Rock Preserve. The species has been neglected in earlier treatments of southeastern trees, and frequently confused with similar species, but is now widely recognized as a distinct species. There’s also been confusion about its distribution owing to a single specimen reported from eastern Texas. The specimen has been lost, and field surveys where it was reported in Texas have failed to find Boynton’s Oak, though similar species were found. Thus, many botanists have concluded that this was a case of mistaken identity and that the species is endemic to Alabama. Owing to its limited distribution, Boynton’s Oak is considered endangered by the International Union for the Conservation of Nature (IUCN).
Spleenworts are small ferns thriving in cool, moist, and shady microhabitats, especially rock outcrops. Several species are found in Alabama, and one of them is an endemic. Tutwiler’s spleenwort (Asplenium tutwilerae) is known from only one spot, a small valley known as Havana Glen in Hale County. The plant grows on exposures of a rock known as puddingstone, a conglomerate rock formed of iron-rich sandstone with embedded pebbles of rounded chert. The fern was discovered by a famous Alabamian, Julia Tutwiler, known among historians for her efforts to promote education and reform prisons. Tutwiler and other botanists scoured the area, but no other population of the species was ever found.
The heartleafs, or gingers, (genus Hexastylis) are peculiar little plants of the forest understory. They have heart-shaped leaves of deep green that sprout in clusters directly from the root. Their flowers, which rest on the ground, resemble small brown vases when growing, but split open to reveal a display of red and white when mature. The genus is endemic to the southeastern US, and contains ten species. Three of these species are found in Alabama, and Harper’s Heartleaf (Hexastylis speciosa) is endemic to the state. The species was discovered early last century by one of Alabama’s most famous botanists and ecologists, Roland Harper. The species is known from a cluster of counties north of Montgomery in an ecoregion known as the Fall Line Hills. It inhabits moist microhabitats in a variety of forest and woodland ecosystem.
One of the endemic subspecies found at The Gardens is also one of the strangest of Alabama’s plants. The Alabama Canebrake Pitcher Plant (Sarracenia rubra ssp. alabamensis) is one of a handful of carnivorous plants in the state . The plants trap insects and other small animals, then digest them with enzymes like those in your stomach. Pitcher plants create pitfall traps with a tubular leaf filled with water and digestive enzymes, and lined with downward pointing hairs and slick sides. Prey is drawn to the trap via bright colors and irresistible odors. Pitcher plants and other carnivorous plants still get their energy from sunlight via photosynthesis, but they practice carnivory to obtain nutrients that are scarce in the bogs where they grow. The Alabama Canebrake Pitcher Plant is considered by some to be its own species, but most classify it as a subspecies of a species with much broader distribution.
The Alabama Croton (Croton alabamensis var. alabamensis) is a shrub variety endemic to just a handful of counties in central Alabama. The only other population of the species is a different variety growing in a few canyons of central Texas. In Alabama, it grows on or near outcrops of limestone, dolomite, and shale, usually along river bluffs. The leaves of this handsome shrub look ordinary from above, but flip them over and they are shiny silver. In late summer and fall, dying leaves turn yellow and rosy red. With these good looks and its ease of cultivation, the Alabama Croton has become a popular plant among southeastern gardeners.
There are several species of rare, near-endemics harbored at The Gardens that deserve mention. One of the state’s most beautiful near-endemics is the Alabama Larkspur (Delphinium alabamicum). The larkspur favors sunny or partially-shaded habitats with soils derived from limestone in Alabama and Georgia. When it flowers, it grows a stalk adorned with exquisite azure or deep blue-violet flowers.
One spectacular near-endemic sheltered at The Gardens is the Giant Whorled Sunflower (Helianthus verticillatus). This exceptionally tall wildflower – 12 feet at maximum height – was discovered in 1892 in the Coosa Valley but then disappeared when agricultural practices spread and fire-suppression was practiced in surviving woodlands. Though believed extinct for many years, it was rediscovered when remnants of the Coosa Valley Prairie ecosystem were discovered the 1990s. Soon thereafter, a small nearby population was found along a roadside in Alabama.
One endemic at The Gardens is a species found only in Bibb County, Alabama, and only in the Ketona Dolomite Glades. Glades are naturally treeless habitats maintained primarily by bedrock at or near the surface preventing tree establishment. The Ketona Dolomite Glades were discovered in 1992. These particular glades are only found in a small swath of land along the Little Cahaba River, and several are protected by the Alabama Chapter of The Nature Conservancy. Thus far, nine plants new to science have been discovered there. One of these is the Ketona Tickseed (Coreopsis grandiflora var. inclinata). Species in this genus produce bright yellow to orange-yellow flowers with jagged-edged petals. The Ketona Tickseed blooms in early spring before the annual May-June drought. Like all glade wildflowers, it has a variety of traits that help it survive in harsh, hot environments, including its very narrow leaves. Perhaps its reclining posture – one of its most distinctive features – also helps it contend with the glade’s harsh environment, but how it helps remains a mystery to science.
– R. Scot Duncan