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Harperella
Ptilimnium nodosum
Family: Apiaceae
Description: Harperella can be distinguished from other members of the Apiaceae by its hollow, quill-like leaves. Leaves are 1-5 inches (2.5-12.5 centimeters) in length, and are very narrow and delicate. Plants can attain a height of 1-2 feet (0.3-0.6 meters) and may occur singly or in large clumps along rocky shoals of clear, swift-flowing streams. During periods of high stream flow, plants may be stripped of their leaves, flowers, fruits, and even stems. New flushes of leaves and stems may appear throughout the summer and into the fall. The white flowers are arranged in umbels, similar to those of Queen Anne's Lace, but are fewer in number and more delicate. Harperella flowers from July to August with seeds produced in late summer or fall. Dispersal of seeds is aided through the action of flood waters. Pollination biology of the species has not been studied, but seed set is apparently profuse in this annual since populations in localized areas can achieve a high density and number of individuals each year.
| Status: |
Federally Listed Endangered (September 28, 1988) Global Rank: G2 State Rank: S2 |
Distribution: Half of this species known populations have been destroyed. The remaining populations are scattered across Alabama, Arkansas, Georgia, Maryland, North Carolina, South Carolina, and West Virginia. Discovered in Arkansas in 1990, harperella is known from five counties (Garland, Montgomery, Perry, Scott, and Yell) in the Ouachita Mountains. Arkansas's populations represent the western limit of this species known range.
Habitat: In Arkansas, harperella occurs along seasonally flooded rocky streams of the Ouachita Mountains. Plants are generally found in microsites (rocky shoals) sheltered from the erosive effects of rapidly moving water. Since flooding along streams can alter the distribution of these microsites, harperella populations seldom persist in one specific location for a number of consecutive years. Instead, populations of this plant tend to shift in accordance with the distribution of suitable habitat.
Conservation Status: Harperella grows along rocky shoals of clear, swift-flowing streams. In such places, harperella requires a narrow range of hydrologic conditions, neither too deep nor too dry. Dependence upon specific water depths, and good water quality, have made populations of this species extremely vulnerable to upstream development, changes in water usage and flow, and water quality degradation. Primary threats to harperella center on changes in water flow and water quality. Dams, reservoirs, and other water impoundments and diversions can alter the narrow range of water levels required by this species. Likewise, degradation of water quality through siltation can damage existing populations. Protection of habitat where this species is known to occur is essential. However, such protection should take a broad view (entire stream) in light of this species tendency to "move" along a stream in response to the availability of appropriate microsites.
