© Bruce McNitt/Panoramic Images (Virginia)
Shale-Barren Rockcress
Shale-barren rockcress is an imperiled plant that occurs sporadically in just a few counties of Virginia and West Virginia. Fewer than 60 populations reside in the wide-open shale barrens it requires.
Description
This slender biennial flowers from July to September and is a member of the mustard family (Brassicaceae). It is also an herb, characterized best in its nonreproductive stage by its inconspicuous basal rosette of lobe-shaped leaves, ranging in size from 1.6 to 3.5 cm.
In its reproductive state the leaves shrivel and “bolt” while becoming rather inflorescent. A mature plant grows 41 to 97 cm (18 to 48 inches) tall with small whitish flowers, calyxes and bearing fruits (siliques); becoming yellowish brown seeds of a narrow elliptic shape.
Habitat
A shale barren is comprised of shale deposits on a south-facing slope, of 20-70 degrees, at an elevation of 1300-1500 feet (400-600 meters) within the mid-range of the Appalachian Mountains. These features along with the foundation of hard weather resistant shale or siltstone fragments define a shale barren.
This habitat supports a bare, sparse, and scrubby growth of plants. There is adequate moisture due to the shale sub strata layers but an adverse surface layer for germination and establishment of plants. It is the temperature of the surface layer that supports germination; a high surface temperature.
Shale-barren rockcress does not like competition or encroachment; such as Centauria maculate or many grasses.
Life Cycle and Reproduction
The Gypsy Moth is a pollinator to the Shale barren rockcress, and this insect is greatly impacted by the spraying of insecticides; one long lasting and another impacting Gypsy moth larvae. Other pollinators include bees and small insects such as surfed flies. Infestations would greatly impact the lifecycle and reproduction of this endangered plant due to its small population size and specialized habitat.
Sheep, goat, and deer are considered pests to the shale-barren rockcress, as all three find it tasty grazing. Shale-barren rockcress reproduction is further threatened by drought and over-collection by botanists.
Conservation
The shale-barren rockcress Listed as a Federally Endangered Species on August 8, 1989, and is also listed as endangered in the State of Virginia. Within the Commonwealth, its communities have been at least partially destroyed by road and railroad construction, the damming of a stream, and even a hiking trail that crossed one community. All of this on public land that now is protected. Sites in the George Washington National Forest are designated as Special Interest and Special Management Areas, as is another site designated as a Natural Area Preserve owned by the Commonwealth of Virginia.
Similar Species
Arabis laevigata var. burkii is often confused with Arabis serotina and also shares a shale barren habitat, but Arabis laevigata grows in a larger variety of habitats and blooms in April and May. Arabis serotina blooms mid-July to September, as well has narrower leaves, smaller flowers, and the inflorescence is more branched.
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