Sunday, June 1, 2014

Diabase Rocks!

Diabase is an igneous rock type found in isolated bands in the Piedmont of North Carolina.  Some of the largest expanses are found in Durham and Granville counties. In these areas, boulders may be common and the soil surface is often interspersed with rocks.  The soils tend to be high in nutrients such as magnesium, have clayey textures, and shrink-swell properties.

(The boulder shown to the right occurs along the edge of a diabase sill in Durham County)

Many unusual and/or North Carolina rare plants may be found on diabase. A few of these are shown below.

Eastern Prairie Blue Wild Indigo (Baptisia australis var. aberrans): Globally rare & listed Endangered in North Carolina. Scientific nomenclature for this plant has varied through time and may continue to evolve. See Weakley's 2012 Flora for a discussion. Image from Durham County, NC
Tall Larkspur (Delphinium exaltatum): Ranked as globally vulnerable by NatureServe and listed Endangered in North Carolina. This image was taken at North Carolina's only remaining Piedmont population; the site in Durham County is now a Plant Conservation Preserve.
Crested Coralroot (Hexalectris spicata): Durham County, NC - wide-ranging & apparently globally secure, but significantly rare in North Carolina.
Hoary Puccoon (Lithospermum canescens); Limited to 2 NC counties and listed as Threatened in North Carolina

Low Wild-Petunia (Ruellia humilis): Widespread in US, but confined to a few Piedmont counties in North Carolina where it is listed Endangered. At least 2 populations are now protected on Plant Conservation Preserves. Image from Granville County
Smooth Coneflower (Echinacea laevigata): Federally and state endangered, extirpated from 2 states in its former range. Smooth Coneflower has been a focal species of conservation efforts in the Durham area since 2004.

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