Last weekend, members of the B. W. Wells Association and the Friends of Plant Conservation toured the Picture Creek Diabase Barrens in Granville County, North Carolina. The field trip was sponsored by Rob Evans and the state Plant Conservation Program and was led by Harry LeGrand of the North Carolina Natural Heritage Program and Rob. Dr. LeGrand has a long history with Picture Creek and was recently honored when a new species of Marshallia, which he discovered there, was named for him.
Harry LeGrand is on the left with the orange cap in the photograph below.
The Picture Creek Diabase Barrens is characterized as a small remnant of what was once a widespread Piedmont Prairie. Its 407 acres are home to a large number of plants that are listed as rare, endangered or threatened. Thus it is considered a Nationally Significant natural area. The occurrence of so many unique plants in this site is due primarily to the relatively rare mafic soils that are associated with shallow incursions of diabase rock. Over the past years, prescribed burns have been added to improve the habitat for rare species.
Picture Creek is probably best known for the federally endangered Smooth Coneflower – Echinacea laevigata. The population here is the largest known in the world. This year, the population at Picture Creek was just beginning to bloom; the two photos below are from a previous year at the same time and place.
Although the new species of Marshallia – Marshallia legrandii (Tall Barbara’s-buttons) – is not federally listed yet, it is a significantly rare plant, with only 2 known populations in existence, one at Picture Creek and one in Halifax County, Virginia, on similar mafic soil.
The separation of a new species may sometimes be based on significant but subtle differences in structure and behavior that might not be readily visible. But Marshallia legrandii is easily distinguished from its neighboring relatives by its greater height (hence the name Tall Barbara’s-buttons), large flower size, and its much deeper pink flower coloration. It also blooms almost a month later than its nearest relatives.
Below is a photograph of the flower of a common Marshallia in this area of the Piedmont – Marshallia obovata. It has been blooming for the last week or two. Note the small hints of pink or purple on some of the petals and the small size of the flower.
In contrast, Marshallia legrandii has a larger flower and much deeper pink or purple coloration on the petals. It is not blooming yet this year, so the photos are from a previous year in the same location.
Baptisia australis var. aberrans (Eastern Prairie Blue Wild Indigo) was in full bloom in the open glades. In the photo directly below, the large leaves of Silphium terebinthinaceum (Prairie Dock) can be seen directly behind the Wild Indigo. Both are state protected plants.
A closer view of the blooms of the Wild Indigo.
Phlox glaberrima (Smooth Phlox) was also blooming in good numbers in the open glades. This is one of the many species that have thrived and expanded since prescription burns were resumed at Picture Creek. Although it is not a state protected plant, it is uncommon in the Piedmont.
The woodland edges get enough sun from the open glades to allow shrubs like Rhus aromatica (Fragrant Sumac) to bloom and produce berries. Pictured below are the bright red berries of Fragrant Sumac, a sight not often seen in the shaded woodlands. Notice the hirsute (fuzzy, hairy) nature of the berries.
Blephilia ciliata is a woodmint that specifically thrives on diabase soils. In fact, one of its common names is Diabase Woodmint. It is also known as Pagoda Plant, and Downy Wood Mint.
The Picture Creek Diabase Barrens is owned by the State Department of Agriculture and managed by cooperating divisions within the Department. There is also a long history of assistance from the Natural Heritage Program and the North Carolina Museum of Natural Sciences. Further management steps are still ahead, to enable this unique prairie remnant to be preserved and restored.