Shale Barren site visit

The last part of April and early May have been very rainy here in Maryland.  The spring ephemerals have done their thing and the early summer bloomers are out in force.  A lot of sedges are on the verge of being ripe as well.  The field season is well in its prime.  I’ve seen some very nice displays including the fringe trees along the Potomac Gorge not far from Washington, D.C.


Chionanthus virginicus, Fringe Tree

One particular habitat that I have visited once and hope to more in the future is the Shale Barren.  It’s an Appalachian specialty.  They occur on relatively high elevation slopes, with shale parent rock, on generally southern aspects.  The barrens are maintained by the erosion of loose rock caused by streams below that undercut them.  This creates a very hot, dry, and rocky landscape.  Several plants are endemic to these areas.  They specialize in the extreme conditions and low competition from other plants.  Most of the endemic plants of the barrens have only been described in the last 100 years.


The slight white haze in the understory is Phacelia dubia flowering in the thousands.

The picture above is what I would consider to be on the periphery of the barren.  The more rocky and less vegetated center is not seen here.  This picture does show the general habit of trees that grow here in being slightly stunted.  When I first got here I thought to myself this looks like a recently burned area.  While fire may have played a role in enlarging these barrens, they are maintained naturally by erosion.


Astragalus distortus, Bent Milkvetch. The major distribution of this one is in the central U.S. but a disjunct population is limited to the Shale Barren habitat of the Appalachians.


Trifolium virginicum, Kate’s Mountain Clover. The distinctive vegetative character for this species is the length of the leaflets in relation to their width.

The Chesapeake and Ohio Canal runs 180 river miles across the state of Maryland and contains 200 or so state-listed species within it.  Because of this I have prioritized some species based on their global rank.  My target for instance on this occasion was Trifolium virginicum.  This species is listed with a G3 rank.  That means it is considered globally vulnerable and there may be as few as 80 occurrences on the entire planet.  For this particular species, each occurrence has a small number of individuals within the population.  I was lucky enough to relocate this record and found that the population is stable.  The last time the record was updated was in 1995.  I plan on visiting more shale barrens in the future to update records for a couple other G3 species that occur here.


Viola pedata, Birdsfoot Violet. This is not a shale barren endemic but I included it to show the rocky habitat and because I liked this particular plants flower coloration.

Occasionally you will stumble upon a plant that is common but because of its stature or pure happenstance you have never seen it before.  As many times as I have been botanizing in the woods of the eastern U.S. I have never come across the following plant.  I was happy to see it in flower and add it to my photo collection.


Obolaria virginica, Pennywort. Of the Gentian Family.

Also happy 100th birthday National Park Service.  I am looking forward to the centennial celebrations this weekend at the canal including the park-wide Bioblitz.


Coleman Minney, Field Botany Intern

Chesapeake and Ohio National Historical Park

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