Exploring the Millboro Shale Formation: A Treasure Hunt for Endemic Plants

I had been wanting to make a trip to Bath County to explore shale-barrens for a couple of years, so I was very excited to finally be visiting one.  Drew and I climbed up a steep slope, trying not to dig our feet into the loose shale too much, towards the light green of the herb layer ahead.  The canopy opened up around us as we neared the top of the mountain.  The only trees in site were gnarled old eastern redcedars growing out of the rocky ground, and the occasional chestnut oak, northern red oak or Virginia pine.  Large rock outcroppings pierced the shaley ground, covered in blunt-lobed woodsia and rock spikemoss.  Would we find what we were looking for?

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Shale-barren in Bath County.  Note the shale-barren wild buckwheat (the big fuzzy leaves and stalks growing on the center of the big rock).

Shale-barrens occur on hot, dry, south facing slopes in the Mid-Atlantic states of Pennsylvania, Maryland, West Virginia and Virginia.  They are characterized by shaley soils, with many small pieces of broken up shale on the surface of the ground.  Shale-barrens are too dry for most tree species to grow, leading to a very sparse, open canopy.  However, many species of herbaceous plants are specifically adapted to shale-barrens, growing in no other habitats.  These shale-barren endemics are confined by the small range of their habitat, so many of them have relatively few populations, making them vulnerable to extinction.

Two of the shale-barren endemics I was most excited about seeing were the white-haired and Millboro Leatherflowers (Clematis albicoma and C. viticaulis respectively).  Both occur only on shale-barrens, C. albicoma only in Virginia and adjacent West Virginia, and C. viticaulis only in Bath, Augusta and Rockbridge Counties in Virginia.  They are both small, semi-woody plants.  They have opposite rounded leaves, beautiful drooping flowers and incredible spiraled seed-heads.

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Clematis albicoma seed-head in its full glory.

On our drive out, we had watched the road bank for interesting flowers on the long, winding road in Bath County.  Suddenly a splash of pink appeared, perhaps a phlox of some type?  We marked the spot in our memory so we could check it out on the way back.  We passed several places where the road banks were covered in loose shale flakes, telling us we were now on a shale formation.

Once we emerged from the forest onto the shale barren, we began to look around for the white-haired leatherflower, and I soon spotted a large clump growing on a nearby rock.  We were disappointed to find it had already flowered, but its elegant spiraled seeds made up for it.

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White-haired Leatherflower (Clematis albicoma)

As we were photographing the white-haired leatherflower, I noticed several clumps of Kate’s mountain clover growing on the rock above it.  Kate’s mountain clover (Trifolium virginicum) is endemic to rock outcrops in the Mid-Atlantic states, but unlike many other shale-barren plants, it can grow on types of rock other than shale.  For instance, at a site in Loudoun County that I wrote about earlier this year, it grows on a diabase outcropping.

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Kate’s Mountain Clover (Trifolium virginicum)

We continued to carefully pick our way through the barren, pausing here and there to examine plants.  Large mats of shale-barren pussytoes (Antennaria virginica) grew everywhere — sometimes we had to work hard to avoid stepping on them.  Clumps of shale-barren wild buckwheat (Eriogonum allenii) were also abundant; their large, leathery leaves stood out against the wiry leaves of the pussytoes.  The brilliant purple and yellow flowers of downy wood mint and Maryland hawkweed added the occasional splash of color to the scene.  I examined one of the large rocks closely, finding maidenhair spleenwort and moss phlox mixed in with the blunt-lobed woodsia and thick mats of rock spikemoss.

All too soon it was time to go, as we had one more important stop planned.  As we drove back down the road, we kept our eyes out for the mystery phlox we’d seen on the way in.  Suddenly a flash of bright pink appeared on the road bank.  We scrambled out to take a look.  This plant had brilliant pink, five-petaled flowers and super narrow, lance-shaped leaves.  A quick look at the key in the Flora of Virginia confirmed our suspicions: this was the state rare sword-leaved phlox (Phlox buckleyi), an endemic of shale woodlands.

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Sword-leaved Phlox (Phlox buckleyi)

Our final stop of the day was another road bank, also in Bath County.  This stop was the site for Millboro leatherflower, one of the rarest plants we could see that day.  We hoped it would sill be blooming, as its seeds are not nearly as beautiful as white-haired leatherflower, in my opinion.  We turned onto the road and began slowly driving up it, scanning the shaley banks on either side for leatherflowers.  We were getting close to the end of the road when Drew spotted the first one.  We leapt out of the car and ran over to check it out.  It was still blooming, its drooping, purple, tube-shaped flowers in pristine condition.  Soon we found several more nearby.

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Millboro leatherflower (Clematis viticaulis)

The Millboro leatherflowers were growing right out of the shale flakes with common wild quinine and New Jersey tea.  The leatherflowers were so close to the roadside that it looked like one bad land slide was all that it would take to destroy the population.  I wondered how many other sites for this rare and beautiful flower there could be given its very specific habitat requirements and its tiny, three county range.  They seemed to be thriving on that road bank despite conditions too harsh for many other plants.  Hopefully they will continue to do well…

 

Loudoun County Piedmont Diabase Barren: A Rare Ecosystem Faces Threats from Development

I have been fascinated by plants and the natural world for as long as I can remember. Since I was a toddler, my mom would take my little brother and me to a nearby park almost every day to play in the woods, fields, and creeks.  These days, a fellow plant-loving friend and I meticulously research and plan trips all around the state to look for new plants and plant communities.  More than a year in advance, we planned a trip to the amphibolite outcrops of Naked Mountain Natural Area Preserve to see hundreds of blazing star plants in bloom.  That trip was soon followed by an exciting late May trip to Difficult Creek Natural Area Preserve to see the diverse southern piedmont prairie and search for rare tall Barbara’s buttons (which we found!)  Piney Grove Preserve, Chub Sandhill Natural Area Preserve, Shenandoah National Park, George Washington National Forest, and Grayson Highlands State Park are some of the other preserves and natural areas that I have visited this year looking for plants.  

One reason I like plants so much is because they form the basic, tangible foundation for nature.  Native plants create and define different ecological communities, which host all the other life forms, which have co-evolved with the plant species in the community.  Witnessing the seemingly never-ending diversity of plants and the rich multi-species relationships of native plant communities is a source of great joy and mystery for me.  There are few things I find more rewarding than researching and planning a trip to find a rare plant and then successfully discovering it growing where I thought it would.  I also love the challenge of learning and identifying the huge number of plants native to our state.  

I recently learned that Loudoun County’s Board of Supervisors is voting on January 18th on a proposal to raze a Piedmont Mafic Barren growing on a diabase formation on the banks of Goose Creek, in order to build a 750,000 square-foot data center.  These barrens consist of two small separated outcroppings of diabase bedrock.  Around the two barrens grows a stunted forest of eastern redcedar, white ash, eastern redbud, and fragrant sumac.  The outcrops themselves are covered in dense patches of mosses and lichens, and sparse herbaceous plants such as Appalachian phacelia, awned flatsedge, and the state rare Central Appalachian endemic, Kate’s mountain clover.  

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Kates Mountain Clover (Trifolium virginicum) © Lonnie Murray

I was greatly disturbed by this news, as there are only 10 documented occurrences of Piedmont Mafic Barrens in the world, all of them in the Piedmont of Virginia.  The Goose Creek site has the additional distinction of being the most northern example of this plant community, defining its range.  The Piedmont Mafic Barren plant community is ranked by the Virginia Department of Conservation and Recreation as G1/S1, which means that it is critically imperiled globally.

Virginia is broadly divided into five physiographic provinces.  From east to west, these are the Coastal Plain, Piedmont, Blue Ridge, Ridge and Valley, and Allegheny Plateau provinces.  The landform, geology, and plant community types define the character of each of these regions in much the same way that historic buildings and architectural districts define the distinct character of cities and towns.  Loudoun County, of course, is in the Piedmont province.  Destroying the plant communities that make the Piedmont unique, such as the Piedmont Mafic Barren in Loudoun, degrades the essence and character of the Piedmont province.

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The Loudoun County Piedmont Mafic Barren, © DCR-DNH, Gary P. Fleming.

I hope the Loudoun Board of Supervisors will deny the rezoning application and do all they can to protect the Piedmont Mafic Barren area.  Whether I ever have the opportunity to visit it or not, its existence enriches my sense of place and offers an open invitation for exploration and discovery.  While I’m interested in all plants, the ones that grow where I live are the most important to me.  Knowing the plant communities of the piedmont makes me feel at home and helps give me a sense of belonging to the natural world.  It heightens my appreciation of my surroundings every time I go outside.

I think if more people had the chance to experience the natural beauty of the Piedmont they would appreciate it more, and work harder to protect it.  While we don’t know all the contributions any particular species or community makes to the ecosystem services we all depend on, we do know that each piece of the puzzle is valuable to the functioning of the whole.  I hope that the Loudoun County Board of Supervisors won’t take away the opportunity to experience and learn from the Piedmont Mafic Barren from present and future generations.