Some trees just dig heavy metal. On the west side of Piney Meetinghouse Road near Glen Road, they’re not afraid show it.
“The vegetation you see in that area is so different. … The oak trees that you see look a lot smaller and scrubbier,” said Steve Findley, a naturalist at Locust Grove Nature Center. “Tulip poplars drop out completely.”
That’s because they grow in serpentine barrens, a geological condition consisting of serpentine rock with shallow soil that is highly acidic.
Serpentine barrens might not be as dramatic a sight as a white deer or a lonely 17-year cicada flying around in the 18th year, but the rare terrain may be the geological equivalent of these natural rarities.
Magnesium, chromium and other heavy metals are in high concentration in the area naturally, repelling some common plant species in the area and attracting some rarities that thrive in it. Post oak and blackjack oak trees grow in Potomac’s serpentine barrens. “You go through the rest of the county, and you just don’t find those trees,” Findley said.
“They occur just sporadically on the piedmont up and down the east coast,” Findley said.
Potomac’s serpentine barrens are home to 23 different rare, threatened or endangered plant species. Some portions of the serpentine barrens are protected under the National Capital Park and Planning Commission’s Legacy Open Space program.