Magnolia Bogs of the Fall Line

Sponsoring Organization: Virginia Native Plant Society, Potowmack Chapter (www.vnps-pot.org)

Speaker: Rod Simmons

Fall Line Magnolia Bogs are a globally-rare type of upland seepage wetland uniquely associated with Potomac Formation soils and acidic terrace gravel forest communities of the fall line. In 1918, W.L. McAtee described the “magnolia bogs” as a distinctive habitat present in a few dozen places along the innermost coastal plain and fall line of the Washington, D.C. region.

Occurring where cool spring water seeps from vast, upland aquifers of sand and gravel deposits over impervious clay, these specialized wetlands are characterized by the presence of Sweetbay Magnolia (Magnolia virginiana) and a diversity of other distinctive plants, such as Peat Moss (Sphagnum spp.), Poison Sumac (Toxicodendron vernix), Swamp Azalea (Rhododendron viscosum), and many others.

Jim Long and giant Cinnamon Fern (Osmundastrum cinnamomeum) stand at Araby Bog, Charles County, Maryland. Photo by R.H. Simmons.

This natural community of Virginia, D.C., and Maryland is now “Critically Imperiled” globally and statewide, ranked G1/S1. While many of McAtee’s localities have been destroyed or badly degraded by development over the past decades, a few good examples remain, including Barcroft Bog in Arlington County, Lorton Bog in Fairfax County, and others.

Rod Simmons, plant ecologist and Natural Resource Specialist with the City of Alexandria, will give a presentation on Magnolia Bogs throughout their range, associated flora and fauna, including rare and historical species, conservation and management, and some new discoveries in Alexandria and elsewhere.

The meeting is free and open to the public. Registration is not required.

Location: Green Spring Gardens

Directions: From western Fairfax County or Maryland, take the Capital Beltway (495) to Braddock Rd. (Rt. 620) east exit. Follow Braddock Rd. northeast for several miles, crossing Little River Turnpike (Rt. 236). After this intersection get in right lane and proceed slowly to Green Spring Gardens entrance a very short distance on right at 4603 Green Spring Road, Alexandria, VA 22312. 703 642‐5173.

From Shirley Highway (395) at the western end of Alexandria, take Duke St. (Rt. 236) west exit and head west on Duke St. (soon becomes Little River Turnpike) towards Pinecrest and Annandale. Turn right at the intersection with Braddock Road and follow the directions above.

More Information: on the geologic setting of the Magnolia Bogs in the City of Alexandria and Arlington and Fairfax counties, see “Lincolnia silty clay”, “Barcroft diamicton”, “Winkler sand”, “Chinquapin Hollow fine sandy clay”, and “Arell clay” in Plate 4: Potomac Formation Expanded Explanation (Fleming 2008) and Plate 5: Surficial Geology and Landforms: Expanded Explanation (Fleming 2008) at http://alexandriava.gov/22560.

For ARMN spring class and members, this presentation applies towards advanced training hours in botany, geology, and forest ecology.