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New Plant Conservation Initiative at Meadowlark Botanical Gardens: the Potomac Valley Collection

Volume 3 Number 7 - December 2001
K. Tomlinson & M. N. Christmus

Meadowlark Botanical Gardens in the state of Virginia near Washington, D.C., initiated a new regional native plant conservation programme about two years ago, in its largely ornamental garden. Like most native collections, its objective is to foster conservation of native plants and their habitats through public education and display. The administration of the gardens, however, deemed it important that the new collection be highly regionalised in scope. Instead of allowing human abstractions, such as political boundaries, to define the flora of this particular region, we developed a criteria based on biogeographic factors, to define the collection. Regional geology, hydrology, climate and floristics are central to development of the collection. Within this framework, we identified the Potomac River Valley as a geographic province that determines which native plants we accession. This collection plays an increasingly important role at Meadowlark Botanical Gardens as our principal conservation initiative in support of the Convention on Biological Diversity (CBD).

Biogeographic Features of the Potomac Valley

The Potomac Valley encompasses 37,824 km sq between 38º and 40º north latitude and 80º' and 76º longitude. The river’s main course flows west to east for 640 km. Twenty major tributaries add another 1,100 km of waterways. Smaller tributaries, mainly in the mountains, combine to make-up 4,300 km of stream corridors. About fifty percent of the watershed is forested.

In global terms, the area falls within Takhtajan’s North American Atlantic Floristic Region. The Potomac River traverses five physiographic provinces west to east; these include Appalachian Highlands, Ridge and Valley, Shenandoah Valley, Piedmont and the Coastal Plain. Each of these regions contains unique plant communities. In some cases, these communities enjoy broad protection in national and state parks. In other areas, plant communities are under siege from urban sprawl, grazing and logging. Takhtajan recognizes almost one hundred taxa as “endemic or nearly endemic” to the North American Atlantic Floristic Region. Many of these taxa are illustrative of the Potomac Valley flora and comprise an important part of our current accessions activity.

The Appalachian highlands of the Potomac Valley reach 1200 m. Relict alpine communities, red spruce and northern hardwood forest occupy this region. Several northerly taxa reach their southern limit in the Appalachian Highlands. Within the Ridge and Valley Province, plant communities called shale-barrens support many unique species. Among these are the endemic Phlox buckleyi, Trifolium virginicum and Senecio antennariifolius, to name a few. Further east, in the broad Shenandoah Valley, limestone outcrops support many calcareous cliff-dwelling species. Ferns are of particular interest in this area. One of our region’s most unique small shrubs, Cliff Green (Paxistima canbyi), is also at home on these limestone formations.

The eastern portion of the Potomac Valley lies within the foothill-like Piedmont and the alluvial Atlantic Coastal Plain. Vast deciduous forests of white oak, red oak, red maple, American beech and rock oak embrace a diversity of shade-loving lower-canopy trees, shrubs, wildflowers and ferns. Bald cypress trees grow here, very near their northern limit. Some areas of the eastern Piedmont and the Coastal Plain are widely developed. The need for conservation of native plant communities in this area is immediate.

Combining Existing Resources and Developing New Ones

No flora for the Potomac Valley currently exist, however, within the four states of which the Potomac Valley is a part, three—including Pennsylvania, West Virginia and Maryland—have floras. Virginia has no systematic treatment of its flora, but it does have a very useful flora atlas. We use these four resources, along with topographic maps, geographic information systems and fieldwork to determine species composition and distribution within the watershed. In addition, we consult with various private and government agencies working to conserve plant diversity in all four states. This exchange enables increased communication on both ex situ and in situ conservation projects. Through this process, we are developing new detailed information on the composition, distribution and conservation status of the Potomac Valley plants. Ultimately we intend to develop a database for this information.

The display and interpretation of native species is a central goal of the collection. The collection will provide our staff with the ongoing task of understanding conservation needs of native species throughout the Potomac Valley and interpreting that information to the public through education programs. We will continue to add accessions in accordance with various strategies outlined in International Agenda for Botanic Gardens in Conservation and the Darwin Technical Manual.

From a programmatic perspective, the Potomac Valley collection is the foundation of our institutional mission centred on aesthetics, conservation, education and community service. Moreover, this collection’s development supports Meadowlark’s parent agency, the Northern Virginia Regional Park Authority, in conserving and cataloguing native species on its own properties, all 4,583 hectares of which are in the Potomac Valley.

Objectives for the Potomac Valley Native Plant Collection

  • Strengthen the existing collection within the fiscal, administrative and curatorial practices of the garden.
  • Foster an understanding of the aesthetic and ecological value of native plants within the community.
  • Develop and implement educational programmes that focus on native plant horticulture and conservation.
  • Provide conceptual framework for the public to foster awareness for regional plant conservation with issues such as water quality and ecosystem/habitat conservation.
  • Facilitate a temporal understanding about the Potomac Valley plant communities by interpreting their natural history.
  • Raise public awareness about obtaining native plants and discourage wild collecting.
  • Encourage in situ and ex situ conservation projects throughout the Potomac Valley.
  • Work in partnership with local universities, museums and other gardens to encourage systematic, ecologic and biogeographic research on Potomac flora.
  • Establish curatorial and horticultural internship programmes working with the Collection.
  • Illustrate the effects of exotic invasive species on native plant communities.
  • Propagate stock plants for reintroduction into the wild when deemed appropriate.
  • Rescue plants from construction sites and other disturbed areas when all viable conservation alternatives are exhausted.
  • Research and assemble criteria to evaluate the collection’s impact as a vehicle for conservation and education.