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Conservation Collections at Meadowlark Botanical Gardens, U.S.A: Supporting The IABGC

Volume 2 Number 2 - July 2005

Keith P. Tomlinson, Gary Becht & David Z. Brodkey

Meadowlark Botanical Gardens in Vienna Virginia, U.S.A. has created three distinct native plant collections in support of the International Agenda for Botanic Gardens in Conservation. The largest of these is the Potomac Valley Collection (PVC). The PVC development is based on biogeography and floristic composition within the Potomac River basin (see BGCNews 3(7), June, 2001). Whereas, the Virginia Native Tree Collection (VNT) and the Virginia Native Wetland collection (VNW) include species that occur within the state as a political unit.

Virginia is topographically and floristically diverse. The Appalachian Mountains in the southwest region of the state reach elevations of 1600 meters. Many other peaks in the west are more than 1200 meters high. West to east the state traverses six distinct geographic regions. These include the Appalachian Highlands, Valley and Ridge, Shenandoah Valley, Blue Ridge, Piedmont and Coastal Plain. The Coastal Plain area is represented by most of the Chesapeake Bay and reaches the Atlantic Ocean further east. The entire state is located between 36-40° N and 74-83° W. In Takhtajan’s Floristic Regions of the World, Virginia occupies the Appalachian Province and the northern tip of the Atlantic and Gulf Coast Plain Province. Virginia is a state where bromeliads reach their most northerly distribution, cacti adorn beach dunes, endemic birches are found and northern spruce forests dominate the highest mountains. It is also a state in need of both in situ and ex situ conservation. A principal goal of these collections is to educate the public about the connection between garden conservation collections and saving plants in the wild.

The Virginia Native Wetland (VNW)

This collection is located in and around a small wetland called Lake Lena at the lowest elevation in the Gardens.  The native biota of Lake Lena is an ideal classroom for educational programmes focused on Virginia’s native wetlands and the need for conservation. No horticultural selections are used in this collection. Conservation work began in 1999. Several native trees were already established on the site when the boardwalk was installed adjacent to the lake over ten years ago.  Among these are numerous bald cypress trees (Taxodium distichum).  These trees have grown well and developed their trademark "knees" on the water’s edge.  Sycamore (Platanus occidentalis), black gum (Nyssa sylvatica), river birch (Betula nigra), black willow (Salix nigra) and sweet gum (Liquidambar styraciflua ) also grow in the area. Many of Virginia’s most southerly wetland shrubs and wildflowers are on exhibit here.

Lake Lena is a place of solitude in the garden – a place where native plant horticulture and habitat conservation blend to create a naturalized wetland. Aquatic native plants such as pickerelweed (Pontideria cordata), native fragrant water lilies (Nymphaea odorata), arrowhead (Sagittaria latifolia) and sweet flag (Acorus calamus) flourish in summer’s humidity.  On the lake shore, carnivorous pitcher plants (Sarracenia purpurea), red and blue cardinal flower (Lobelia cardinalis, L. siphilitica) and blue flag iris (Iris versicolor), souring rush (Equisetum hyemale) mingle with aromatic bayberries (Myrica pensylvanica). Many widespread wetland species are naturalizing around the lake, including cattails (Typha latifolia) and numerous native sedges (Cyperus spp. and Carex spp.).

Lake Lena also provides a habitat for aquatic animals and birds. Several species of turtles, northern water snakes and native frogs inhabit the area. Many native fish and aquatic insects coexist with the plants. Wading birds frequent the lake.  Great blue herons, green herons and black crowned night herons enjoy secretive hunting on the water’s edge.  A full assortment of perching birds frequent the lake too.

The Virginia Native Tree Collection (VNT)

The Virginia Native Tree collection resides in a far corner of the gardens. Here visitors can see some of the State’s best native trees for use in the home setting.  Several smaller native trees make up a good part of this collection. The fringe trees (Chionanthus virginicus), native members of the olive family, routinely amaze visitors with their fragrant, strap-like white flowers.  In the fall, these trees display a dark blue ovoid drupe. This is an ideal tree for the discerning gardener with a small yard.

Growing close by are several paw paws (Asimina triloba).  These handsome little trees are familiar to people who spend time along local rivers where it grows in abundance.  The long, broad leaf tapers neatly to a "drip tip," a feature that illustrates its tropical origin as a member of the Annonaceae.  When crushed, the leaves have a distinctive odor reminiscent of diesel fuel.  The fruit is a large oblong berry with a slightly coriacious green or brown rind.  The mesocarp is white and creamy, often described as a mix between apple and banana with large black seeds.  Paw paw is widely regarded as Virginia’s finest indigenous fruit.

Other trees in this collection include the hop hornbeam (Ostrya virginiana), a hazelnut relative with soft shaggy bark. Also from the Corylaceae is the hornbeam or muscle wood (Carpinus carolinana).  This tree is notable for its extremely hard wood and fine twigs with delicate imbricate buds. Muscle wood is slow growing and, with age, provides a beautiful fluted trunk. Further along the trail, is overcup oak (Quercus lyrata), so named as the imbricate involucre on the acorn covers nearly the entire nut.  A tree with highly variable cruciform leaves, it is a good candidate for low, wet sites.

The sweet-bay magnolia (Magnolia virginiana) grows nearby.  Found from Massachusetts to Florida, sweet-bay magnolia varies in size, attaining much larger stature in the south.  In time, sweet-bay becomes a handsome yard tree.  The early summer flowers are creamy white and very fragrant. Several other native trees are in this collection, which is located below the Hillside gazebo, about a ten-minute walk from the Visitors Center.  The VNT is one of the featured collections in our Specimen Tree programme.

Collection Based Education for Conservation

In the United States, amateur gardeners are constantly encouraged to use horticulture selections by the popular literature and many public gardens. In the collections at Meadowlark, horticultural selections are used only in the VNT. This is an intentional departure from the relatively strict dictum of using regional genotypes in the PVC and VNW. This specific strategy is designed to interest ornamental gardeners in native species through the initial use of horticultural selections. The vast majority of native plants in the American nursery trade are selections. Thus, most amateur gardeners are using these horticultural creations without realizing the wild ancestor may be in need of conservation.

Ultimately, we hope to encourage use of native plants in the landscape and educate the public about the often-subtle differences between native species that represent wild populations and horticultural selections. Furthermore, we educate the visiting public and avocation gardeners alike about the ecological and conservation value of native plants in public garden collections and in the landscape at large. Through this decidedly didactic approach, we have created a forum based on living collections that promotes the International Agenda and fosters an appreciation for conserving plant diversity to a wider audience.