About the Native Arboretum
The Native Arboretum project is located at the Marie Butler Leven Preserve, in the McLean section of Fairfax County. The project began in 2004, and is based on an agreement between the Fairfax County Park Authority, which owns the Preserve, and the Earth Sangha. The aim of the project is to transform the Preserve into an extensive collection of plants native to the greater Washington, DC, region. The collection will not include every native species, but it will represent the full spectrum of the region’s flora—trees, shrubs, vines, and herbs (nonwoody plants).
The Marie Butler Leven Preserve lies along Kirby Road (Route 695), less than half a mile north of the intersection with Chesterbrook Road (Route 689). (For a location map and driving directions, see the Volunteering or Visiting page.)
The Preserve covers about 20 acres. Roughly three-quarters of the area is forested; the rest is lawn and field. There is a small parking lot and one house on the property. The stone and cinderblock ruins of a barn can be found in the woods near the main lawn. The foundation of an old spring-house is visible in the little gorge that runs through the Preserve’s eastern forest and empties into a small seasonal pond, also within the Preserve’s forest. Perhaps the most remarkable natural feature of the Preserve is the spring source near the top of that gorge; relatively few streams in Fairfax County originate on parkland.
There are several trails through the Preserve’s forest, and visitors can see a variety of naturally-occurring native plants on the grounds. (“Naturally occurring,” in this context, means that we didn’t plant them in.) Among the notable trees: A very large black cherry (Prunus serotina), a colony of sweetbay magnolia (Magnolia virginiana), a handsome patch of pawpaw (Asimina triloba), and several large American basswoods (Tilia americana). There was also a big stump-sprout of American chestnut (Castanea dentata) along the trail that loops around the pond. Unfortunately, that stem has now been killed by the chestnut blight, but other sprouts are likely to emerge from this old chestnut rootstock. Among the Preserve’s native shrubs is a large clump of blackhaw (Viburnum prunifolium), our largest native viburnum. Among the herbs of the forest floor, there are three species of trillium (Trillium grandiflorum, T. erectum var. erectum, and T. luteum), Jack-in-the pulpit (Arisaema triphyllum), squirrel corn (Dicentra canadensis), and wild blue phlox (Phlox divaricata). To see some of these plants, view the Native Arboretum Native Plants slide show.
But the Preserve’s native flora is seriously threatened by invasive alien plants. When the Native Arboretum project started, large parts of the forest floor were covered with a dense invasive groundlayer of, for example, common periwinkle (Vinca minor), English ivy (Hedera helix), wintercreeper euonymus (Euonymus fortunei), and Japanese pachysandra (Pachysandra terminalis). The forest understory consisted mostly of invasive shrubs, such as multiflora rose (Rosa multiflora) and winged burningbush (Euonymus alatus). And much of the forest edge was choked with the invasive vines Asiatic tearthumb (Polygonum perfoliatum), porcelainberry (Ampelopsis brevipedunculata), oriental bittersweet (Celastrus orbiculatus), and Japanese honeysuckle (Lonicera japonica). These and other invasives had displaced native groundlayer and understory throughout much of the Preserve’s forest.
The invasives were also threatening the forest canopy. Some invasive trees, such as paper mulberry (Broussonetia papyrifera) and white mulberry (Morus alba), were displacing native trees in certain areas. A more pervasive threat to the canopy resulted from the invasive vines that had climbed many of the trees, weakening them and making them more likely to topple. A longer-term threat was presented by the invasive thickets and groundcover infestations, which interfere with forest regeneration by making it difficult for tree seeds to sprout, or by suppressing the relatively few tree seedlings that do emerge. When our project started, the Preserve was well on its way from being a small but diverse native forest to becoming a large invasive thicket.
Over 30 species of seriously invasive alien plants have colonized the Preserve. Every major form is represented—trees, vines, shrubs, and herbs. (See the Native Arboretum Invasive Alien Plant List.) These infestations are not just a problem for native plants; invasive displacement of the native flora is also degrading the habitat of many native animals.
Another threat to the Preserve’s native flora is unnaturally heavy deer browsing. Deer are native to the mid-Atlantic region, but deer populations here and in much of the country are unnaturally high because of the elimination of predators and the widespread fragmentation of forest, which tends to create habitats favorable to deer. Deer browse some native plants heavily, but they avoid most of the Preserve’s invasives; this selective browsing promotes the spread of the invasives. To learn more about deer browsing pressure, read our Backgrounder on White-Tailed Deer and Our Plant Communities. Our project does not address the deer-browsing problem, but the Fairfax County Park Authority does occasionally schedule deer control (professional hunts) at the Preserve, as at many other county parks.
Where to Find More Information
The Native Arboretum project has made substantial progress in controlling invasives at the Preserve, and in reestablishing native plant communities. For a detailed description of project activities and accomplishments, see the Native Arboretum Project Modules page.
For other coverage of the Native Arboretum, take a look at the slide shows listed in the Links panel of the Native Arboretum page. For recent activities, check the Native Arboretum News.