Meadowlark Botanical Gardens
Abridged from Wildflower 18 (3) 2002
At the highest elevation, red spruce Picea rubens forms conspicuous stands. Also found in these highlands in limited numbers are balsam fir Abies balsamea, red pine Pinus resinosa. At slightly lower elevations, several northern hardwoods grow. In these locations, yellow birch Betula alleghaniensis, sugar maple Acer saccharum and American beech Fagus grandifolia are frequent. Common associates of this forest include eastern hemlock Tsuga canadensis, basswood Tilia americana, black ash Fraxinus nigra paper birch B. papyrifera and scattered populations of mountain ash Sorbus americana. Common shrubs present in the northern hardwood forest are rhododendron Rhododendron maximum and mountain laurel Kalmia latifolia. The dwarf dogwood Cornus canadensis grows in scattered populations. In addition, hobblerod Vibirnum lantanoides and mountain holly Ilex montana are present.
Large varieties of herbaceous plants grow in these communities. Reflecting the northern affinity of the flora are buckbean Menyanthes trifoliata cottongrass Eriophorum virginicum and cranberry Vaccinum macrocarpon. Several orchids also grow here, including the beardflower Pogonia ophioglossoides, purple-fringed orchid Habenaria fimbriata, yellow-fringed orchid H. ciliaris and grasspink Calopogon tuberosus. Within the northern hardwoods, herbaceous plant can include hellebore Veratrum viride, painted trillium Trillium undulatum, Fraser’s sedge Cymophyllus fraser, shining clubmoss Huperzia lucidulum, spinulose shield fern Dryopteris spinulosa, oak fern Gymnocarpium dryopteris and goldthread Coptis groenlandica. Several of these species also grow further east on the highest peaks in Shenandoah National Park.
Cove Hardwoods
Several locations in the western Piedmont and mountains contain cove hardwood communities. This vegetation often occupies deep hollows adjacent to steep slopes. Soil is normally rich in organic matter and high in moisture. These communities exist in Shenandoah National Park, George Washington National Forest and the Monongahela National Forest. Several trees attain their best development in this community. Common species include yellow poplar Liriodendron tulipifera, red oak Quercus rubra, white oak Q. alba, black walnut Juglans nigra, black birch Betula lenta, sweet buckeye Aesculus octandra, shagbark hickory Carya ovata, bitternut hickory C. cordiformis, white ash Fraxinus americana, cucumber tree Magnolia acuminata and eastern hemlock Tsuga canadensis. The later is now in severe decline do to the invasive scale insect wholly adelgid.
A diverse selection of middle and lower canopy trees grow in the cove hardwood community. Predictably, the dogwood Cornus florida is prominent among these. In addition, umbrella magnolia M. tripetala, sourwood Oxydendron arboreum, holly Ilex opaca, redbud Cercis canadensis, striped maple Acer pensylvanicum, serviceberry Amelanchier arborea and witch hazel Hamamelis virginiana can be locally abundant. Numerous shrubs find suitable habitat in the cove hardwood community. Growing with regularity are alternate-leaved dogwood C. alternifolia, Leatherwood Dirca palustris Hercules’ club Aralia spinosa and the parasitic buffalo-nut Pyrularia pubera.During the early spring this community renders an array of wildflowers. Taking advantage of increased temperatures and rich soils, numerous spring flowers begin their rapid reproductive process. Several members of the lily family are abundant. Large-flowered trillium Trillium grandiflorum, purple trillium T. erectum, white trout lily Erythronium albidum, white wood lily Clintonia umbellata, Indian cucumber Medeola virginiana, large-flowered bellwort Uvularia grandiflora, and false Solomon’s seal Smilacina racemosa are common. Orchids also grow here, the yellow lady’s slipper Cypripedium calceolus occur randomly. The showy lady’s slipper Cypripedium reginae, is restricted to a few locations in the watershed including some cove hardwood communities.
Shale Barrens
Located primarily in the central Potomac Valley, shale barrens make up a modest portion of the watershed’s flora. These communities exist mainly in the Valley and Ridge province of West Virginia’s eastern panhandle and adjacent counties in Maryland and Virginia. A particularly well-developed shale barren is in the Sideling Hill Creek watershed located in western Maryland. Plants that occupy these small areas are often rare, and some are endangered. The shale barren community has been the subject of several detailed studies. Situated on exposed south-facing terraces of Devonian shale, these areas retain water briefly and endure sunny conditions. These conditions have fostered the evolution of several endemic species. Generally, shale barrens have few tree species. Those that do occur on the loose substrate are often stunted. These species are often limited to scrub pine Pinus virginiana, dwarf hackberry Celtis tenuifolia, table mountain pine Pinus pungens and scrub oak Quercus ilicifolia.
Herbaceous plants include a number of endemic species. These include Kate’s Mountain clover Trifolium virginicum, mountain pimpernel Pseudotaenidia montana, shale onion Allium cernuum, shale evening-primrose Oenothera argillicola, shale bindweed Calystegia spithamaea, Virginia pussytoes Antennaria neglecta var.argillicola, shale leatherflower Clematis albicoma, shale ragwort Senecio antennariifolius and yellow buckwheat Eriogonum allenii. A number of additional species occur in the shale barren community that are not exclusive to it.
Limestone Communities
Two major limestone formations occur in the Potomac Valley. The largest neatly forms the linear base of the Shenandoah Valley. The other somewhat smaller formation out-crops near the mountain-piedmont boundary south of Frederick, Maryland. Another formation forms small cliffs near Franklin, West Virginia. Characteristic trees of this community are chinquapin oak Quercus muhlenbergii, hackberry Celtis occidentalis and butternut Juglans cinerea. A common shrub of this community is wild hydrangea Hydrangea arborescens.
Perhaps herbaceous plants illustrate the best representation of this community. Several lime-dwelling ferns are noted. These species frequently grow on cliffs and ledges. Walking fern Asplenium rhizophyllum, black spleenwort A. resiliens, bulblet fern Cystopteris bulbifera and purple cliffbrake Pellaea atropurpurea can be abundant. A rare hybrid found in these areas is a cross between the ebony spleenwort A. platyneuron and walking fern. The result is Scott’s spleenwort A. x ebenoides, a unique fern that combines variable morphologic characteristics of both parents.
Beyond the ferns, many other species of calcareous habitat grow here. Cliff green Pachistima canbyi, is notable for its limited distribution and cliff dwelling habitat. Other species associated with limestone formations include glaucous stonecrop Sedum glaucophyllum, false pennyroyal Trichostema brachiatum, blazing star Liatris spp., lime dwelling prickly-pear Opuntia humifusa var. humifusa, herb Robert Geranium robertianum and the rare sedge Carex eburnea, found only at Smoke Hole Cavern, West Virginia.
River Terrace and Floodplain Forest
Situated along alluvial terraces of the Potomac, this forest contains numerous species of mesic and hydric soils. The composition and distribution of this community is due in large part by the variable hydrology of the Potomac. Floods are common during the late winter, spring and during summer thunderstorms.
Several lower canopy trees and shrubs are common members of the river-terrace community. Hackberry Celtis occidentalis, American hornbeam Carpinus caroliniana and hop hornbeam Ostyra virginiana are frequent on alluvial soils. Growing in local abundance, pawpaw Asimina triloba is notable for its edible fruit. Pawpaw is the northernmost member of the largely tropical Annonaceae family. Several other shrubs are prolific members of this community: bladdernut Staphylea trifolia, spicebush Lindera benzoin, silky dogwood Cornus ammomum and winterberry Ilex verticillata, among others.
Herbaceous growth in the river-terrace forest is notable for its wildflowers. Each spring, ephemeral colonies of various flowers blanket the forest floor. Bluebells Mertensia virginica,Trillium sessile, trout lily Erythronium canadensis, dutchman’s breeches Dicentra cucullaria, cut-leaved toothwart Dentaria laciniata and fringed phacelia Phacelia prushii bloom in the sun’s warmth before the tree foliage matures. Slightly later in spring, the herbs continue to proliferate in the increasing warmth and shade. Notable among the late spring flowers are jack-in-the-pulpit Arisaema triphyllum, wild blue phlox Phlox divaricata, wild geranium Geranium maculatum, marsh marigold Caltha palustris and golden ragwort Senecio aureus. By late summer and fall, the blooms of monkey flower Mimulus ringens, cardinal flower Lobelia cardinalis, blue lobelia L. siphilitica, turtlehead Chelone glabra and many composites are abundant in the river-terrace community.
Oak-Hickory Woodlands
This community constitutes the largest single forest type in the Potomac Valley. Expanding from the western Coastal Plain to the Allegheny Plateau, oak-hickory woodlands dominate well-drained soils of the Piedmont Province and Blue Ridge Mountains. Excellent examples of the community are in the George Washington National Forest and Shenandoah National Park. Chestnut oak Quercus montana, white oak Q. alba and red oak Q. rubra are common. Chestnut oak is most abundant on the drier, often rocky sites. Growing in less abundance is black oak Q. velutina. Ranging widely among the oaks on sites with slightly higher soil moisture is mockernut hickory Carya tomentosa. Found randomly through this forest is black gum Nyssa sylvatica; know for it’s crimson fall foliage. Found commonly on soils with higher moisture content is yellow poplar Liriodendron tulipifera and red maple Acer rubrum. Growing in local abundance around stream margins are American beech Fagus grandifolia and American hornbeam Carpinus caroliniana. In steep rocky areas or on outcrops Virginia pine Pinus virginiana, pitch pine Pinus ridgida and red cedar Juniperus virginiana can be abundant.
Among the lower canopy, several shrubs and trees grow in varying abundance. Common throughout is the flowering dogwood Cornus florida. The fall flowering witch hazel Hamamelis virginiana, often forms beautiful stands along stream margins. In addition, serviceberry Amelanchier arborea, fringetree Chionanthus virginicus, American holly Ilex opaca and sassafras Sassafras albidum are also abundant. Redbud Cercis canadensis is very common. Found growing on damp soils is Virginia magnolia Magnolia virginiana. Wafer ash Ptelea trifoliata, one of only two genera in the orange family found in the Potomac Valley, grows in limited numbers in the western piedmont.
A diversity of native viburnums occurs in this forest, including maple-leaved viburnum Viburnum acerifolium, black haw V. prunifolium, naked with-rod V. nudum and roughish arrowwood V. dentatum. Strawberry bush Euonymus americanus can be abundant in some locations. Many vines grow in the Oak-Hickory woodlands. Prominent among these are Virginia creeper Parthenocissus quinquefolia, fox grape Vitis labrusca, sawbrier Smilax glauca, common greenbrier S. rotundifolia, hispid greenbrier S. hispida, poison ivy Toxicodendron radicans and wild potato vine Ipomoea pandurata.
The heath family contributes many shrubs. Dominant throughout the area, many genera of this family are integral components of the flora. Deerberry Vaccinium stamineum and lowbush blueberry V. pallidum are prominent. A larger relative present only in moist soils is highbush blueberry V. corymbosum. Two members of a closely related genus, dangleberry Gaylussacia frondosa is primarily a Coastal Plain species, while black huckleberry G. baccata is very widespread. Another widespread heath, maleberry Lyonia ligustrina, prefers damp soils. Staggerbush L. mariana grows mainly in the eastern Piedmont and Coastal Plain. Mountain laurel Kalmia latifolia is common and often forms large colonies in Oak-Hickory woodlands. Three species of rhododendron grow in this forest, only two of which have a wide distribution. Specimens of great rhododendron Rhododendron maximum are found in limited numbers in the east but become much more abundant toward the Blue Ridge. Alternatively, in suitable soil types, pinxter flower R. nudiflorum and swamp azalea R. viscosum are abundant. Having a relatively limited distribution in the Potomac Piedmont, fetterbush Leucothoe racemosa is restricted to wet sites.
The distribution of pteridophytes is affected to some degree by soil conditions. An exception, the cosmopolitan bracken fern Pteridium aquilinum var. latiusculum grows in many locations, often forming large colonies. In wetter soils, sensitive fern Onoclea sensibilis, New York fern Thelypteris noveboracensis, hay-scented fern Dennstaedtia punctiloba, cut-leaved grape fern Botrychium dissectum and rattlesnake fern B. virginianum occur in varying numbers.
Found in various locations with nutrient soils are large and small colonies of clubmosses. Tree clubmoss Lycopodium obscurum, shining clubmoss Huperzia lucidulum and crows feet Lycopodium digitatum can be quite common. Clubmosses are highly sensitive to soil disturbance and large colonies are often lost to development. Great Falls National Park in northern Virginia has several expansive clubmoss colonies.
Oak Hickory forests grade into the Coastal Plain beyond the Fall Line near Washington, DC. Many species of Coastal Plain distribution reach the fresh water tributaries of the lower Potomac Watershed. Perhaps most notable are the trees, loblolly pine Pinus taeda and sweetgum Liquidamber styracifula. Bald cypress Taxodium distichum reaches the Potomac watershed in King George County, Virginia. Wax-myrtle Myrica cerifera, a small tree with fragrant foliage, also grows in the lower Potomac Watershed. Brackish water occurs in the Potomac near Quantico, Virginia. While the Potomac Valley collection does not seek to include halophytic plants of the river in this area, many coastal plain species represent desirable accessions.
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