Spiraea virginiana

A clonal shrub often occurring in dense clumps. Stems are sparsely branched and are upright up to 1.2 m or arching with some stems touching the ground. The leaves are alternate, simple, and have variable serration. The cream-colored flowers are in showy corymbs.

Spiraea virginiana is distinguished from most other Spiraea by its creamy white flowers in corymbs, and its leaves which have an acute apex (Weakley 2004). The exotic Spiraea japonica, which also occurs along streams, has pink flowers and leaves with long-acuminate tips (Patrick et al. 1995). Spiraea virginiana closely resembles Spiraea betulifolia var. corymbosa (Ogle 1991). Spiraea virginiana is distinguished from Spiraea betulifolia var. corymbosa by its leaves which are more than twice as long as wide (as opposed to less than twice as long as wide in S. b. var. corymbosa) and cuneate base (as opposed to rounded base) (Weakley 2004). For a technical description see Gleason and Cronquist (1991) and Weakley (2004).

This species occurs on periodically flood-scoured banks of high-gradient mountain streams, meander scrolls, point bars, natural levees, and braided features of lower stream reaches, and occasionally near disturbed rights-of-way (Ogle 1992). Plants are often found on geologically active areas with erosion, deposition, and slumping, along rivers with dynamic flooding regimes, sandbars, scoured river shore and flatrock habitat with crevices. These areas also are associated with cobbles, boulders, and massive rock outcrops with sandy or clay soils and can be periodically xeric. Plants are often seen in silt, mud, and sand.

In Georgia, occurrences of Spiraea virginiana are in cracks in shelving sandstone bedrock along fast flowing creeks. Associated species include Alnus, Boykinia, Cephalanthus, Cornus amomum, Oxypolis rigidior, Viburnum cassinoides, and Xanthorhiza simplicissima.

In Ohio, occurrences of Spiraea virginiana are along slow moving streams with sandstone bedrock that are scoured during flooding, gravel bars with riparian debris. Associated with Acer saccharum, Aconitum uncinatum, Alnus serrulata, Amphicarpaea bracteata, Betula nigra, Boehmeria cylindrica, Campsis radicans, Carpinus carolinia, Cephalanthus occidentalis, Fimbristylis autumnalis, Fraxinus pennsylvanica, Glyceria striata, Onoclea sensibilis, Osmunda regalis, Pilea pumila, Polygonum amphibium, Platanus occidentalis, Saururus cernuus, Tilia americana, Toxicodendron radicans, Ulmus americana, Ulmus rubra, and Vitis riparia.

In North Carolina, Spiraea virginiana occurs along rocky bars at river edges. It grows between boulders and in fine alluvial sand and other alluvial deposits. These sites are seasonally saturated. Associated plants include Alnus serrulata, Clematis viorna, Cornus amomum, Impatiens capensis, Parthenocissus, Physocarpus opulifolius, Platanus, Rubus, Salix, Sambucus canadensis, Saponaria, Smilax, Solidago, Toxicodendron radicans, and Verbesina alternifolia.

In Tennessee, this species occurs along creek edges with margins of exposed rock and piled detritus, bars of gravel, rubble and/or boulders and including dolomitic limestone. It occurs in alluvial silt collected within cracks in the bedrock. These sites experience a regime of periodic flooding. Elevations range from 850-1420 ft. Associated species include Acer pensylvanicum, Alnus, Arisaema dracontium, Arundinaria gigantea, Conradina verticillata, Dirca palustris, Ilex verticillata, Juniperus virginiana, Liriodendron tulipifera, Orontium aquaticum, Osmunda regalis, O. cinnamomea, Phlox amoena, Salix, Senecio aureus, Silene virginica, Spiraea japonica, Toxicodendron radicans, Trautvetteria, Tsuga, Ulmus, and Viburnum dentatum.

In Virginia, occurrences of Spiraea virginiana are along flood scour zones in crevices of sandstone cobbles, boulders, and massive rock outcrop, and quartzite/feldspar boulders. Soils are sandy, silty, or clay. The elevation range is 1000-2400 ft. Associated plants include Alnus serrulata, Amphicarpaea bracteata, Betula lenta, Betula nigra, Campsis radicans, Carpinus, Cephalanthus, Cornus amomum, Dirca, Equisetum hyemale, Fraxinus, Ilex verticillata, Lobelia cardinalis, Osmunda regalis, Physocarpus, Platanus occidentalis, Polygonum punctatum, Spiraea japonica, S. tomentosa, Toxicodendron radicans, Tradescantia ohiensis, Tsuga, Verbesina alternifolia, and Xanthorhiza.

In West Virginia, occurrences are among large boulders, flatrock, and flood debris along scoured stream-sides. Soils are silt and sand. The elevation ranges from 1000-1800 ft. Associated species are Acer rubrum, Alnus serrulata, Betula nigra, Cephalanthus occidentalis, Cornus amomum, Dirca, Ilex verticillata, Osmunda regalis, Parthenocissus, Physocarpus, Platanus, Spiraea japonica, Toxicodendron radicans, Tradescantia ohiensis, Tsuga, and Xanthorhiza.

Although this element may flower profusely, it is clonal and almost exclusively reproduces vegetatively. Sexual reproduction will occur when genets are placed in close proximity but is rare in the native habitat (D.W. Ogle, pers. comm., 1996). Dispersal of seeds is by wind or water and requires a flooding regime (Brzyski and Cullen 2011). While clonal reproduction appears to be the primary mode, there is evidence that sexual reproduction takes place in some populations (Brzyski and Cullen 2001).