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Spiraea virginiana by Hugh and Carol Nourse. Image may be subject to copyright.
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Spiraea virginiana Britt.

Virginia Spirea

Federal Protection: Listed Threatened

State Protection: Threatened

Global Rank: G2?

State Rank: S1

Element Locations Tracked in Biotics: Yes

SWAP High Priority Species (SGCN): Yes

Element Occurrences (EOs) in Georgia: 4

Habitat Summary for element in Georgia: Bouldery gravel bars and ledges along major streams


Description

Shrub 3 - 13 feet (1 - 4 meters) tall with erect, arching, or prostate stems forming dense thickets in riparian zones. The leaves are 1 - 2 inches (3 - 5 cm) long, alternate, lance-shaped, oval, or oblong, and taper to a short (2 - 5 mm) leaf stalk; leaf tips are rounded to pointed, always with a tiny, sharp point; leaf margins are smooth or toothed only above the middle; the upper leaf surfaces are green and hairless, the lower leaf surfaces powdery white. Flower clusters are showy, branched, rounded or flat-topped, 0.8 - 3 inches (2 - 8 cm) wide (sometimes up to 8 inches, 22 cm, wide), usually held at the tips of branches. The flowers are less than 0.24 inch (2 - 6 mm) wide, with 5 rounded, white petals surrounding a greenish-yellow disk bearing many showy stamens. Fruits are small, shiny pods borne in clusters.

Similar Species

An invasive ornamental shrub, Japanese Spiraea (Spiraea japonica), has a similar growth form but has pink flowers in flat-topped clusters, 2 - 8 inches (5 - 22 cm) wide, and leaves with long-tapering tips. It is ranked "Category 2" by the Georgia Exotic Pest Plant Council, indicating that it is an "exotic plant that is a moderate problem in Georgia natural areas through invading native plant communities and displacing native species."

Several other shrub species found along streams have white, flat-topped flower clusters, including Elderberry (Sambucus canadensis) and Wild Hydrangea (Hydrangea arborescens). Elderberry has compound leaves. Wild Hydrangea has opposite leaves.

Related Rare Species

Broadleaf Meadowsweet (Spiraea latifolia) and Hardhack (Spiraea tomentosa), both of Special Concern, are shrubs up to 6 feet (2 meters) tall. They are common northern species that reach their southern limits in bogs and wet meadows in north Georgia.

Broadleaf Meadowsweet (Spiraea latifolia) has erect, elongated flower clusters and coarsely toothed leaves. For more information, see: https://www.georgiabiodiversity.org/natels/profile?es_id=16899

Hardhack, Steeplebush (Spiraea tomentosa, Georgia Special Concern) has pink to rose-purple flowers in tight, narrow, erect clusters; its leaves are toothed, and the lower surfaces are densely covered with wooly, white or tan hairs. It was known in Georgia from a single bog in Union County but has not been seen since 1930.

Habitat

Rocky streams over sandstone, including bouldery stream banks, edges of waterfalls, and rock ledges. Plants require occasional scouring floods to reduce competition from other shrubs.

Life History

Spiraea virginiana is adapted for life in the high-disturbance zone of frequently flooded stream banks and stream beds. It reproduces vegetatively by layering, and by growth and fragmentation of underground stems (rhizomes); the fragments are swept downstream to new habitat. It also reproduces sexually; its flowers set fruit and produce seeds, but seedlings are rarely seen in the wild. Seeds are dispersed by water and possibly by wind.

Spiraea virginiana is dependent on flood-scouring of river banks and sand and cobble bars that removes competition by other shrubs and may promote seed germination – seeds grown in cultivation germinate best on bare mineral soils. If seeds are produced, they would likely be dispersed by flooding. In cultivation, seeds germinate best after a lengthy period of cold stratification, suggesting that the warmer winter temperatures predicted as a result of climate change will further depress seedling recruitment.  Spiraea virginiana flowers are self-incompatible, posing a problem for a highly clonal species with widely separated populations – low levels of genotypic diversity and absence of seedling recruitment have been found in many populations.

Spiraea virginiana is an important food for beaver (Castor canadensis) in some locations. Beaver browsing stimulates rhizome growth and may promote vegetative dispersal when freshly cut twigs are washed downstream.

Survey Recommendations

Surveys are best conducted during flowering (late May–July) and fruiting (August–October).

Range

About 30 genetically distinct populations are known in seven states: Georgia, North Carolina, Tennessee, Virginia, West Virginia, Kentucky, and Ohio; plants in Alabama and Pennsylvania have been destroyed.

Threats

Altering stream flow by damming or otherwise obstructing streams. Off-road vehicle use in stream beds and on banks. Severe flooding that washes out populations. Invasion by exotic pest plants, such as Rosa multiflora, Lonicera japonica, Ligustrum sinense, and Miscanthus sinensis. Low genetic diversity. Lack of sexual reproduction. Deer browsing. Alterations of stream flow and storm intensity related to climate change. Warming winters related to climate change.

Georgia Conservation Status

Spiraea virginiana is ranked S1 by the Georgia Department of Natural Resources, indicating that the species is critically imperiled in Georgia. It is listed as Threatened by both the State of Georgia and the U.S. Fish and Wildlife Service. Three populations have been documented in Georgia, one occurs on state park land and two are protected on private conservation lands.

Conservation Management Recommendations

Avoid changes to stream flow from damming and road construction. Prevent off-road vehicle access to streams. Reduce competing tree and shrub cover. Eradicate exotic pest plants. Reduce the size of Georgia's deer herd. Augment populations to increase genetic diversity. Address climate change. Research solutions for low seed and seedling recruitment.

References

Brzyski, J.R. and T.M. Culley. 2013. Seed germination in the riparian zone: the case of the rare shrub, Spiraea virginiana (Rosaceae). Castanea 78(2):87-94. https://doi.org/10.2179/12-039

Brzyski, J.R. and T.M. Culley. 2011. Genetic variation and clonal structure of the rare, riparian shrub Spiraea virginiana (Rosaceae). Conservation Genetics 12: 1323-1332. https://link.springer.com/article/10.1007/s10592-011-0233-x

Chafin, L.G. 2007. Field guide to the rare plants of Georgia. State Botanical Garden of Georgia and University of Georgia Press, Athens.

GADNR. 2020. Element occurrence records for Spiraea virginiana. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, Georgia.

Horton, J.L., J. McKenna, C.R. Rossell Jr., H.D. Clarke, J.R. Ward, and S.C. Patch. 2015. Habitat characteristics of Spiraea virginiana Britton, a federally threatened riparian shrub, in North Carolina. Castanea 80(2): 122-129. https://www.jstor.org/stable/24621225?seq=1#metadata_info_tab_contents

Kral, R. 1983. A report on some rare, threatened, or endangered forest-related vascular plants of the South. Technical Publication R8-TP2. United States Forest Service, Atlanta.

Lance, R. 2004. Woody plants of the southeastern United States: a winter guide. University of Georgia Press, Athens.

NatureServe. 2020. Spiraea virginiana species account. NatureServe Explorer. NatureServe, Arlington, Virginia. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.135631/Spiraea_virginiana

Ogle, D.W. Virginia spiraea, Spiraea virginiana Britton. In, K. Terwilleger. 1991. Virginia’s endangered species. Virginia Department of Game and Inland Fisheries. McDonald and Woodward Publishing Company, Blacksburg, Virginia.

Ogle, D.W. 1991. Spiraea virginiana Britton: I. delineation and distribution, II. ecology and species biology. Castanea 56: 287-303.                                                                                        https://www.jstor.org/stable/4033826?seq=1#metadata_info_tab_contents    AND https://www.jstor.org/stable/4033827?seq=1#metadata_info_tab_contents

Pate, S.J. 2010. Phylogeography and mating system of Spiraea virginiana Britton: a multi-scale exploration of the biology of a threatened species. M.S. Thesis, Appalachian State University, Boone, North Carolina. https://libres.uncg.edu/ir/asu/f/Pate,%20Sarah_2010_Thesis2.pdf

Patrick, T.S., J.R. Allison, and G.A. Krakow. 1995. Protected plants of Georgia. Georgia Department of Natural Resources, Natural Heritage Program, Social Circle.

USFWS. 2019. Virginia spiraea (Spiraea virginiana). U.S. Fish and Wildlife Service. https://ecos.fws.gov/ecp0/profile/speciesProfile?sId=1728

Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill. http://www.herbarium.unc.edu/flora.htm

Authors of Account

Linda G. Chafin

Date Compiled or Updated

L. Chafin, Aug. 2008: original account.

K. Owers, Feb. 2010: added pictures.

L. Chafin, May 2020: updated original account.

Spiraea virginiana, illustration by Jean C. Putnam hancock. Image may be subject to copyright.
Spiraea virginiana by Hugh and Carol Nourse. Image may be subject to copyright.