|Darlington's spurge, glade spurge, purple spurge|
|Elizabeth J. Farnsworth|
The following Participating Institutions are custodians for this species in the CPC National Collection:
New England Wild Flower Society
The conservation of Euphorbia purpurea is fully sponsored.
Elizabeth J. Farnsworth contributed to this Plant Profile.
This handsome, stout perennial is found in rich stream valleys of the Appalachian belt of the eastern United States from Delaware to Ohio and West Virginia. This species is rare throughout its range, and wetland alteration, grazing by deer and livestock, and trampling by recreational activity pose continual threats to it's long-term survival.
Research and Management Summary:
A number of individuals and institutions have studied this species, but very little information is available on management activities in areas where it occurs.
Growing to 1 meter (3 feet) in height, Euphorbia purpurea is named for the purplish, glandular bracts (leaves that enclose inflorescences) that are characteristic of members of its plant family. It is a perennial that forms from a thick rhizome. Its lightly fuzzy leaves are 1 to 3 cm long and occur opposite each other along the stem. Its fruits are small (6 to 8 mm long) and covered with irregular bumps.
Distribution & Occurrence
- New Jersey
- North Carolina
- West Virginia
Euphorbia purpurea tends to occur in rich, cool woods along seeps, swamps or streamside, often influenced by circumneutral bedrock such as limestone or Ordovician sandstone (Fortney 1975). The species is primarily known from the interior highlands of Maryland, North Carolina, Ohio, Pennsylvania, and the Virginias, although a few populations persist in Delaware and New Jersey (Ogle 1989, NatureServe 2001). There, the growing season is short and precipitation amounts are high relative to the lower elevation regions (Fortney 1975).
Other plant species observed in these areas include disjunct northern taxa like balsam fir (Abies balsamifera), glaucus willow (Salix sp.), Alder-leaved buckthorn (Rhamnus alnifolia), Nannyberry (Viburnum lentago), purple avens (Geum rivale) and highbush cranberry (Viburnum trilobum), trembling aspen, fire cherry, red raspberry, and swamp Saxifrage (Fortney 1975, 1993). Other associated species described from the single Ohio occurrence include bulblet fern (Cystopteris bulbifera), ginger (Asarum canadense), and goatsbeard (Aruncus dioicus), also indicative of rich soils.
NOTE: Euphorbia purpurea is considered a facultative wetland plant (USDA 2001), but Gleason and Cronquist (1991) describe the habitat as dry or moist woods.
|Euphorbia purpurea is reported from approximately 50 extant occurrences (NatureServe 2001), many with small populations. Worldwide population numbers are unknown, but probably on the order of less than 10,000 plants.|
Conservation, Ecology & Research
The plant typically flowers during May and June (Gleason and Cronquist 1991). It is capable of vegetative reproduction along a starchy rhizome.
The related Euphorbia esula (leafy spurge), a weedier species, shows ballistic seed dispersal in which seeds are thrown up to 15 feet from the plant and secondarily dispersed by water and animals (USDA 1989), but these phenomena have not been confirmed for this species.
Euphorbia purpurea appears to thrive in the dappled shade of a woodland canopy and grows best on rich, circumneutral soils (Fortney 1975).
A major threat to the species is herbivory, particularly by deer (Rhoads 2001) and groundhogs.
Another potentially threatening herbivore is the root-mining flea beetle, Aphthona flava Guill., which has been widely introduced to control leafy spurge (Pemberton 1985, USDA 1989). However, studies by APHIS at Purdue University indicate that this biocontrol agent does not host-switch (yet) to the rarer Euphorbia purpurea.
Herbivory by deer and other mammals
Habitat conversion for agriculture and residential development
Off-road vehicle use and trampling by hikers
The New England Wild Flower Society has cooperated with The Nature Conservancy Ohio Field Office (contact Larry Smith) to collect and store seed from Ohio. Some plants were propagated in 1991 and have grown well in the garden. However, cultivation from rooted cuttings and germination from seed are both very erratic and difficult to replicate. Seed cleaned and stored dry or refrigerated and sown outdoors can germinate, but results are variable.
The U. S. Fish and Wildlife Service lists Doug Ogle (Virginia Highlands Community College, Abingdon, Virginia); Ted Bradley (George Mason University, Fairfax, Virginia); Chris Ludwig (Virginia Division of Natural Heritage, Richmond); and Garrie Rouse (Rouse Environmental Services, Aylett, Virginia) as survey contacts knowledgeable about Euphorbia purpurea as of November 1999.
Studies quantifying the impact of deer grazing on Euphorbia purpurea
Long-term demographic studies to inform population viability analyses
Monitoring to document any herbivory (host-switching) on Euphorbia purpurea by newly-released biocontrol agents meant to control Euphorbia esula (leafy spurge)
Fortney, R.H. 1993. Canaan Valley: an area of special interest within the upland forest region. In: Stephenson, S.L., editor. Upland Forests of West Virginia. McClain Printing Company. Parsons, West Virginia. p 47-65.