Eupatorium leucolepis var. novae-angliae
|justiceweed, New England boneset, New England white-bracted thoroughwort, white-bracted boneset|
|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 Eupatorium leucolepis var. novae-angliae is fully sponsored.
Elizabeth J. Farnsworth contributed to this Plant Profile.
Eupatorium leucolepis var. novae-angliae is a member of the daisy family (Asteraceae) and endemic to southeastern New England. Only sixteen populations are left in four counties of Massachusetts and Rhode Island. The taxon occurs almost exclusively in coastal plain ponds -- unique habitats in which water levels, fed by groundwater, fluctuate greatly from year to year. Plant population numbers track these fluctuations, with many plants appearing when water levels are low. Eupatorium leucolepis var. novae-angliae is a member of a specialized guild of rare plant species that are restricted to coastal plain ponds where they are not out-competed by other vegetation. Reasons for its increasing rarity include an apparent loss of sexual reproduction due to male sterility in the variety, as well as factors that negatively influence the water quantity and quality of coastal plain ponds (especially development with attendant water withdrawal and diversion). Off-road vehicles, excessive public use of pond beaches, and trash dumping are also cited as a common threat.
Research and Management Summary:
A handful of individuals and institutions have researched this particular species, as well as a few closely related species. The New England Wild Flower Society regularly monitors populations of this species in New England.
Eupatorium leucolepis var. novae-angliae is a robust plant, growing from a stout rhizome to between 40 cm and 1 meter in height. In July to mid-September, it bears white, composite flowers typical of the Aster family, with three to seven flowers in each head. Leaves are opposite on the hairy stem, and are fuzzy, lance-shaped, sharply toothed, tapering, and 3-8 cm long (these leaf characters distinguish this variety from its conspecific relative, Eupatorium leucolepis var. leucolepis. The plant can form dense colonies by proliferating on rhizomes, and this is its main mode of reproduction; however, it can form seeds asexually through agamospermy (Fernald 1950, Massachusetts Natural Heritage and Endangered Species Program 1986, DiGregorio 1991, Gleason and Cronquist 1991, Elliman in prep.).
Distribution & Occurrence
- New York
- Rhode Island
Fifteen of the sixteen extant populations in Massachusetts and Rhode Island occur on the upper margins of sandy to peaty shores of coastal plain ponds (MANHESP 1986, Elliman 2001). The plants typically grow in full sun or partial shade. One population in Rhode Island grows in a boggy meadow along the margin of a shrub thicket (Elliman 2001.). Coastal plain ponds in southern New England are relatively nutrient-poor habitats formed by glacial action on the coastal plain. Water levels in the ponds fluctuates markedly seasonally and from year to year, tied to groundwater level and rainfall. Few plant species can withstand this challenging cycle of inundation and drought. Eupatorium leucolepis var. novae-angliae can go dormant during years when water levels are high, relying on reserved from its starchy rhizomes. When water levels drop, the plant reappears, along with other rare coastal plain plant species.
If the magnitude of these water fluctuations diminishes due to diversion or pumping of groundwater, or if nutrients are loaded into the pond from septic leaching and surface run-off, other plant species can gain a foothold in these ponds and readily outcompete these rare specialists.
Plants associated with the taxon at various sites include an array typical of coastal plain ponds: Acer rubrum, Agalinis paupercula, Agrostis sp., Alnus serrulata, Aster lateriflorus, Betula populifolia, Bidens sp., Calamagrostis canadensis, Cladium mariscoides, Coreopsis rosea, Cyperus dentatus, Drosera filiformis, Eriocaulon aquaticum, Euthamia tenuifolia, Fuirena pumila, Gratiola aurea, Hypericum sp., Iris versicolor, Juncus canadensis, Juncus greenei, Juncus pelocarpus, Lycopus sp., Lyonia ligustrina, Lysimachia terrestris, Myrica pensylvanica, Pinus rigida, Rhexia virginica, Rhyncospora capitellata, Rumex sp., Sabatia kennedyana, Sagittaria teres, Salix sp., Scirpus americanus, Spiraea latifolia, Spiraea tomentosa, Stachys hyssopifolia, Vaccinium corymbosum, Viola lanceolata, and Xyris sp. (Elliman 2001).
|Sixteen extant element occurrences are known, all with extremely variable population numbers year to year (Sorrie 1981, Enser 2000, Elliman in prep.). The highest total population estimates (taken from populations recorded on dry years) indicate that as many as 20,000 plants may appear when conditions are optimal. However, many populations have dropped to low numbers (especially during high-water years), and the New England-wide population count can go as low as several hundred to a few thousand plants (Sorrie 1981).|
Conservation, Ecology & Research
Flowering occurs between July and September, and many insects visit the flowers, including bees, butterflies, and flies (Bawa 1989).
The single-seeded fruits are dispersed by wind in late fall (Elliman 2001).
Seed germination occurs in years in which water levels are low in coastal plain ponds. During wetter years, seeds and rhizomes enter dormancy, and the taxon appears capable of flexibly seed-banking or germinating upon dispersal (Brumback 1989).
Inbreeding depression of small populations due to erosion of genetic heterogeneity because of male sterility
Rapidly accelerating development adjacent to pond shores that permanently draws d
A rare and a common species of Eupatorium were systematically compared in terms of reproductive ecology to determine reasons for rarity (Byers 1995, Byers 1997); these studies could inform hypotheses about causes of rarity in Eupatorium leucolepis var. novae-angliae.
Remaining research has focused on population censusing for multiple years by various individuals and agencies in Massachusetts and Rhode Island.
The New England Wild Flower Society (Framingham, Massachusetts) collected seeds in September 1984, and determined that a period of moist, cold pre-treatment enhanced germination the following April (Brumback 1989). They observed that fresh seeds are also able to germinate without pre-treatment. Seeds held in storage for six years remained viable. Cuttings may also be propagated easily.
Studies of the effects of increasing nutrient loading on the coastal plain flora
Genetic studies to determine levels of genetic variation in populations
Identification of optimal environmental factors promoting seedling establishment at new or restored sites
Taxonomic studies to determine whether Eupatorium leucolepis var. novae-angliae is a distinct species and warrants promotion from a variety
Yearly monitoring of plant numbers and reproductive output for at least a decade to inform population viability analysis
George, G.G. 1992. A sysnonymized checklist of the plants found growing in Rhode Island. Peace Dale, Rhode Island: Rhode Island Wild Plant Society.
Gould, L.L.; Enser, R.W.; Champlin, R.L.; Stuckey, I.H. 1998. Vascular flora of Rhode Island: a list of native and naturalized plants. Volume 1. Kingstown, Rhode Island: Biota of Rhode Island Project, Rhode Island Natural History Survey.
Sorrie, B.A.; Somers, P. 1999. The vascular plants of Massachusetts: a county checklist. Westborough, Massachusetts: Massachusetts Natural Heritage and Endangered Species Program.