CPC Plant Profile: White-bract Boneset
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Plant Profile

White-bract Boneset (Eupatorium leucolepis var. novae-angliae)

Growing from 40 cm to 1 meter tall, this member of the Aster family produces typical composite flowers between July and mid-September. Photo Credit: William Larkin
Description
  • Global Rank: T1 - Critically Imperiled
  • Legal Status: N/A
  • Family: Asteraceae
  • State: MA, NY, RI
  • Nature Serve ID: 131249
  • Date Inducted in National Collection: 05/01/1999

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. Plant Description: 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.).

Participating Institutions
Updates
  • 09/11/2020
  • Propagation Research

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.

  • 09/11/2020
  • Seed Collection

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.

  • 09/11/2020
  • Reproductive Research

Dr. Kamal Bawa (University of Massachusetts, Boston, Department of Biology) has studied the reproductive ecology of Eupatorium leucolepis var. novae-angliae. 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.

Nature Serve Biotics
  • 05/02/2017

Eupatorium leucolepis var. novae-angliae is a distinct taxon endemic to Massachusetts and Rhode Island. Fifteen element occurrences are known, but it is abundant at only 3 sites. It is threatened by development, water table draw-down, off-the-road vehicle traffic and, at one site, grazing by Canada geese. The species itself is widespread on the southeast coastal plain.

Elizabeth J. Farnsworth
  • 01/01/2010

As articulated by Elliman (2001) and NatureServe (2001): 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

Elizabeth J. Farnsworth
  • 01/01/2010

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).

Elizabeth J. Farnsworth
  • 01/01/2010

Dr. Kamal Bawa (University of Massachusetts, Boston, Department of Biology) has studied the reproductive ecology of Eupatorium leucolepis var. novae-angliae. 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.

Elizabeth J. Farnsworth
  • 01/01/2010

Volunteer task forces of the New England Plant Conservation Program, New England Wild Flower Society (Framingham, Massachusetts) regularly monitor populations of Eupatorium leucolepis var. novae-angliae in New England.

Elizabeth J. Farnsworth
  • 01/01/2010

Studies of the prevalence of herbivory and its impacts on plant fitness at all sites 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

Elizabeth J. Farnsworth
  • 01/01/2010

Ex situ germination techniques are relatively well-known for this taxon.

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Photos
Nomenclature
Taxon Eupatorium leucolepis var. novae-angliae
Authority Fernald
Family Asteraceae
CPC Number 1854
ITIS 528112
USDA EUNO
Common Names justiceweed | New England boneset | New England white-bracted thoroughwort | white-bracted boneset
Associated Scientific Names Eupatorium leucolepis var. novae-angliae | Eupatorium leucolepis | Eupatorium novae-angliae
Distribution Eupatorium leucolepis var. novae-angliae is known only from Plymouth, Kingston, Lakeville, and Sandwich, Massachusetts and Jamestown and South Kingstown in Rhode Island. Once thought to be present in
State Rank
State State Rank
Massachusetts S1
New York SU
Rhode Island S1
Habitat

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).

Ecological Relationships

Eupatorium leucolepis var. novae-angliae reproduces solely by asexual means: through clonal growth via rhizomes and through the production of embryos and seeds via agamospermy, in which a diploid embryo develops by the somatic division of cells rather than by pollination (Sullivan 1992). 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).

Pollinators
Common Name Name in Text Association Type Source InteractionID

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