Furbish Lousewort

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Furbish Lousewort

Pedicularis furbishiae

ListedApril 26, 1978
FamilyScrophulariaceae (Snapdragon)
DescriptionPerennial herb with deeply serrated, frond-like leaves and greenish-yellow flowers.
HabitatRiparian; well-drained sandy loam.
ThreatsProposed reservoir impoundments.
RangeMaine; Canada (New Brunswick)


Furbish lousewort, Pedicularis furbishiae, is a perennial herb with lance-shaped, deeply serrated leaves that somewhat resemble fern fronds. Leaves are arranged alternately along a purple stalk that is 16-40 in (40-102 cm) tall. The flower is formed of a calyx with five unequal lobes and a greenish-yellow, two-lipped corolla. The upper lip is straight and lacks the conspicuous beak typical of other louseworts. Flowers are clustered in a terminal raceme and bloom from mid-July to mid-August. Fruits are round capsules protruding slightly from the calyx that disperse seeds in early September. This plant is also commonly known as St. John River wood-betony.


Furbish lousewort prefers well-drained, sandy loams that are generally low in nitrogen and high in calcium. It grows in partial sunlight. Most known lousewort stands are on north-facing river banks. The vegetation along the banks in most places is very dense, but lousewort seedlings are more abundant where vegetation is sparse.


Furbish lousewort is endemic to the St. John River Valley of northern Maine and western New Brunswick, Canada. The St. John River forms part of the United States-Canada border before traversing New Brunswick to empty into the Bay of Fundy at Saint John.

Until 1976 when seven stands were discovered along the St. John River in Aroostock County, Maine, furbish lousewort was thought to be extinct. Since that time, additional populations have been found along about 140 mi (225 km) of the river from the confluence of the Big Black River to the town of Andover, New Brunswick. The total population in 1985 was estimated at 5,000 individual plants. Because the river flow constantly changes, the populations must be large enough to withstand years of high mortality, such as in 1984 when mortality hit 75% and three colonies were extirpated due to ice. Without a complete survey, it is not possible to estimate the population in any given year.


Furbish lousewort is completely restricted to the shore of the St. John River, and even within this range, suitable habitat is limited. The water cycle of the river continually changes, and in the process destroys some lousewort populations while creating new suitable habitat.

Human activity has also altered the habitat. (One historical lousewort site is now a swimming and picnicking area.) Agricultural and residential development have destroyed the tree canopy in the downriver two-thirds of the plant's range, where it has become most scarce. Although the lousewort can survive on river banks that are too steep for agricultural fields or housing, people are clearing the riverbank trees in order to open up views of the water. At least three populations have been damaged by clearing for scenic views. Clearing land and timber harvesting have also affected the lousewort because of surface drainage that has altered the flow and depth of the river which, in turn, increases disturbance of the river banks. The quality of the river water may also affect the lousewort: populations upstream are much healthier than downstream populations.

Construction of various proposed hydroelectric projects along the St. John River have from time to time threatened furbish lousewort's habitat. In 1981 Congress denied authority for one projectthe Dickey Dambut other feasibility studies for dams have been proposed from time to time. Dam projects are contingent on approval by the U. S. Army Corps of Engineers, which is required by law to consult with the U. S. Fish and Wildlife Service (FWS) concerning threats to the lousewort.

Conservation and Recovery

The Recovery Plan prepared by the FWS recommends maintaining the integrity of the riverbank ecosystem, as well as acquiring and preserving specific population sites. There is also need for a public education program explaining the desirability of preserving the lousewort and its habitat. Botanists will attempt to establish new stands of the plant at suitable sites along the river. To protect the scenic beauty of the river, local residents banded together to prohibit further commercial or residential development from the Baker Branch Bridge to the foot of Big Rapids at Allagash, Maine.

The Canadian Committee on the Status of Endangered Wildlife and the provincial authorities in New Brunswick have placed the furbish lousewort on their respective lists of endangered wildlife.


Regional Office of Endangered Species
U.S. Fish and Wildlife Service
300 Westgate Center Dr.
Hadley, Massachusetts 01035


Macior, L. W. 1980. "Population Ecology of the Furbish Lousewort, Pedicularis furbishiae S. Wats." Rhodora 82:105-111.

Richards, C. D. 1978. "Report on Survey of the St.John River, Maine, and Some of Its Major Tributaries for Furbish's Lousewort and Josselyn's Sedge." Environmental Impact Statement, Dickey-Lincoln School Lakes Project, U.S. Army Corps of Engineers.

U.S. Fish and Wildlife Service. 1983. "The Furbish Lousewort Recovery Plan." U.S. Fish and Wild-life Service, Newton Corner, Massachusetts.