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A small yellow flower with red markings extends from a fern-like plant.
Information icon Sensitive joint-vetch. Photo by dogtooth77, CC BY-NC-SA 2.0.

Sensitive joint-vetch

Aeschynomene virginica

Taxon: Plant
Range: Maryland, New Jersey, North Carolina, Virginia
Status: Listed as threatened on May 20, 1992

Sensitive joint-vetch gets its name from its leaves, which fold slightly when touched. According to the Five Year Review completed in 2013, only 32 occurrences remain in New Jersey, Maryland, North Carolina, and Virginia, and the species is no longer found in Pennsylvania and Delaware. Sensitive joint-vetch is easily confused with the invasive weed Aeschynomene indica, and sometimes referred to erroneously as an agricultural pest. Genetic and taxonomic studies resolved this confusion in the 1980’s and 1990’s. Major causes of decline include road construction; residential, commercial and industrial development; water pollution; bank erosion; and motor boat traffic — all habitat disturbances associated with rapid population growth.

Appearance

Sensitive joint-vetch is an annual plant in the pea family (Fabaceae) that is native to the Eastern United States. Plants typically attain heights of 3.3 to 6.6 feet in a single growing season, although they can grow as tall as 7.8 feet. The stems are single, sometimes branching near the top, with stiff or bristly hairs. The leaves are even-pinnate, 0.8 – 4.7 inches long, with entire, gland-dotted leaflets. Each leaf consists of 30 to 56 leaflets. Leaflets are 0.3 – 1 inch long and 0.08 – 0.16 inches wide. The yellow, irregular flowers are 0.4 – 0.6 inches across, streaked with red, and grow in racemes (elongated inflorescence with stalked flowers). The fruit is a loment with four to 10 one-seeded segments, turning dark brown when ripe. Fruits are 1.2 - 2.8 inches long and shallowly scalloped along one side.

A chart to help people identify sensitive joint-vetch
Sentitive joint-vetch identification chart by NC National Heritage Program, photos by Misty Buhanan, Laura Robinson, Dale Suiter..

Plants flower from July through September and occasionally into October. In autumn, senescence may be triggered by the drop in water temperature or by salinity intrusion due to a decrease in freshwater flow. Bumblebees have been observed pollinating the flowers. Fruits form shortly after the first signs of flowering in July. Although flowering continues until late fall, production of vigorous fruits appears to decline significantly by mid-October. Seed maturation begins in August and continues through October. Germination takes place from late May to early June. Seedlings grow quickly, approximately doubling in size every 2 weeks during the first 6 weeks.

This species has been confused with other members of the genus, especially A. indica and A. rudis. These two species, not native to the United States, have spread northward into North Carolina in recent years, where their ranges now overlap with that of this threatened species. A. indica is common in wet agricultural areas from Virginia to Florida, and west to Texas and north to Missouri. A. rudis has a scattered distribution from Pennsylvania to Florida to California.

Habitat

Sensitive joint-vetch typically grows in the intertidal zone of coastal marshes where plants are flooded twice daily. The species seems to prefer the marsh edge at an elevation near the upper limit of tidal fluctuation,where soils may be mucky, sandy, or gravelly. It is usually found in areas where plant diversity is high (50 species per acre) and annual species predominate. Bare to sparsely vegetated substrates appear to be of critical importance to this plant. As an annual, it requires such microhabitats to establish and grow. Such areas may include areas along rivers with new deposits of soil that have not yet been colonized by perennial species, low swales within extensive marshes, or areas where muskrats have eaten most of the vegetation. It appears to remain at a particular site for a relatively short period of time, and maintains itself by colonizing new, recently disturbed habitats where it may compete successfully among other early-successional species. It is frequently found in the estuarine meander zone of tidal rivers where sediments transported from upriver settle out and extensive marshes are formed. The substrate may be sandy, muddy, gravelly, or peaty. In North Carolina, sensitive joint-vetch is most often found in roadside ditches, often with some connection to nearby brackish marshes.

Historic range

Historically, sensitive joint-vetch was found in New Jersey, Delaware, Pennsylvania, Maryland, Virginia, and North Carolina. It has been extirpated from Delaware and Pennsylvania.

Current range

The species is known from Maryland, New Jersey, Virginia and North Carolina. The species shows considerable annual fluctuation in population numbers, varying in at least one case from approximately 50 to 2,000 individuals over a three-year period. Although populations do fluctuate, there is an apparent trend for large populations to remain large and small populations to remain small.

Conservation challenges

The extirpation of sensitive joint-vetch from Delaware and Pennsylvania and its elimination from many sites in other states can be directly attributed to habitat destruction. Many of the marshes where it occurred historically have been dredged and/or filled and the riverbanks stabilized with bulkheads or riprap. Other threats include sedimentation, competition from exotic plant species, recreational activities, agricultural activities, mining, commercial and residential development with associated pollution and sedimentation, impoundments, water withdrawal projects and introduced insect pests.

Recovery plan

Download the 1995 recovery plan.

Partnerships, research and projects

In 2013, the Service, the North Carolina Natural Heritage Program (NCNHP) and the North Carolina Albemarle Pamlico Estuary Partnership conducted surveys for sensitive joint-vetch at historic locations in North Carolina. Very few plants were found during those surveys.

How you can help

  • Conduct surveys
  • Keep an eye out for this species in roadside ditches and other appropriate habitat, especially in Hyde County, North Carolina
  • Report observations to the Service and the NCNHP

Subject matter experts

More information

References

NC Natural Heritage Program, North Carolina surveys for federally threatened Sensitive joint-vetch (Aeschynomene virginica). Final report prepared for Albemarle Pamlico National Estuary Partnership, Figure 15. Distinguishing characteristics and comparison between Aeschynomene virginica and Aeschynomene indica. October 22, 2013.

Federal Register notices

The following Federal Register documents were automatically gathered by searching the Federal Register Official API with this species’ scientific name ordered by relevance. You can conduct your own search on the Federal Register website.

  • We're sorry but an error occurred. Visit the Federal Register to conduct your own search.

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