CPC Plant Profile: Osterhout's Milkvetch
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Plant Profile

Osterhout's Milkvetch (Astragalus osterhoutii)

View of this tall plant with numerous upright stems. Photo Credit: Carol Dawson
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Fabaceae
  • State: CO
  • Nature Serve ID: 155315
  • Date Inducted in National Collection: 02/10/1987

Osterhout milkvetch grows in high-selenium soils. Selenium is concentrated in its plant tissue, producing an unpleasant odor (Dornbirer 1995). The plant is a tall, herbaceous perennial with rush-like stems. It produces numerous cream-colored flowers. A significant part of the known range and population was lost when a new reservoir was filled on the Muddy Creek in 1995. (Von Bargen 1997)

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Updates
  • 08/26/2020
  • Propagation Research

The populations surrounding Kremmling, CO have been monitored by Denver Botanic Gardens since 1993. Additionally, a habitat manipulation experiment was conducted to test the establishment of seeds and seedlings under soil disturbance and sagebrush removal. Seed has been collected for storage and propagation studies.

  • 08/26/2020
  • Orthodox Seed Banking

Maintain a seed bank that represents the genetic diversity of the species. Seed has been collected for storage and propagation studies.

  • 08/26/2020
  • Seed Collection

Maintain a seed bank that represents the genetic diversity of the species. Seed has been collected for storage and propagation studies.

Nature Serve Biotics
  • 05/02/2017

Endemic to small area in Grand County, Colorado, mostly near a single creek. Construction of a dam in 1995 flooded at least 1 occurrence and impacted others. Other threats to this species include off-road vehicles, road maintenance, oil and gas drilling, and mining.

Carol Dawson
  • 01/01/2010

Off-road vehicle use, mineral exploration, Muddy Creek Reservoir recreational development, private development stimulated by the construction of the reservoir. (Von Bargen 1997)

Carol Dawson
  • 01/01/2010

Occurs in scattered colonies over a 15 mile range with ca. 25,000-50,000 individuals. (USFWS 1989, Von Bargen 1997)

Carol Dawson
  • 01/01/2010

The populations surrounding Kremmling, CO have been monitored by Denver Botanic Gardens since 1993. Additionally, a habitat manipulation experiment was conducted to test the establishment of seeds and seedlings under soil disturbance and sagebrush removal. Seed has been collected for storage and propagation studies.

Carol Dawson
  • 01/01/2010

Since the time of listing, the Bureau of Land Management has initiated habitat purchases, land exchanges, and formal land management designations (including Areas of Critical Environmental Concern) for this species. (USGS 2002)

Carol Dawson
  • 01/01/2010

Continue research to determine best habitat management practices for this species. Negotiate with habitat owners and managers to put best management practices in place. Continue monitoring to get more data on reproductive success and population trends.

Carol Dawson
  • 01/01/2010

Maintain a seed bank that represents the genetic diversity of the species.

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Photos
Nomenclature
Taxon Astragalus osterhoutii
Authority M.E. Jones
Family Fabaceae
CPC Number 461
ITIS 25618
USDA ASOS
Common Names Osterhout milkvetch | Kremmling milkvetch | Osterhout's milk-vetch | Osterhout milk-vetch | Kremmling milkvetch
Associated Scientific Names Astragalus osterhoutii | Lonchophaca osterhoutii
Distribution Colorado endemic (Muddy and Troublesome Creek drainages, Grand Co.). (Spackman 1997)
State Rank
State State Rank
Colorado S1
Habitat

Highly seleniferous, grayish-brown clay soils derived from shales of the Niobrara, Pierre and Troublesome formations (USFWS 1998, 1989, 1992). On moderate slopes, sometimes growing up through sagebrush at elevations of 7400-7900 feet. The milkvetch is found in badlands of shale and siltstone barrens in high elevation sagebrush habitat. (Spackman 1997).

Ecological Relationships

Ecological relationships are unknown.

Pollinators
Common Name Name in Text Association Type Source InteractionID
Bees
Polylectic bees Confirmed Pollinator Link
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

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