CPC Plant Profile: Cushenbury Milkvetch
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Plant Profile

Cushenbury Milkvetch (Astragalus albens)

This small, silvery-white herb is a member of the pea family, a fact that is readily apparent when looking at its seed pods, as shown here. Photo Credit: Valerie Soza
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Fabaceae
  • State: CA
  • Nature Serve ID: 159120
  • Date Inducted in National Collection: 02/09/1992

Astragalus albens is a small, silvery-white, low-growing perennial herb of the pea family. It is a member of an increasingly rare suite of 5 endemic plant species restricted to carbonate deposits in the San Bernardino Mountains of southern California. This attractive plant blooms March-May, producing 5-14 purple flowers at the tips of the stems, which grow to about 1 foot (30 dm) in diameter. Cushenbury milkvetch is a federally-listed endangered species, with nearly all of its sites located on land that is actively mined or maintained for future mining (USFWS 1997).

Participating Institutions
Updates
Center for Plant Conservation
  • 08/17/2021
  • Orthodox Seed Banking

In 2021, CPC contracted the California Botanic Garden to recollect seed from a population currently held in long term orthodox seed storage as part of an IMLS-funded seed longevity experiment. The National Laboratory for Genetic Resources Preservation will evaluate how germination tested viability and RNA Integrity of seed lots decline over time in storage.

  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 5 accessions of Astragalus albens in orthodox seed collection. There are as many as 5253 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, California Botanic Garden has collected 2 seed accessions of Astragalus albens from 2 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 25 maternal plants

Nature Serve Biotics
  • 05/02/2017

Restricted to a carbonate belt in the northeastern San Bernardino Mountains, San Bernardino County, California. Approximately 16 occurrences are believed extant (with another 2 historical and 1 of unknown status) within an area of approximately 80 square kilometers. Population size was estimated to be 7000-7500 plants, but is likely less in drought years. Habitat destruction and degradation associated with limestone mining is the major threat to this species. Other threats include off-highway vehicle use, target shooting, road building and maintenance, trash dumping, and potential development. The U.S. Fish and Wildlife Service (2002) has designated Critical Habitat and the U.S. Forest Service has developed the Carbonate Habitat Management Strategy (2003) with the aim of mitigating these threats.

Valerie Soza
  • 01/01/2010

Threats and disturbances to the natural habitat of carbonate endemic plants within this region are primarily associated with limestone mining and include destruction of habitat by open or terraced mining techniques and quarries and associated overburden d

Valerie Soza
  • 01/01/2010

Cushenbury milkvetch is known from 30-50 small occurrences with a total estimate of 2,000-7,000 individuals. Sizes of populations fluctuate with rainfall patterns, with larger-sized populations in years of substantial rain (USFWS 1997; Soza pers. comm.).

Valerie Soza
  • 01/01/2010

Research has been conducted on habitat characteristics of this particular species in the San Bernardino Mountains with respect to restoration potential (Gonella and Neel 1993).

Valerie Soza
  • 01/01/2010

The majority of carbonate deposits within the San Bernardino Mountains are owned by the USDA Forest Service, San Bernardino National Forest (SBNF), which has developed a forest management plan that aims to conserve some of the existing populations of the carbonate endemics by setting aside refugia. As part of this plan, the SBNF has supported ongoing surveys of carbonate habitat within the SBNF to expand knowledge of species distribution patterns and assist in identification of refugia potential (USFWS 1997).

Valerie Soza
  • 01/01/2010

Management needs that have been identified by the USFWS include protection of significant extant populations by developing a reserve system on federally owned land of occupied areas, buffer zones, and habitat connections; restoring habitat, reintroduction efforts and enhancing populations; monitoring populations; and conducting surveys and taxonomic assessments to locate new populations and resolve questions about the identity of several existing populations (USFWS 1997).

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Photos
Nomenclature
Taxon Astragalus albens
Authority Greene
Family Fabaceae
CPC Number 7000
ITIS 25406
USDA ASAL4
Common Names Cushenbury milkvetch | Cushenbury oxytheca | silvery white milkvetch | Cushenbury milk-vetch
Associated Scientific Names Astragalus albens | Hamosa albens
Distribution It is distributed over a 15 mile (24 km) stretch on the north side of the San Bernardino Mountains (Transverse Ranges), San Bernardino County, California, from Furnace Canyon southeast to Arrastre Cre
State Rank
State State Rank
California S1
Habitat

This species is found on cobbly/gravelly soils derived from decomposing limestone bedrock on gentle slopes and in rocky washes that have received limestone outwash. It grows in habitats with open canopies, low competition, and little organic material. Primary associated communities are pinyon-juniper woodlands with blackbush or flannelbush, and blackbrush scrub between 5,000 and 6,600 feet (1,500-2,000 m) elevation (USFWS 1994, 1997).

Ecological Relationships

Little is known on the pollination ecology, seed dispersal mechanisms, and seedbank dynamics of this species (USFWS 1997).

Pollinators
Common Name Name in Text Association Type Source InteractionID

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