CPC National Collection Plant Profile

Astragalus mulfordiae

Roger Rosentreter

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CPC National Collection Plant Profile

Astragalus mulfordiae

Common Name: 
Mulford's milkvetch
M.E. Jones
Growth Habit: 
CPC Number: 


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 Fish & WildLife

Astragalus mulfordiaeenlarge
Photographer: Roger Rosentreter
Image Owner: Boise BLM

Astragalus mulfordiae is Fully Sponsored
Primary custodian for this plant in the CPC National Collection of Endangered Plants is: 
Edward Guerrant, Ph.D. contributed to this Plant Profile.

Astragalus mulfordiae

Mulford's milk vetch is in danger of being ignored out of existence. Like many other species not particularly attractive to the general public, Astragalus mulfordiae does not get the attention that it deserves. While this plant may not qualify beautiful by the average member of the public, does not cure cancer, and is not found in a highly populated area, it does play an important role in its native ecosystem and is no less deserving of protection than a beautiful lily. There appear to be many populations, but many, especially in Idaho, occur on privately owned land, much of which is grazed. In Idaho, 18 of the 34 known populations (over half) occur entirely on private land. Only 8 populations occur entirely on Federal land. Plants in Oregon have had better luck. Until 1988, only one population was known in Oregon. As of 1995, 38 are known, 33 of which are on Bureau of Land Management property, and 5 of which are on Private land (DeBolt 1995). Why is it worrisome that so many populations in Idaho are on private land? Those populations on private land are not subject to laws or regulations that the federal or state government may make in regards to this rare species.

Distribution & Occurrence

State Range
State Range of  Astragalus mulfordiae
  Found in shrub-steppe and desert shrub communities in the semi-arid, cold-desert region of southeast Oregon and southwest Idaho. The mean annual temperature is 50-52F (10-11C) with 8-13 inches (20-33cm) of precipitation. Plants are found on moderately steep to steep southeast, south, and southwest facing slopes consisting of old river deposits, sandy areas near rivers, sandy bluffs and dune-like talus. Elevations range from approximately 2,100 to 3,200 ft (640-975 m).

  The "Western Snake River Plain," found in the Owyhee Uplands (Malheur Co.) of eastern Oregon and the Owyhee Front and Boise Foothills of western Idaho.

Number Left
  As of 1995, 34 populations in Idaho, and 38 in Oregon. (DeBolt 1995) Population sizes in Oregon vary from 1 to 1000 (ONHDB 2000).


Global Rank:  
Guide to Global Ranks
Federal Status:  
Guide to Federal Status
Recovery Plan:  

State/Area Protection
  State/Area Rank Status Date  
  Idaho S2 GP2 12/21/2001  
  Oregon S1 LE 7/12/1995  

Conservation, Ecology & Research

Ecological Relationships
  Astragalus mulfordiae occurs within the western Snake River Plain, which has a semi-arid, cold-desert climate. Here it is found in deep lacustrine and alluvial deposits of relatively coarse substrates. Astragalus mulfordiae is associated with shrub-steppe and desert shrub communities, generally among Purshia tridentata and Stipa comata (antelope bitterbrush and needle and thread grass) (DeBolt 1995).

Astragalus mulfordiae reproduces only by seed. The pollination mechanism unknown, but is most likely either flying insects or self-pollination. Seed is dispersed by gravity and wind as the stems and pods gradually weather away in the harsh winter conditions (DeBolt 1995).

The weather patterns in late winter and early spring greatly influence timing of re-growth and phenological stages. In general, re-growth begins in early March, with flowering in April, May, and sometimes in to June. Fruit maturation is in June and July followed shortly by senescence (loss of leaves) (DeBolt 1995).

Populations appear different in their abilities to withstand disturbances. Some sites have been extirpated through ORV use, cattle grazing and fire. However, there are some areas that are grazed in the spring where the plants have persisted. Some botanists have suggested that there may be a genetic difference between populations that are more susceptible or more tolerant of disturbances (DeBolt 2001).

  General habitat degradation (DeBolt 2001).
Urban expansion (DeBolt 2001).
Livestock grazing and trampling (DeBolt 1995).
Fires leading to cheatgrass (Bromus tectorum) invasion (DeBolt 1995).
Off Road Vehicle (ORV) use (DeBolt 1995).
Agricultural development (DeBolt 1995).
Scotch thistle (Onopordum acanthium) invasion (DeBolt 1995).
Herbicide drift from Scotch thistle control (DeBolt 1995).
Loss of insect pollinators from insecticide spraying to control grasshoppers (DeBolt 1995).
Road development and maintenance (DeBolt 1995).
Population isolation and fragmentation (DeBolt 2001) may lead to low genetic diversity.
Mining (DeBolt 1995).

Current Research Summary
  Monitoring studies have been conducted at several sites in Oregon, and show evidence of drastic declines in population sizes. Individuals that were grazed by cattle were weakened in the second year and absent in the third year. However, there was no control treatment, and so it cannot be concluded that livestock alone are responsible for the decline (DeBolt 1995).
Micropropagation techniques using seeds and shoot-tip explant in culture has been explored by Edson (1998).
Astragalus mulfordiae seedling establishment, adult survival and reproduction were studied at two populations between 1995 and 1997. The effects of re-vegetation (seeding) with Agropyron desertorum (or A. cristatum) and the impacts of cattle grazing on the demography of A. mulfordiae were observed. Using a visual estimate of grazing severity per plant, those plants in the seeded area that was exposed to cattle grazing were grazed more severely than the un-seeded area that had light horse grazing. Fruits per inflorescence, inflorescence per plant and adult plant survival were all significantly lower in the cattle-grazed area (David Pyke, personal communication).
Germination trials at The Berry Botanic Garden indicate no specific requirements. Seeds were scarified and then subjected to cold stratification or no cold stratification and were then placed in germination chambers with constant 68F (20C) temperatures or alternating 50F/68F (10/20C) temperatures. Several treatments resulted in 100% germination (BBG File).
Pollination studies (Idaho BLM) (DeBolt 2001).

Current Management Summary
  Most populations on BLM land in Idaho are subject to springtime grazing (DeBolt 2001)
Inventory of public lands in Idaho in the early to mid 1990's. Annual visit to many sites. Little formal monitoring (DeBolt 2001).
Monitoring of burned and seeded sites on BLM land in Oregon.
Seed from 9 sites in Oregon and 4 in Idaho collected and stored at The Berry Botanic Garden.

Research Management Needs
  Determine pollination mechanism
Study effect of grazing on population survival
Study possible genetic differences between populations north and south of the Snake River (DeBolt 2001)

Ex Situ Needs
  Collect and store seeds from across range.
Determine propagation and reintroduction protocols.


Books (Single Authors)

Barneby, R.C. 1964. Atlas of North American Astragalus. Bronx, New York: New York Botanical Garden. 1188p.

ONHP. 2001. Rare, Threatened and Endangered Plants and Animals of Oregon.

Books (Sections)

Kartesz, J.T. 1999. A synonymized checklist of the vascular flora of the U.S., Canada, and Greenland. In: Kartesz, J.T.; Meacham, C.A., editors. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden. Chapel Hill, NC.

Electronic Sources

ONHDB. (2000). Oregon Natural Heritage Program Database. Portland, Oregon.

Journal Articles

1898. (Original Publication). Contr. West. Bot. 8: 18.

Barneby, R.C. 1980. Dragma hippomanicum VI: A new Tragacanthoid Astragalus from Nevada and Idaho. Brittonia. 32, 1: 30-32.

Edson, J.L. 1998. Shoot Culture of Astragalus: Toward Conserving a Threatened Genus. Botanic Gardens Micropropagation News. 2, 3

USFWS. 1996. Notice of Reclassification of 96 Candidate Taxa. Federal Register. 61, 40: 7457-7463.

Personal Communications

DeBolt, A. 2001. E-mail communication. 12/5/01. In BBG files.

Pyke, D. 2001. Personal Communication. David Pyke. U.S. Geologic Survey, Forest & Rangeland Ecosystem Science Center, Corvallis, Oregon.


Atwood, Duane; DeBolt, Ann. 2000. Field Guide to the Special Status Plants of the Bureau of Land Management Lower Snake River District. A Bureau of Land Management Challenge Cost Share Project with Duane Atwood.

DeBolt, A. 1995. Habitat Conservation Assessment for Mulford's Milkvetch (Astragalus mulfordiae). Unpublished report. Bureau of Land Management.

Kennison, J.A. 1980. Status report for Astragalus mulfordiae. Boisie, Idaho: U.S. Fish & Wildlife Service, Boise Field Office. Unpublished report.

Moseley, R.K. 1989. Report on the Conservation Status of Astragalus mulfordiae in Idaho. Boise, ID: Idaho Department of Fish and Game. p.27 + appendices. Status Survey Report.

Rosentreter, R. 1986. Sensitive and uncommon plants in the Boise District Bureau of Land Management. Boise, ID: Bureau of Land Management, Idaho State Office. p.87.

Steele, B.; Johnson, F.; Brunsfield, S. 1981. Vascular plant species of concern in Idaho. Moscow, ID: Forest, Wildlife and Range Experiment Station. p.161.

USFWS. 1995. Habitat conservation report for Mulford's milkvetch (Astragalus mulfordiae). Boise, Idaho: U.S. Fish & Wildlife Service, Boise Field Office. Unpublished report.

  This profile was updated on 7/8/2010
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