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Plant Profile

Humboldt Milkvetch (Astragalus agnicidus)

Astragalus agnicidus has clusters of small white flowers and pinnately compound leaves. Photo Credit: Andrea Pickart

Global Rank: G2 - Imperiled
Legal Status: N/A
Family: Fabaceae
State: CA
Nature Serve ID: 132940
Lifeform: Forb/herb
Date Inducted in National Collection: 04/04/1991

Description:

Throughout history, humans have systematically eradicated plants and animals that seem to pose a threat to their livestock or crops. Bears, wolves, coyotes, and even condors have all been victims of ranchers' guns and traps. Astragalus agnicidus has fallen victim to the rancher's shovel and herbicide use. Fortunately, recent changes in scientific thought and public opinion have helped people to see these species not as "threats" but as integral parts of native ecosystems, and therefore, worthy of our protection. For over seventy years, the only known site containing Astragalus agnicidus was a privately owned 8-acre ranch in Humboldt County, CA. In the 1930s and 40s, the owners logged and cleared portions of their land in order to raise sheep. When several sheep were found dead, the concerned owners enlisted the help of a local County Agriculture Extension employee. He identified the "culprit" and encouraged them to eradicate the plant (although many members of the genus Astragalus are toxic to livestock, some now believe that in this instance, the real killer may have been a lupine). But the damage was done, both literally and figuratively. When the species was formally named in 1957 it was given the specific epithet of agnicidus, which means lamb killer (the lamb killing locoweed is a much less appealing common name than Humboldt milkvetch). The landowners appeared to have been successful in their quest to eradicate this plant, as in 1954, only one plant was found. No more were found and it was presumed extinct until it was re-discovered. In 1985, bulldozers were used to clear a fallen tree that was considered a fire hazard. Two years later, 25 Astragalus agnicidus plants were found in the area and another 75 were found in a nearby clearing. The canopy opening created by the fallen tree coupled with the soil disturbance caused by the heavy equipment that removed the tree created suitable conditions for the seeds, which had lain dormant in the soil for at least 30 years, to germinate (see the research and ecology sections for more). Like many others who now see the value in conserving all aspects of native ecosystems, the same family that once worked to eradicate the plant is now enthusiastic about conserving it. The population is currently protected by a voluntary agreement between the landowner and The Nature Conservancy and the land is being managed for the species' continued survival. Astragalus agnicidus was removed from the Federal Endangered and Threatened Candidate list in 1996 (U.S. Fish and Wildlife Service, 1996) largely because of this protection agreement. In 1999 and 2000, two new sites containing A. agnicidus were discovered on timberland that had recently been logged. It appears that apparently extinct species can arise, phoenix-like, out of the ashes of oblivion from naturally occurring as well as artificial seed banks.

Where is Humboldt Milkvetch (Astragalus agnicidus) located in the wild?

Habitat:

An early successional species, Astragalus agnicidus prefers disturbed sites such as logged ridges, open canopy wooded areas and scarified ground.

Distribution:

CA: Outer North Coast Range

States & Provinces:

Humboldt Milkvetch can be found in California

Which CPC Partners conserve Humboldt Milkvetch (Astragalus agnicidus)?

Rae Selling Berry Seed Bank & Plant Conservation Program

Not Sponsored

Conservation Actions

Assigned 06/09/17

California Botanic Garden

Not Sponsored

Conservation Actions

Assigned 06/09/17

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

09/01/2020

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 2 accessions of Astragalus agnicidus in orthodox seed collection. There are as many as 654 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

09/01/2020

Based on an September 2020 extract of the California Plant Rescue Database, Rae Selling Berry Seed Bank & Plant Conservation Program holds 17 accessions of Astragalus agnicidus in orthodox seed collection. There are as many as 6900 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

08/19/2020

Genetic analysis of one population of A. agnicidus utilizing isozymes (enzymes) and the role of mating system in maintaining genetic variability were examined by Bencie (1997). Astragalus agnicidus plants analyzed showed low genetic variability. Flowers were experimentally open-pollinated or self-pollinated, and five fitness variables were measured: seed set, seed weight, germination, survival, and seedling weight. Fitness was reduced to some extent in the selfed progeny for all variables, but the difference was only significant in regards to seedling survival.

08/19/2020

Germination requirement study. 30 minutes scarification in sulfuric acid followed by 20 days of stratification at 4C lead to an 88.5% germination rate. Less than 5% of seeds germinated if scarification was not performed (Hiss 1990). Light requirement study. High light treatments showed greater seedling emergence, earlier leaf emergence, and produced more robust plants compared to low or moderate light treatments (Enberg 1990). Estimation of reproductive output (number of pods and number of seeds per pod) for one year (Pickart and Stauffer 1994). Genetic analysis of one population of A. agnicidus utilizing isozymes (enzymes) and the role of mating system in maintaining genetic variability were examined by Bencie (1997). Astragalus agnicidus plants analyzed showed low genetic variability. Flowers were experimentally open-pollinated or self-pollinated, and five fitness variables were measured: seed set, seed weight, germination, survival, and seedling weight. Fitness was reduced to some extent in the selfed progeny for all variables, but the difference was only significant in regards to seedling survival.

08/19/2020

08/05/2020

Based on an August 2020 extract of the California Plant Rescue Database, Rae Selling Berry Seed Bank & Plant Conservation Program has collected 17 seed accessions of Astragalus agnicidus from 5 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 158 maternal plants

Nature Serve Biotics

05/02/2017

Previously not seen since 1954, Astragalus agnicidus was rediscovered in 1987. As of 2005, it is known only from two counties in California and about 50 occurrences. Many new populations have been found, but few are ranked ""good"" or better. Many plants are reported, though numbers are somewhat in question and their long-term viability is unknown. Astragalus agnicidus occurs in forested areas where the canopy has recently been opened. It is threatened by logging treatments such as herbicide application.

Edward Guerrant, Ph.D.

01/01/2010

Ecological succession (Pickart et al. 1991). Plant destruction because of toxic properties (Pickart et al. 1991). Extensive logging may actually harm populations (Bencie 2001). This may cause the stored soil seed bank to germinate all at once. Any

Edward Guerrant, Ph.D.

01/01/2010

3 sites. Two in Humboldt Co, one in Mendocino Co. One population was discovered in 1987, one in 1999, one in 2000. The population discovered in 1999 contained over 5000 individuals (CA Natural Diversity Database). While populations may be large, they are transient and their survival is dependent on suitable habitat conditions.

Edward Guerrant, Ph.D.

01/01/2010

Edward Guerrant, Ph.D.

01/01/2010

Listed as Endangered by the State of California. There is no federal status. Voluntary protection agreement between owner of the site discovered in 1987 and The Nature Conservancy of California (Landowner Contact and Registry). Fencing of largest concentrations of plants to exclude herbivores (Pickart, Hiss, and Enberg 1991) Recent surveys revealed two new populations on private land managed for timber production (Bencie 2001). Monitoring and mitigation of a large population discovered in 2000 (Bencie 2001).

Edward Guerrant, Ph.D.

01/01/2010

Study population biology (Pickart et al. 1991). Management in concert with logging to create periodic openings in the canopy and to scarify the ground (Berg and Bittman 1988). Openings created when trees are selectively removed could be managed for A. agnicidus, and then be allowed to revert to forest while other openings are created in nearby areas (Pickart, Hiss, and Enberg 1991). Populations should be large enough to promote high outcrossing rates. If populations are too small, there is a high risk of allele fixation through drift (Bencie 1997). Study chemical properties (it may be more protected if it is found to have pharmacological value) (Berg and Bittman 1988). Other members of the genus Astragalus have been found to stimulate macrophages and aid in general immunity (Moore 1993). Protect pollinators and their habitat (Bencie 1997).

Edward Guerrant, Ph.D.

01/01/2010

Collect and store seed from each of the three known populations. Collect as new plants emerge due to local disturbances. Because Astragalus agnicidus appears to have an extensive soil seed bank, it will be necessary to collect over a long period of time in order to encompass the genetic variability present in the population.