CPC Plant Profile: Mancos Milkvetch
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Plant Profile

Mancos Milkvetch (Astragalus humillimus)

The flowers of this species are lavender, about 1 centimeter long, and have a sweet, pungent smell. Photo Credit: Joyce Maschinski
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Fabaceae
  • State: CO, NM, NN
  • Nature Serve ID: 147602
  • Date Inducted in National Collection: 03/05/1993

Mancos milkvetch is a diminutive, tufted perennial that is found in rock crevices. The leaves have spines along their central veins that remain after the leaflets fall. The plant flowers in late April and early May producing pale lavender to purple blooms. (ESIS 2002) Reaching for a closer look at the pale lavender to purple flowers can be a prickly experience. Astragalus humillimus was rediscovered near Farmington, New Mexico, in 1980. It was formerly known from only a single collection made in 1875. It is currently known from 13 sites, 10 in New Mexico, and 3 in Colorado. High mortality occurs during periods of extended drought, but the populations regenerate from seed during more favorable years. (New Mexico Rare Plant Technical Council 1999)

Participating Institutions
Updates
  • 08/27/2020
  • Propagation Research

Seed germination trials have been completed. In cultivation, the plants are particularly sensitive to over and under watering. Maintaining in cultivation has been difficult

Nature Serve Biotics
  • 05/02/2017

A narrow endemic of the Four Corners region. All the populations are in an area being intensively developed for energy resources. Declines from 1989 to 2008 have been observed. Threats have increased.

Joyce Maschinski, Ph.D.
  • 01/01/2010

Threats include: limited distribution mining utility corridor maintenance (USFWS 1985)

Joyce Maschinski, Ph.D.
  • 01/01/2010

Only four populations were known at the time of listing, totaling around 7,000 individuals. All known populations were located in New Mexico on Bureau of Land Management and Navajo Indian Reservation lands. (USFWS 1985) Since the time of listing, additional populations have been found both in New Mexico and Colorado. There are now nine populations known to exist at thirteen sites that vary in size from 200 to 7700 plants. All the populations are in an area being intensively developed for energy resources. (NatureServe Explorer 2002)

Joyce Maschinski, Ph.D.
  • 01/01/2010

None known.

Joyce Maschinski, Ph.D.
  • 01/01/2010

None known.

Joyce Maschinski, Ph.D.
  • 01/01/2010

The plants occur in an area of active oil and gas development. Populations are small and could be eliminated by energy development, road building, and other surface disturbance.

Joyce Maschinski, Ph.D.
  • 01/01/2010

Seed germination trials have been completed. In cultivation, the plants are particularly sensitive to over and under watering. Maintaining in cultivation has been difficult

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Photos
Nomenclature
Taxon Astragalus humillimus
Authority Gray
Family Fabaceae
CPC Number 414
ITIS 25539
USDA ASHU
Common Names Mancos milkvetch | Mancos milk-vetch
Associated Scientific Names Astragalus humillimus | Phaca humillima | Tragacantha humillima
Distribution New Mexico, San Juan County; Colorado, Montezuma County; from Mancos Canyon, Colorado, southward to just south of the San Juan River in San Juan County, New Mexico. (New Mexico Rare Plant Technical C
State Rank
State State Rank
Colorado S1
New Mexico S1
Navajo Nation 2
Habitat

Cracks or eroded depressions on sandstone rimrock ledges and mesa tops in Point Lookout sandstone, which is a Cretaceous sandstone that is part of the larger Mesa Verde stratigraphic series; 1,500-1,800 m (5,000-6,000 ft.) in elevation. (New Mexico Rare Plant Technical Council 1999)Associated plants include Oryzopsis hymenoides, Gutierrezia sarothrae, Yucca angustissima, and Artemisia tridendata. (USFWS 1985)

Ecological Relationships

When in flower, this plant is often covered with butterflies, including Vanessa carduri (painted lady butterfly), which has been identified as a pollinator of this species (USFWS 1985).

Pollinators
Common Name Name in Text Association Type Source InteractionID
Bees
Honey bees Honey bee Floral Visitor Link
Leaf-cutting bees Osmia scullini Confirmed Pollinator Link
Leaf-cutting bees Osmia titusi Confirmed Pollinator Link
Butterflies & Moths
Butterflies Floral Visitor Link
Brush-footed butterflies Vanessa cardui Floral Visitor Link

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