Astragalus humillimus
Encyclopedia
Astragalus humillimus is a rare species of milkvetch
known by the common name Mancos milkvetch. It is native to a small section of the Four Corners region of the United States, where it can be found in Montezuma County, Colorado
, and San Juan County, New Mexico
. There are about nine small, localized populations on sandstone
rimrock
ledges on the mesa
s. The plant occurs in a region that is being developed for oil and gas exploration, and altered by associated activities such as road
construction and pipeline
installation. It is a federally listed endangered species
.
This is a small perennial herb forming low tufts up to 30 centimeters wide in cracks and sandy depressions in sandstone cliffs and pavement. The sandstone is of Cretaceous
origin, and local formations include the Point Lookout Sandstone
. The matted leaves are each up to 4 centimeters long and are made up of several oval or nearly rounded leaflets no more than 2 millimeters long. As the plant withers and prepares to go dormant, the leaves lose all the leaflets and persist as naked sharp spines. Blooming occurs for a short period in the spring. The plentiful tiny flowers are bright pink-purple with a spot of white streaking at the middle. The flowers are fragrant with a sweet smell and are very attractive to butterflies
. Multitudes of butterflies rest on the plant when it is in bloom. The Painted Lady
(Vanessa cardui) is a common visitor.
Some populations occur on Bureau of Land Management
land and there are a few within the bounds of the Navajo Nation
.
Astragalus
Astragalus is a large genus of about 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae, subfamily Faboideae. The genus is native to temperate regions of the Northern Hemisphere...
known by the common name Mancos milkvetch. It is native to a small section of the Four Corners region of the United States, where it can be found in Montezuma County, Colorado
Montezuma County, Colorado
Montezuma County is the southwesternmost of the 64 counties of the state of Colorado of the United States. The county population was 23,830 at U.S. Census 2000...
, and San Juan County, New Mexico
San Juan County, New Mexico
-2010:Whereas according to the 2010 U.S. Census Bureau:*51.6% White*0.6% Black*36.6% Native American*0.4% Asian*0.1% Native Hawaiian or Pacific Islander*3.5% Two or more races*7.2% Other races*19.1% Hispanic or Latino -2000:...
. There are about nine small, localized populations on sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
rimrock
Rimrock
Rimrock is the sheer rock wall at the upper edge of a plateau, canyon, or geological uplift. It may refer to either the rock formation or to the rock itself. Rimrock may be composed of almost any stone—basalt, gneiss, granite, sandstone, etc.—and is frequently layered. Many times it...
ledges on the mesa
Mesa
A mesa or table mountain is an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape....
s. The plant occurs in a region that is being developed for oil and gas exploration, and altered by associated activities such as road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...
construction and pipeline
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
installation. It is a federally listed endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
.
This is a small perennial herb forming low tufts up to 30 centimeters wide in cracks and sandy depressions in sandstone cliffs and pavement. The sandstone is of Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
origin, and local formations include the Point Lookout Sandstone
Point Lookout Sandstone
The Point Lookout Sandstone is a Cretaceous bedrock formation occurring in New Mexico and Colorado.-Description:The sandstone was first described by A. J...
. The matted leaves are each up to 4 centimeters long and are made up of several oval or nearly rounded leaflets no more than 2 millimeters long. As the plant withers and prepares to go dormant, the leaves lose all the leaflets and persist as naked sharp spines. Blooming occurs for a short period in the spring. The plentiful tiny flowers are bright pink-purple with a spot of white streaking at the middle. The flowers are fragrant with a sweet smell and are very attractive to butterflies
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
. Multitudes of butterflies rest on the plant when it is in bloom. The Painted Lady
Vanessa cardui
Vanessa cardui is a well-known colourful butterfly, known as the Painted Lady, or in North America as the Cosmopolitan. This butterfly has a strange pattern of flying in a sort of screw shape.-Distribution:...
(Vanessa cardui) is a common visitor.
Some populations occur on Bureau of Land Management
Bureau of Land Management
The Bureau of Land Management is an agency within the United States Department of the Interior which administers America's public lands, totaling approximately , or one-eighth of the landmass of the country. The BLM also manages of subsurface mineral estate underlying federal, state and private...
land and there are a few within the bounds of the Navajo Nation
Navajo Nation
The Navajo Nation is a semi-autonomous Native American-governed territory covering , occupying all of northeastern Arizona, the southeastern portion of Utah, and northwestern New Mexico...
.