Asclepias welshii is a rare species of
milkweedAsclepias L. , the milkweeds, is a genus of herbaceous perennial, dicotyledonous plants that contains over 140 known species...
known by the common name
Welsh's milkweed. It is native to southern
UtahUtah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
and northern
ArizonaArizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, where there are four known occurrences remaining. Most of the plants occur in
Coral Pink Sand Dunes State ParkCoral Pink Sand Dunes State Park is a state park of Utah, USA, located between Mount Carmel Junction and Kanab, south and west of U.S. Highway 89 in southwestern Utah...
, where the habitat has been degraded in many areas by
off-road vehicleAn off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
use. It is a federally listed
threatened speciesAn 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...
of the United States.
This is an erect perennial herb growing up to a meter tall. It is "a rather handsome milkweed" which "is a very distinctive species with no obvious close relatives," according to Holmgren and Holmgren, who described the plant in 1979. It grows from a sturdy
rhizomeIn botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
system that anchors it in the unstable sands of its native
duneIn physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
habitat, with several aboveground stems arising from one rhizome system. For this reason, it is not possible to get an accurate count of how many individual plants actually exist, since several widely spaced stems may actually belong to one plant; estimates of the number of plants remaining are based on stem counts. The rhizomes can penetrate very deeply into the dunes, possibly even to the
bedrockIn stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
at the base, and all the plants in one colony may actually be one individual with
clonesCloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
. There are perhaps 20,000 stems, according to count data, for an unknown number of genetically separate individuals. The plant colonizes empty dunes and is eventually outcompeted when other plant species move into the area. A pioneer species of
blowoutsBlowouts are sandy depressions in a sand dune ecosystem caused by the removal of sediments by wind.Blowouts occur in partially vegetated dunefields or sandhills. A blowout forms when a patch of protective vegetation is lost, allowing strong winds to "blow out" sand and form a depression...
, it often grows alongside
blowout grassBlowout grass, Redfieldia flexuosa, is a grass that can be found on sand dunes. The plants grow in small clusters, protecting each other from the harsh desert conditions.-Range:...
(
Redfieldia flexuosa), a resident of this habitat type.
The upright stem has several oppositely arranged pairs of leaves up to 9 centimeters long by 6 wide. The stem and leaves are covered in a dense coat of woolly hairs, especially the new leaves. The hairs may prevent the plant from losing water in its dry habitat, or protect the plant tissues from the scouring action of windblown sand. The
inflorescenceAn inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
is a dense ball of many flowers, the whole head measuring around 7 centimeters wide. Each flower is just under a centimeter long and white in color with a pale pink center. The fruit is a warty
follicleIn botany, a follicle is a dry unilocular many-seeded fruit formed from one carpel and dehiscing by the ventral suture in order to release seeds, such as in larkspur, magnolia, banksia, peony and milkweed....
containing large hair-tufted seeds that measure at least 2 centimeters in length. Many plants do not produce many mature fruits and undergo
vegetative reproductionVegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...
, spreading via the rhizome. The plant may be difficult to identify if not in its mature form; the two immature forms look very different. The smallest form which emerges through the sand from the rhizome has narrow linear leaves very unlike those the mature plant, and the secondary form has leaves intermediate to the two.
The largest population of the plant at Coral Pink Dunes State Park, particularly the half managed by the
Bureau of Land ManagementThe 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...
, has been impacted by off-road vehicle use, but such activity in the area has not increased since the plant was listed for protection. Park staff keeps track of off-road vehicle activity on the grounds. ORVs are not allowed in the
Paria Canyon-Vermilion Cliffs WildernessThe Paria Canyon-Vermilion Cliffs Wilderness is a wilderness area located in northern Arizona and southern Utah, USA, within the arid Colorado Plateau region. The wilderness is composed of broad plateaus, tall escarpments, and deep canyons....
, where there is a widespread occurrence. The plant also occurs south of the Utah border in Arizona. This population is on
Navajo NationThe 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...
territory, which is remote, unmonitored, and not thought to be impacted by human activity.