''Asclepias welshii'' is a rare species of

milkweed ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans ...

known by the common name Welsh's milkweed. It is native to southern

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

and northern

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, where there are four known occurrences remaining.The Nature Conservancy
/ref> Most of the plants occur in Coral Pink Sand Dunes State Park, where the habitat has been degraded in many areas by off-road vehicle use.USFWS
Final rule determining ''Asclepias welshii'' (Welsh’s Milkweed) to be a threatened species with critical habitat.
''Federal Register'' October 28, 1987. It is a federally listed

threatened species Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensa ...

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.Holmgren, N. H. and P. K. Holmgren. (1979). A new species of ''Asclepias'' (Asclepiadaceae) from Utah. ''Brittonia'' 31:1 110-14. It grows from a sturdy

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

system that anchors it in the unstable sands of its native

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

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

bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

at the base, and all the plants in one colony may actually be one individual with clones.Palmer, B. C. and L. Armstrong
Demography and monitoring of Welsh's milkweed (''Asclepias welshii'') at Coral Pink Sand Dunes.
/ref> 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.Center for Plant Conservation
A pioneer species of blowouts, it often grows alongside

blowout grass ''Redfieldia'', known as blowout grass, is a monotypic genus in the grass family (Poaceae). The sole species, ''Redfieldia flexuosa'', is native to sandhills in the western and central United States. The plants grow in small clusters, protecting ...

(''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

inflorescence An 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. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

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 follicle containing large hair-tufted seeds that measure at least 2 centimeters in length. Many plants do not produce many mature fruits and undergo

vegetative reproduction Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant or spec ...

, 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 Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands. Headquartered in Washington DC, and with oversight over , it governs one eighth of the country's la ...

, 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 Wilderness The Paria Canyon-Vermilion Cliffs Wilderness is a wilderness area located in northern Arizona and southern Utah, United States, within the arid Colorado Plateau region. The wilderness is composed of broad plateaus, tall escarpments, and deep can ...

, where there is a widespread occurrence.Hughes, L. E. (2000)
Monitoring update on four listed plants on the Arizona Strip.
In: Maschinski, J. and L. Holter, Eds. ''Southwestern rare and endangered plants: proceedings of the third conference.'' USDA FS. The plant also occurs south of the Utah border in Arizona. This population is on

Navajo Nation The Navajo Nation ( nv, Naabeehó Bináhásdzo), also known as Navajoland, is a Native American reservation in the United States. It occupies portions of northeastern Arizona, northwestern New Mexico, and southeastern Utah; at roughly , the ...

territory, which is remote, unmonitored, and not thought to be impacted by human activity.

References

External links

{{Taxonbar, from=Q4803920 welshii Endemic flora of the United States Flora of Arizona Flora of Utah Flora of the Colorado Plateau and Canyonlands region Plants described in 1979 Critically endangered flora of the United States