CPC Plant Profile: Welsh's Milkweed
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Plant Profile

Welsh's Milkweed (Asclepias welshii)

In the foreground is Welsh's milkweed, growing on the beautiful pink sand dunes where the species is found. Photo Credit: Joyce Maschinski
Description
  • Global Rank: N/A
  • Legal Status: N/A
  • Family: Apocynaceae
  • State: AZ, NN, UT
  • Nature Serve ID: 146639
  • Date Inducted in National Collection: 04/04/1991

Welsh's milkweed is an herbaceous perennial with extremely hairy and broad ovate leaves. Cream-colored flowers with rose-tinged centers are produced in a ball shaped cluster from May to June. Large seeds with rudimentary tufts of hairs develop and are dispersed from July to early September. However, two other growth forms are known to exist. What is designated as the primary growth form has narrow linear leaves and looks very similar to A. subverticillata. A second form exhibits intermediate leaf traits of the primary form and the first description (referred to as the mature form) and is called the secondary form. (Palmer & Armstrong 2000) This species grows in coral pink colored sand dunes and was listed as threatened in 1987 in response to increased threats of off-road vehicle (ORV) activity (USFWS 1987).

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Updates
  • 08/19/2020
  • Propagation Research

Seed germination protocol has been determined, but cultivation for more than 2 years has been problematic. Further cultivation trials are needed.

  • 08/19/2020
  • Demographic Research

Palmer and Armstrong (2000) have monitored two populations for 12 years. The species colonizes shifting dunes and tends to be outcompeted when dunes stabilize. The authors believe that education and enforcement of regulations to protect dune habitat from off-road vehicles has effectively helped to preserve the species. At the time of listing, there were thought to be no more than 11,000 individuals of this species, with populations scattered in a fairly localized area in Utah and on the Utah-Arizona state line. (USFWS 1987) There are now three Utah populations: Coral Pink Sand Dunes (ca. 10,000 individuals), 2) Sand Hills ( ca. 500 individuals), 3) Sand Cove (ca. 600 individuals). At least two others are known to exist near Page County, Arizona and in the Paria-Vermillion Cliffs Wilderness are near the Utah/Arizona border in Kane County, Utah and Coconino County, Arizona (Palmer & Armstrong 2000).

Nature Serve Biotics
  • 05/02/2017

Known from only six population areas with a total of approximately 20,000 above-ground stems (the number of genetic individuals is unknown). The known range includes Kane County, Utah, BLM land in Coconino County, Arizona, and Navajo Nation lands in Arizona (Navajo, Apache, and Coconino counties). The two Utah occurrences face the greatest threats, with parts of the species' very fragile sand dune habitat impacted primarily by off-road vehicle activity. The two Navajo Nation occurrences are smaller, but are relatively remote and are believed to have good to excellent viability. The two occupied areas on BLM land in Arizona are relatively remote, and not affected by ORV disturbance.

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

As stated by the U.S. Fish and Wildlife Service at the time of listing (USFWS 1987), threats include: Off-road vehicles Drought

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

At the time of listing, there were thought to be no more than 11,000 individuals of this species, with populations scattered in a fairly localized area in Utah and on the Utah-Arizona state line. (USFWS 1987) There are now three Utah populations: Coral Pink Sand Dunes (ca. 10,000 individuals), 2) Sand Hills ( ca. 500 individuals), 3) Sand Cove (ca. 600 individuals). At least two others are known to exist near Page County, Arizona and in the Paria-Vermillion Cliffs Wilderness are near the Utah/Arizona border in Kane County, Utah and Coconino County, Arizona (Palmer & Armstrong 2000).

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

Palmer and Armstrong (2000) have monitored two populations for 12 years. The species colonizes shifting dunes and tends to be outcompeted when dunes stabilize. The authors believe that education and enforcement of regulations to protect dune habitat from off-road vehicles has effectively helped to preserve the species.

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

BLM has monitored the species for the past 12 years and has been enforcing ORV regulations to protect dunes. (Palmer & Armstrong 2000)

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

The possibility of creating new dune habitat adjacent to occupied habitat could be explored.

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

Seed germination protocol has been determined, but cultivation for more than 2 years has been problematic. Further cultivation trials are needed.

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Photos
Nomenclature
Taxon Asclepias welshii
Authority N. Holmgren & P. Holmgren
Family Apocynaceae
CPC Number 312
ITIS 30325
USDA ASWE3
Common Names Welsh's milkweed
Associated Scientific Names Asclepias welshii
Distribution Kane Co., UT, near Kanab, and adjacent Coconino Co., AZ, near the Utah-Arizona state line.
State Rank
State State Rank
Arizona S1
Navajo Nation 4
Utah S1
Habitat

A. welshii grows on active sand dunes in sagebrush, juniper, and ponderosa pine communities, between 4700 and 6250 ft in elevation. (NatureServe 2001)Co-occurring species include Wyethia scabra, Calamovilfa gigantea, Chrysothamnus nauseosus and Sophora stenophylla.

Ecological Relationships

This species is adapted to the naturally unstable sand dunes on which it occurs. As a sand dune-adapted species, this plant has a rhizomatous rootstock that is able to hold sand in place, which initiates the stabilization of the sand dune on which it grows. (USFWS 1987) Reproduces mainly by rhizomes, but by seed when conditions are right (Palmer & Armstrong 2000). While a number of species in the Asclepias genus contain toxins that make them poisonous to grazers (including cattle), this species has been shown to be palatable and non-toxic to range livestock. However, cattle seldom traverse the sand dunes where this species occurs, so grazing is likely not a major threat to this species. (USFWS 1987)

Pollinators
Common Name Name in Text Association Type Source InteractionID
Bees
Leaf-cutting bees Anthidium rodecki Floral Visitor Link
Honey bees Apis mellifera Confirmed Pollinator Link
Bumble bees Bombus bifarius Confirmed Pollinator Link
Centris bees Ceratina nanula Floral Visitor Link
Sweat bees Dialictus albohirtus Floral Visitor Link
Sweat bees Dialictus ruidosensis Floral Visitor Link
Leaf-cutting bees Heriades timberlakei Floral Visitor Link
Carpenter bees Xylocopa californica arizonensis Confirmed Pollinator Link
Butterflies & Moths
Brush-footed butterflies Euphydryas anicia hermosa Confirmed Pollinator Link
Noctuid moths Euxoa aurulenta Confirmed Pollinator Link
Other
Sand wasps Bembix americana Floral Visitor Link
Sand wasps Microbembex californica Floral Visitor Link
Square-headed wasps Mimesa Floral Visitor Link
Square-headed wasps Oxybelus californicus Floral Visitor Link
Paper wasps Polistes dorsalis Floral Visitor Link
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

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