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A Comprehensive Guide to Welsh’s Milkweed (Asclepias welshii)

Welsh’s Milkweed (Asclepias welshii) is a herbaceous perennial that is native to the states of Arizona and Utah in the United States. This plant is a host to the Queen (Danaus gilippus) and Monarch (Danaus plexippus) butterflies. Growing from 1 to 3.5 feet tall, this species grows in sand dunes. The cream flowers bloom from June to August and the plant is hardy in zones 8-10.

Taxonomy and Naming of Welsh’s Milkweed (Asclepias welshii)

Herbarium specimen of welsh's milkweed (Asclepias welshii).
Herbarium Specimen — Asclepias welshii N.H.Holmgren & P.K.Holmgren collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)

Taxonomy

Welsh’s Milkweed (Asclepias welshii) was originally named and described by Noel H. Holmgren and Patricia K. Holmgren in 1979. It has kept this name since and is a member of the Dogbane Family (Apocynaceae).

Meaning of the Scientific and Common Names

Scientific Name

The genus name, Asclepias, is named for the Greek god of healing, Asklepios (Flora of Wisconsin). The species name, welshii, is a Latinized version of “welsh”, who the plant is named.

Common Name and Alternative Names

The common name is in honor of Stanley Welch, who wrote the Flora of Utah (Holmgren and Holmgren 1979).

Physical Description

Close-up of flower cluster of welsh's milkweed (Asclepias welshii).
Flowers of Welsh’s Milkweed — Asclepias welshii N.H.Holmgren & P.K.Holmgren observed in United States of America by Matt Berger (licensed under CC BY 4.0)
  • Plant Type: This plant is a herbaceous perennial.
  • Height: 1 to 3.5 feet tall
  • Stem: The stems are simple and erect (Heil 2013). This plant has a rhizome that helps support it in the sand (Wikipedia).
  • Leaves: The leaves are opposite, sessile to subsessile, entire, elliptic to ovate or oval, and are 2.5 to 6 inches long and 1 to 3 inches wide. The leaves are coriaceous and white-woolly (Heil 2013).
  • Flower color: cream with a rose tint (Heil 2013) or pale green (Welsh, et al 1987).
  • Blooming period: This plant blooms from June to August.
  • Fruiting type and period: This plant has follicles that mature in the late summer and fall.

Range of Welsh’s Milkweed in the United States and Canada

Range map of welsh's milkweed (Asclepias welshii) in the United States and Canada.
Range Map Credit: Kartesz, J.T., The Biota of North America Program (BONAP). 2023.(website https://bonap.org/). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2023. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]

This milkweed species is native to the states of Arizona and Utah in the United States.

Habitat

Coral pink sand dunes in kane county, utah.
Coral Pink Sand Dunes — LBM1948, CC BY-SA 4.0, via Wikimedia Commons

This species grows on the coral pink sand dunes (Welsh and Chatterly 1985).

Hosted Insects

Monarch butterfly (Danaus plexippus) on goldenrod.
Monarch Butterfly on Goldenrod — ALAN SCHMIERER from southeast AZ, USA, CC0, via Wikimedia Commons

Other Supported Wildlife

Bumblebee on pink flower.
Bumblebee on Flower — Weerlicht, CC0, via Wikimedia Commons

This species is a nectar source to other butterflies, skippers, bees, and wasps during the growing season. It has noted to be visited by the central bumblebee (Bombus centralis), Ruidoso Sweat Bee (Halictus insulsus), and an osmine bee (Heriades timberlakei) (Wilson 2021).

Frequently Asked Questions

Is this plant poisonous?

Like other milkweeds, it has cardiac glycosides (cardenolides) and is considered to be poisonous with ingestion. However, it has been noted as not being toxic to livestock (NRCS Plant Guide to Welsh’s Milkweed (PDF)).

Does this plant have any ethnobotanical uses?

The Native American Ethobotanical Database does not cite this species specifically, but milkweeds in general have been used for pharmaceuticals, fibers, and foods.

How is this plant distinguished from other milkweeds?

This milkweed is similar to the broad-leaf milkweed (Asclepias latifolia), but broad-leaf milkweed has oribicular leaves with a notched apex and , whereas this species has elliptic leaves and no notch. In addition, this species has narrow unbels (3-4 cm) versus the wider umbels (5-8 cm) of A. latifolia (Sundell 1994). This species is separated from the Rosae species of Asclepias by having anther wings that are broadest in the middle (Holmgren and Holmgren 1979).

Is this plant invasive?

This plant has not been noted as being weedy.

Gardening with Welsh’s Milkweed

Plants of welsh's milkweed (Asclepias welshii) in sand dunes.
Plants of Welsh’s Milkweed — Asclepias welshii N.H.Holmgren & P.K.Holmgren observed in United States of America by Matt Berger (licensed under CC BY 4.0)

Hardiness

This species is hardy in zones 8-10. If your garden is within these zones and you have the right growing conditions (soil, moisture and exposure), you may well be able to grow this plant. However, if planted outside of its range, the hosted species may not recognize the plant or be harmed by ingesting a different species with an unfamiliar chemical composition.

Optimal Conditions

This species can grow in full sun to partial-shade in moist well-drained soil.

References

  • Heil, Kenneth D., Steve L. O’Kane, Linda Mary Reeves, Arnold Clifford. 2013. Flora of the Four Corners Region: Vascular Plants of the San Juan River Drainage. (St. Louis: Missouri Botanical Garden).
  • Holmgren, Noel H. and Patricia K. Holmgren. 1979. A New Species of Asclepias (Asclepiadaceae) from Utah. Brittonia 31: 110-114.
  • Sundell, Eric. 1994. Asclepiadaceae Milkweed Family. Journal of the Arizona-Nevada Academy of Science 27(2): 169-187.
  • Welsh, Stanley L., N. Daune Atwood, Sharel Goodrich, and Larry Higgins. 1987. A Utah Flora. Great Basin Naturalist 9: 1-895.
  • Welsh, Stanley L. and Matthew L. Chatterley. 1985. Utah’s Rare Plants Revisted. Great Basin Naturalist 45(2): 173-236.
  • Wilson, Joseph S. 2021. What North American bees are associated with milkweed (Asclepias) flowers? Western North American Naturalist 81(2): 171-180.
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Robert Coxe

Robert Coxe

Robert Coxe is a professional ecologist and botanist who has worked as the State Ecologist of Delaware and as an ecologist for the Western Pennsylvania Conservancy. He is also a former Past-President of the Pennsylvania Academy of Science. He currently is an innkeeper at McMullen House Bed & Breakfast LLC and a web designer and owner for Silphium Design LLC.

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