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A Comprehensive Guide to Desert Milkweed (Asclepias erosa)

Desert Milkweed (Asclepias erosa) is a herbaceous perennial that is native to the southwestern United States. This plant is a host to the Queen (Danaus gilippus) and Monarch (Danaus plexippus) butterflies. Growing from 1 to 4 feet tall, this species has white, cream to yellow flowers that bloom from April to October. It is hardy in zones 4-10.

Taxonomy and Naming of Desert Milkweed (Asclepias erosa)

Herbarium specimen of desert milkweed (Asclepias erosa).
Herbarium Specimen — Asclepias erosa Torr. collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)
Type specimen of desert milkweed (Asclepias erosa).
Type Specimen of Desert Milkweed — Asclepias erosa Torr. collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)

Taxonomy

Desert Milkweed (Asclepias erosa) was named and described by John Torrey, an American botanist, in 1859. The species 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, erosa, comes from the erose margins of the leaves.

Common Name and Alternative Names

The common name of the plant comes from its preferred habitat. Other common names include California desert milkweed and giant sand-milkweed.

Physical Description

Close-up of white flowers of desert milkweed (Asclepias erosa).
Desert Milkweed (Asclepias erosa) — Joshua Tree National Park, Public domain, via Wikimedia Commons
  • Plant Type: This plant is a herbaceous perennial. This is one of the largest milkweeds in the US (Woodson 1954).
  • Height: 1 to 4 feet
  • Stem: The stem is pubescent when young, but becomes more glabrous with age. The base can be woody (Woodson 1954) and branched.
  • Leaves: The leaves are opposite, sessile to short-petiolate, simple, erose (wrinkled), and lanceolate in shape. The leaves are 1.5 to 10 inches long and 1 to 4.5 inches wide.
  • Flower color: white, cream, green to yellow with greenish-white to yellow-brown hoods
  • Blooming period: This plant blooms from April to October.
  • Fruiting type and period: This plant has follicles that mature in the late summer and fall.

Range of Desert Milkweed in the United States and Canada

Range map of desert milkweed (Asclepias erosa) 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 southwestern United States and is not considered rare in any part of its range. It is also native to northern Mexico around the Baja Peninsula.

Habitat

Mojave desert in California.
Mojave Desert — Thomas Farley, CC0, via Wikimedia Commons

This species grows in washes, roadsides, and sandy plains.

Hosted Insects

Monarch butterfly on green flower.
Green Flower with Monarch Butterfly (Danaus plexippus) — U.S. Fish and Wildlife Service, Public domain, via Wikimedia Commons

This species is a host for the Monarch Butterfly (Danaus plexippus), the Queen Butterfly (Danaus gilippus), and possibly the White-lined Sphinx (Hylas lineata).

Other Supported Wildlife

Bumblebee on pink flower.
Pink flower with Bumblebee — Joaquim Alves Gaspar, Public domain, via Wikimedia Commons

This species is a nectar source to other butterflies, skippers, bees, and wasps during the growing season.

Frequently Asked Questions

Is this plant poisonous?

Like other milkweeds, it has cardiac glycosides (cardenolides) and is considered to be poisonous with ingestion.

Does this plant have any ethnobotanical uses?

The Native American Ethobotanical Database shows that this plant has been used for candy making.

How is this plant distinguished from other milkweeds?

This species is similar to the indian milkweed (Asclepias eriocarpa) and the mojave milkweed (Asclepias nyctaginifolia), but the wavy leaves of desert milkweed separate it from the other species.

Is this plant invasive?

This plant has not been shown to be invasive and has a fairly restrictive habitat.

Gardening with Desert Milkweed

Add Desert Milkweed to Your Garden

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Plant with greenish-yellow flowers of desert milkweed (Asclepias erosa).
Flowers of Desert Milkweed (Asclepias erosa) — Joshua Tree National Park, Public domain, via Wikimedia Commons

Hardiness

This species is hardy in zones 4-10. 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 grows best in places it can receive full to partial sun and has dry sandy soils.

Planting This Milkweed

The seeds of this species, require a period of cold stratification in order to germinate. Because of this it is best to plant the seeds in the fall or early winter. If you get your seeds commercially, make sure that they have been cold stratified.

References

  • Woodson, Robert E. 1954. The North American Species of Asclepias L. Annals of the Missouri Botanical Garden 41: 1-211.
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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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