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A Comprehensive Guide to Mojave Milkweed (Asclepias nyctaginifolia)

Mojave Milkweed (Asclepias nyctaginifolia) 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 0.5 to 1.75 feet tall, this species has greenish-white, pink to purple flowers that bloom from April to October. It is hardy in zones 7-9.

Taxonomy and Naming of Mojave Milkweed (Asclepias nyctaginifolia)

Herbarium specimen of mojave milkweed (Asclepias nyctaginifolia).
Herbarium Specimen — Asclepias nyctaginifolia A.Gray collected in United States of America by The New York Botanical Garden (licensed under CC By 4.0)

Taxonomy

Mojave Milkweed (Asclepias nyctaginifolia) was originally named and described by Asa Gray, an American botanist, in 1877. 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, nyctaginifolia, refers to having leaves similar to the four-o’clock family, which is the Nyctaginaceae (davesgarden.com).

Common Name and Alternative Names

The common name of the plant comes from its location. Other common names include the four-o’clock milkweed in reference to the leaves and the species name.

Physical Description of Mojave Milkweed

Plants of mojave milkweed (Asclepias nyctaginifolia) in rocks.
Plants of Mojave Milkweed — Asclepias nyctaginifolia A.Gray collected in United States of America by Utah State University (licensed under CC0 1.0)
  • Plant Type: This plant is a herbaceous perennial.
  • Height: 0.5 to 1.75 feet
  • Stem: The stem is pubescent and decumbent to ascending
  • Leaves: The leaves are opposite, simple, entire, and ovate to lanceolate in shape. The leaves are 1 to 6 inches long and 0.75 to 3 inches wide. The leaves can be thick, pubescent, and undulate (Felger, et al. 2014).
  • Flower color: greenish-white to greenish-yellow
  • 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 Mojave Milkweed in the United States and Canada

Range map of mojave milkweed (Asclepias nyctaginifolia) 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 considered to be rare in the state of California. It is also native to northern Mexico around the Baja Peninsula. Generally in other states, it is considered to be uncommon.

Habitat

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

This species grows in washes and hillsides (dry slopes (Abrams and Ferris 1951)) in the desert, roadsides and open woodlands (Arizona Cooperative Extension) grasslands (McLaughlin 2006), swales (Woodson 1954) and mesas (Verrier 2018).

Hosted Insects

Queen Butterfly on Twig.
Queen Butterfly (Danaus gilippus) — Korall, CC BY 3.0, via Wikimedia Commons

This species is a host for the Monarch Butterfly (Danaus plexippus), the Queen Butterfly (Danaus gilippus) (Grodsky, et al. 2020), the Elegant Pygarctia (Euchaetes elegans) (S. CA Acad Sci 1959) and possibly the White-lined Sphinx (Hylas lineata).

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. Mojave milkweed is also eaten by the black-tailed jackrabbit (Lepus californicus) (Grodsky, et al. 2020)

Frequently Asked Questions about Mojave Milkweed

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 as an antidiarrheal and pediatric drug.

How is this plant distinguished from other milkweeds?

This species is distinguished by the thick hoods and large flower size (Greene 1896). This species is also similar to the rush milkweed (Asclepias subulata), but the differs in that rush milkweed has filiform leaves and Mojave milkweed has much wider leaves.

Is this plant invasive?

This plant has not been shown to be invasive in the literature. It also has a fairly restrictive habitat and is uncommon in most of its range.

Gardening with Mojave Milkweed

Plant of mojave milkweed (Asclepias nyctaginifolia) in the desert.
Mojave Milkweed (Asclepias nyctaginifolia) — Mike, CC BY-SA 3.0, via Wikimedia Commons

Hardiness

This species is hardy in zones 7-9. 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 sun and has dry sandy soils.

Planting Mojave 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

  • Abrams, Le Roy and Roxana S. Ferris. 1951. An illustrated flora of the Pacific States: Washington, Oregon, and California. (Stanford University: Stanford University Press).
  • Felger, R.S., S. Rutman, and J. Malusa. 2014. Ajo Peak to Tinajas Atlas: Flora of Southwestern Arizona: Part 8, Eudicots: Acanthaceae-Apocynaceae. Phytoneuron 2014-85: 1-71.
  • Greene, Edward Lee. 1896. On the Classification of the Asclepiads. Pittonia (Berkley, CA: Doxey and Co.).
  • Grodsky, Steven M., Leslie S. Saul-Gershenz, Kara A. Moore-O’Leary, and Rebecca R. Hernandez. 2020. Her Majesty’s Desert Throne: The Ecology of Queen Butterfly Oviposition on Mojave Milkweed Plants. Insects 11 (4): 257.
  • Grodsky, Steven M., Leslie S. Saul-Gershenz, Kara A. Moore-O’Leary, Jason P. Whitney, and Rebecca R. Hernandez. 2020. Hare don’t care! Consumption of a rare, desert milkweed containing phytochemicals by the black-tailed jackrabbit. Journal of Arid Environments 174: 1.
  • McLaughlin, Steven P. 2006. Vascular Flora of Sonoita Creek State Natural Area and San Rafael State Park: Arizona’s First Natural-Area Parks. Sida 22: 661-704.
  • Southern California Academy of Sciences. 1959. Entomological Briefs – New Food Plant and Collecting Records. Bulletin of the Southern California Academy of Sciences. 58: 171.
  • Verrier, James T. 2018. Annotated Flora of the Santa Catalina Mountains, Pima and Pinal Counties, Southeastern Arizona. Desert Plants 33: 5-291.
  • 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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