MilkweedUSA

Native Subspecies of Antelope Horns

Western Antelope Horns

Asclepias asperula subsp. asperula (Decne.) Woodson

The western antelope horns, of mountain and mesa country from the Great Basin to the Trans-Pecos, and south in Mexico as far as Oaxaca.

Also called Spider Milkweed.

How to tell it apart

Leaves are narrower, almost linear, and longer, to 17 cm. The flower stalk is long, up to 22 cm, and the pods are smooth rather than warty. Crown segments are reddish-purple with a white upper edge.

Compare with subsp. capricornu. Everything else about the plant, including how to grow it and what it is worth to monarchs, is on the antelope horns page.

Where it grows

A high-country plant, 700 to 2,800 m. Within the United States it only just reaches California, Idaho and Oklahoma, each at a single county, and in Texas it is confined to the Trans-Pecos.

Alaska: not recorded Maine: not recorded Vermont: not recorded New Hampshire: not recorded Washington: not recorded Idaho: recorded Montana: not recorded North Dakota: not recorded Minnesota: not recorded Illinois: not recorded Wisconsin: not recorded Michigan: not recorded New York: not recorded Massachusetts: not recorded Rhode Island: not recorded Oregon: not recorded Nevada: recorded Wyoming: not recorded South Dakota: not recorded Iowa: not recorded Indiana: not recorded Ohio: not recorded Pennsylvania: not recorded New Jersey: not recorded Connecticut: not recorded California: recorded Utah: recorded Colorado: recorded Nebraska: not recorded Missouri: not recorded Kentucky: not recorded West Virginia: not recorded Virginia: not recorded Maryland: not recorded Delaware: not recorded Arizona: recorded New Mexico: recorded Kansas: not recorded Arkansas: not recorded Tennessee: not recorded North Carolina: not recorded South Carolina: not recorded District of Columbia: not recorded Texas: recorded Oklahoma: recorded Louisiana: not recorded Mississippi: not recorded Alabama: not recorded Georgia: not recorded Hawaii: not recorded Florida: not recorded
Recorded in 9 states. Shading is generalized to whole states.

Distribution follows the Flora of North America treatment, United States only. Antelope Horns as a whole is recorded in 11 states.

Flowering

Western Antelope Horns blooms March to September, peaking in April and May. Plants reach 8 in–2 ft.

Other names

This plant has also been published as Asclepias capricornu subsp. occidentalis. Those names refer to the same taxon and you will meet them in older floras and in some databases.

References

The description, distribution and synonymy here follow Mark Fishbein’s treatment of Asclepias in Flora of North America vol. 14 (2023).

Cite this page

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APA Milkweed USA. (2026). Western Antelope Horns (Asclepias asperula subsp. asperula). Retrieved DATE, from https://milkweedusa.com/species/antelope-horns/asperula/
MLA "Western Antelope Horns (Asclepias asperula subsp. asperula)." Milkweed USA, 2026, https://milkweedusa.com/species/antelope-horns/asperula/. Accessed DATE.
Chicago Milkweed USA. "Western Antelope Horns (Asclepias asperula subsp. asperula)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/antelope-horns/asperula/.
BibTeX @misc{milkweedusa_speciesantelopehornsasperula, title = {Western Antelope Horns (Asclepias asperula subsp. asperula)}, author = {{Milkweed USA}}, year = {2026}, url = {https://milkweedusa.com/species/antelope-horns/asperula/}, note = {Accessed DATE} }