Summary ⁷

Asclepias subverticillata (horsetail milkweed) is a plant indigenous to the southwestern United States. It is an important nectar source for several insects but has poisonous properties to livestock.

Botanical Information ⁸

Horsetail milkweed grows in North America. It belongs to the milkweed family. Its scientific name is Asclepias subverticillata and it is a flowering plant. Its other common names are whorled milkweed or narrowleaf milkweed. When blooming from June to September, it looks like white round stars on top of a green stem. The leaves are narrow, growing from the stem in a whorled pattern.

Ecological Information ⁹

Horsetail milkweed grows on sandy plains and mesas and is common along roadsides. Milkweeds, including horsetail milkweed, are the primary hosts for Monarch butterfly larva. Milkweed habitats are being destroyed by land development, agricultural intensification, and the increase in the use of herbicide-resistant crops. It is important to conserve land where milkweeds grow to save the population of monarch butterflies from going extinct.

Ethnobotanical Information ¹⁰

This plant is medicinal. It stops nose bleeds and reduces coughing. According to ethnobotanical reports, the Hopi used horsetail milkweed as a "galactagogue" to increase the flow of a new mother's milk. (Note: Such reports often lack important contextual information and relevant traditional ecological knowledge.) Milkweed can be toxic, especially the narrow-leaf species. It is not recommended to ingest this narrowleaf milkweed.

References ¹¹

www.plants.usda.gov
https://www.wildflower.org/plants/result.php?id_plant=ASSU2
Nabhan, Buckley and Dial. (2015). Pollinator Plants of the Desert Southwest.
https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/azpmctn12744.pdf

About the Author ¹²

Student author(s)*: Daniel (age 12) and Ric (age 13) from South Valley Academy

*The entries in this field guide have been edited by Yerba Mansa Project staff to ensure that they contain quality, fact-checked content and standardized formatting. https://yerbamansaproject.org/

Sources and Credits

1. (c) Josh*m, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/gravitywave/7370132048/
2. (c) Jerry Oldenettel, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/jroldenettel/5201738834/
3. (c) Carolannie--slow return, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/carolannie/4845218852/
4. (c) Jerry Oldenettel, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/jroldenettel/4968599869/
5. (c) Anthony Mendoza, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/39039456@N07/9667010203/
6. (c) Elizabeth Sellers, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/esellers/8091555001/
7. Adapted by caseynm from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Asclepias_subverticillata
8. Adapted by albuquerqueherbalism from a work by (c) kristen_himm, some rights reserved (CC BY-SA)
9. Adapted by Hannah from a work by (c) kristen_himm, some rights reserved (CC BY-SA)
10. Adapted by albuquerqueherbalism from a work by (c) smiller33, some rights reserved (CC BY-SA)
11. Adapted by Hannah from a work by (c) caseynm, some rights reserved (CC BY-SA)
12. Adapted by albuquerqueherbalism from a work by (c) caseynm, some rights reserved (CC BY-SA)

More Info

• iNat taxon page
• Biodiversity Heritage Library
• BOLD Systems BIN search
• eFloras.org
• Flora of North America (beta)
• Global Biodiversity Information Facility (GBIF)
• HOSTS - a Database of the World's Lepidopteran Hostplants
• IPNI (with links to POWO, WFO, and BHL)
• NatureServe Explorer 2.0
• SEINet Symbiota portals
• Tropicos
• USDA PLANTS database
• World Flora Online

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