# Prostrate Milkweed (Asclepias prostrata)

> A federally endangered milkweed known from a few sites in the south Texas brush country, growing completely flat against gravelly ground with small greenish-white flowers. It was listed under the Endangered Species Act in 2023.

Source: https://milkweedusa.com/species/prostrate-milkweed/  
Licence: CC BY 4.0 (Milkweed USA)

## Summary

A federally endangered milkweed known from a few sites in the south Texas brush country, growing completely flat against gravelly ground with small greenish-white flowers. It was listed under the Endangered Species Act in 2023.

## Key facts

| Field | Value |
| --- | --- |
| Scientific name | Asclepias prostrata W.H. Blackwell |
| Genus | Asclepias |
| Family | Apocynaceae |
| Common names | Prostrate Milkweed |
| Status | Native; rare or legally protected in part of its range |
| Height | 2 in–6 in |
| Spread | 8 in–1.7 ft |
| Flower color | green, white |
| Bloom period | March to September |
| Light | Full sun |
| Soil moisture | Dry |
| USDA zones | 8-10 |
| Leaf arrangement | opposite |
| Leaf shape | narrow |
| Sap | Milky latex |
| Root system | Deep taproot, resents transplanting |
| Seed stratification | 30 days cold-moist |
| Monarch value (0-5) | 2 |
| Garden value (0-5) | 1 |
| Nectar value (0-5) | 2 |
| US states recorded | Texas |

## Identification

- Entirely prostrate, with stems lying flat on bare gravelly soil.
- Small narrow opposite leaves and tiny greenish-white flowers.
- Known only from Starr and Zapata counties in south Texas and adjacent Mexico.

## Ecology

Threatened by brush clearing, energy development and border infrastructure. Most surviving populations are tiny.

## Growing

Federally endangered. Collection is prohibited; report sightings to Texas Parks and Wildlife.

## Cautions

Listed as Endangered under the US Endangered Species Act.

## References

- Plants of the World Online: https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:21269-2
- GBIF: https://www.gbif.org/species/3170330
- iNaturalist: https://www.inaturalist.org/taxa/158755
- Wikipedia: https://en.wikipedia.org/wiki/Asclepias_prostrata
- BONAP county map: https://bonap.net/MapGallery/County/Asclepias%20prostrata.png
- NatureServe: https://explorer.natureserve.org/Search?searchTerm=Asclepias%20prostrata

## Photographs

- Asclepias prostrata in habitat (Sam Kieschnick, CC BY 4.0): https://commons.wikimedia.org/wiki/File:Asclepias_prostrata_in_habitat.jpg
- Closeup of Asclepias prostrata in flower (Sam Kieschnick, CC BY 4.0): https://commons.wikimedia.org/wiki/File:Closeup_of_Asclepias_prostrata_in_flower.jpg
- Prostrate Milkweed photographed in Texas, US (Matt Berger, CC BY 4.0): https://www.inaturalist.org/observations/71035195
- Prostrate Milkweed photographed in Texas, US (Eric Knight, CC BY 4.0): https://www.inaturalist.org/observations/44713620
- Prostrate Milkweed photographed in Texas, US (Reid Hardin, CC BY 4.0): https://www.inaturalist.org/observations/85386280
- Prostrate Milkweed photographed in Texas, US (Turner Brockman, CC BY-SA 4.0): https://www.inaturalist.org/observations/304856514
- Prostrate Milkweed photographed in Texas, US (Joseph Aubert, CC BY 4.0): https://www.inaturalist.org/observations/232205838
- Prostrate Milkweed photographed in Texas, US (Michelle W. （鍾偉瑋）, CC BY 4.0): https://www.inaturalist.org/observations/123192027

## How to cite

Milkweed USA. (2026). Prostrate Milkweed (Asclepias prostrata). https://milkweedusa.com/species/prostrate-milkweed/