# Serpentine Milkweed (Asclepias solanoana)

> A prostrate northern California endemic confined to serpentine barrens, forming flat mats of round gray-green leaves studded with small cream flowers. It grows on soil so metal-rich that almost nothing else survives.

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

## Summary

A prostrate northern California endemic confined to serpentine barrens, forming flat mats of round gray-green leaves studded with small cream flowers. It grows on soil so metal-rich that almost nothing else survives.

## Key facts

| Field | Value |
| --- | --- |
| Scientific name | Asclepias solanoana Woodson |
| Genus | Asclepias |
| Family | Apocynaceae |
| Common names | Serpentine Milkweed, Solano Milkweed |
| Status | Native; rare or legally protected in part of its range |
| Height | 4 in–10 in |
| Spread | 1 ft–2 ft |
| Flower color | cream, pink |
| Bloom period | May to July |
| Light | Full sun |
| Soil moisture | Dry |
| USDA zones | 7-9 |
| Leaf arrangement | opposite |
| Leaf shape | orbicular |
| Sap | Milky latex |
| Root system | Deep taproot, resents transplanting |
| Seed stratification | 60 days cold-moist |
| Monarch value (0-5) | 1 |
| Garden value (0-5) | 1 |
| Nectar value (0-5) | 2 |
| US states recorded | California |

## Identification

- Completely prostrate mats on bare serpentine rock and soil.
- Round, thick, gray-green leaves pressed to the ground.
- Small cream flowers with pinkish hoods.

## Ecology

A serpentine-endemic rarity of high conservation value and very limited distribution.

## Growing

Should not be collected or cultivated from wild material.

## Cautions

Rare California endemic; leave undisturbed.

## References

- Plants of the World Online: https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:290390-2
- GBIF: https://www.gbif.org/species/3170277
- iNaturalist: https://www.inaturalist.org/taxa/62293
- Wikipedia: https://en.wikipedia.org/wiki/Asclepias_solanoana
- BONAP county map: https://bonap.net/MapGallery/County/Asclepias%20solanoana.png
- NatureServe: https://explorer.natureserve.org/Search?searchTerm=Asclepias%20solanoana

## Photographs

- Asclepias solanoana (Shasta-Trinity National Forest USDA Forest Service., CC0): https://commons.wikimedia.org/wiki/File:Asclepias_solanoana.jpeg
- Serpentine Milkweed photographed in California, US (Don Loarie, CC BY 4.0): https://www.inaturalist.org/observations/6474783
- Serpentine Milkweed photographed in Mendocino National Forest, US-CA, US (Public domain (CC0), CC0): https://www.inaturalist.org/observations/6726146
- Serpentine Milkweed photographed in Trinity County, US-CA, US (Dee Shea Himes, CC BY 4.0): https://www.inaturalist.org/observations/70509360
- Serpentine Milkweed photographed in California, US (Trevor Van Loon, CC BY 4.0): https://www.inaturalist.org/observations/219453414
- Serpentine Milkweed photographed in Sonoma County, US-CA, US (Roger Raiche, CC BY 4.0): https://www.inaturalist.org/observations/80324534
- Serpentine Milkweed photographed in Trinity County, US-CA, US (Matt Berger, CC BY 4.0): https://www.inaturalist.org/observations/122385606
- Serpentine Milkweed photographed in California, US (Steve Matson, CC BY 4.0): https://www.inaturalist.org/observations/52876286

## How to cite

Milkweed USA. (2026). Serpentine Milkweed (Asclepias solanoana). https://milkweedusa.com/species/serpentine-milkweed/