California Milkweed
Asclepias californica Greene
A gorgeous, entirely white-woolly California endemic whose deep wine-red flowers hang in heavy nodding clusters against silver foliage. It looks like a plant designed rather than evolved.
Also called Round-hooded Milkweed.
- Height
- 1 ft–3 ft
- Spread
- 1.5 ft–3 ft
- Flowers
- maroon, purple
- Bloom
- April to July
- Light
- Full sun
- Soil moisture
- Dry
- USDA zones
- 8–10
- Leaves
- Opposite, ovate
- Sap
- Milky latex
- Roots
- Deep taproot, resents transplanting
- Stratification
- 30 days cold-moist
- Range
- 1 state
When it flowers
California Milkweed blooms April to July, peaking in May and June.
How to identify it
- Entire plant thickly felted in white wool, giving a silver-gray appearance.
- Flowers deep maroon to dusty purple-red, in large drooping clusters.
- Stems sprawl and arch outward from a woody crown.
- Chaparral, oak woodland and grassland slopes below 7,000 feet.
Unfamiliar words are in the glossary, and the identification key will narrow a plant down from what you can see.
The parts that identify it
Ecology and wildlife value
An important western monarch host in the California foothills, blooming before the summer dry season arrives.
Monarchs are not the only thing that will find it. Expect large milkweed bugs on ripening pods, oleander aphids on the stems, red milkweed beetles at the flowers and, in late summer, milkweed tussock moths. Everything that lives on milkweed.
Growing california milkweed
Superb in a dry California garden but resents summer water once dormant. Sharp drainage, full sun, and no irrigation after June.
Seed needs about 30 days of cold-moist stratification. Deep taproot, resents transplanting. See how to plant milkweed seed for the full method.
Cautions
Standard milkweed cautions. More on milkweed toxicity.
Where california milkweed grows
Recorded in 1 state: California.
County records from USDA PLANTS, public domain. Cross-check against BONAP and your regional flora before making management decisions.
References and further reading
Names, ranges and conservation status here are drawn from the databases below. Where those disagree with a regional flora, trust the flora.
- Plants of the World Online 21153-2. Royal Botanic Gardens, Kew. Accepted name, authorship and global distribution.
- GBIF 3170236. Global Biodiversity Information Facility. Aggregated occurrence records.
- iNaturalist 51272. Community observations, photographs and phenology.
- Wikipedia. General-audience article on this species.
- BONAP county distribution map. Biota of North America Program. County-level range map.
- NatureServe Explorer. Conservation status ranks at global and state level.
- World Flora Online. Nomenclature and synonymy.
- Woodson, R. E. (1954). The North American species of Asclepias L.. Annals of the Missouri Botanical Garden 41(1): 1–211. The monograph the modern taxonomy of the genus still rests on. View
- Flora of North America Editorial Committee (eds.) (2026). Flora of North America North of Mexico. Oxford University Press, New York and Oxford. Accepted names, keys and descriptions for the North American flora. View
- Royal Botanic Gardens, Kew (2026). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Nomenclature and global distribution, keyed to IPNI name identifiers. View
- Kartesz, J. T. (Biota of North America Program) (2026). North American Plant Atlas. BONAP, Chapel Hill, North Carolina. County-level distribution maps, the basis for the ranges generalized here. View
- USDA, NRCS (2026). The PLANTS Database. National Plant Data Team, Greensboro, North Carolina. State-level distribution, wetland status and nomenclature. View
- Agrawal, A. A. (2017). Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution. Princeton University Press. The standard general account of the milkweed and monarch relationship. View
Cite this page
This page is licensed CC BY 4.0. Quote it, adapt it and reuse it, including commercially, as long as you credit Milkweed USA and link back.
Milkweed USA. (2026). California Milkweed (Asclepias californica). Retrieved DATE, from https://milkweedusa.com/species/california-milkweed/
"California Milkweed (Asclepias californica)." Milkweed USA, 2026, https://milkweedusa.com/species/california-milkweed/. Accessed DATE.
Milkweed USA. "California Milkweed (Asclepias californica)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/california-milkweed/.
@misc{milkweedusa_speciescaliforniamilkweed,
title = {California Milkweed (Asclepias californica)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/species/california-milkweed/},
note = {Accessed DATE}
}