Hall’s Milkweed
Asclepias hallii A. Gray
A handsome southern Rocky Mountain endemic with soft pink-mauve flower clusters and grayish lance-shaped leaves, growing on dry mesas, sandy foothills and piñon-juniper edges from Colorado to Nevada.
Also called Purple Silkweed.
- Height
- 1.5 ft–3 ft
- Spread
- 1.5 ft–3 ft
- Flowers
- pink, mauve
- Bloom
- June to August
- Light
- Full sun
- Soil moisture
- Dry
- USDA zones
- 4–8
- Leaves
- Opposite, lanceolate
- Sap
- Milky latex
- Roots
- Rhizomatous, spreads by root
- Stratification
- 30 days cold-moist
- Range
- 6 states
When it flowers
Hall’s Milkweed blooms June to August, peaking in July.
How to identify it
- Resembles a slimmer, drier-country showy milkweed with narrower leaves and smaller flowers.
- Flower clusters are terminal and upright, pale pink to dull rose.
- Stems often several from a spreading rootstock, sometimes forming loose colonies.
Unfamiliar words are in the glossary, and the identification key will narrow a plant down from what you can see.
Ecology and wildlife value
A significant monarch host on Colorado’s Western Slope and across the Colorado Plateau, where large-leaved milkweeds are scarce.
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. The flowers are a heavy nectar source, so bumble bees and large wasps work them hard, and they are the ones that actually move the pollen. Everything that lives on milkweed.
Growing hall’s milkweed
Excellent for xeric gardens in the Interior West, though seed is hard to source. Needs sharp drainage and full sun.
Seed needs about 30 days of cold-moist stratification. Rhizomatous, spreads by root. See how to plant milkweed seed for the full method.
Cautions
Standard milkweed cautions. More on milkweed toxicity.
Where hall’s milkweed grows
Recorded in 6 states: Arizona, Colorado, New Mexico, Nevada, Utah, Wyoming.
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 94337-1. Royal Botanic Gardens, Kew. Accepted name, authorship and global distribution.
- GBIF 3170237. Global Biodiversity Information Facility. Aggregated occurrence records.
- iNaturalist 158741. Community observations, photographs and phenology.
- 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
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Milkweed USA. (2026). Hall’s Milkweed (Asclepias hallii). Retrieved DATE, from https://milkweedusa.com/species/halls-milkweed/
"Hall’s Milkweed (Asclepias hallii)." Milkweed USA, 2026, https://milkweedusa.com/species/halls-milkweed/. Accessed DATE.
Milkweed USA. "Hall’s Milkweed (Asclepias hallii)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/halls-milkweed/.
@misc{milkweedusa_specieshallsmilkweed,
title = {Hall’s Milkweed (Asclepias hallii)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/species/halls-milkweed/},
note = {Accessed DATE}
}