Wheel Milkweed
Asclepias uncialis Greene
One of the rarest and smallest milkweeds in North America, a two-inch-high scatter of maroon-tinged flowers on the shortgrass steppe, tracked as a species of concern in several states including Colorado.
Also called Dwarf Milkweed, Greene’s Milkweed.
- Height
- 2 in–6 in
- Spread
- 4 in–1 ft
- Flowers
- maroon, green
- Bloom
- April to June
- Light
- Full sun
- Soil moisture
- Dry
- USDA zones
- 4–8
- Leaves
- Opposite, narrow
- Sap
- Milky latex
- Roots
- Deep taproot, resents transplanting
- Stratification
- 60 days cold-moist
- Range
- 7 states
When it flowers
Wheel Milkweed blooms April to June, peaking in May.
How to identify it
- Minute: frequently no taller than a golf tee, easily overlooked among grass.
- Flowers dull maroon and green, held just above the soil.
- Appears briefly in spring then disappears.
Ecology and wildlife value
Poorly understood. Habitat loss to cultivation and energy development is the principal threat; report sightings to your state natural heritage program.
Growing wheel milkweed
Do not attempt to collect. This species should be left entirely alone in the wild.
Seed needs about 60 days of cold-moist stratification. Deep taproot, resents transplanting. See how to plant milkweed seed for the full method.
Cautions
Rare and legally protected in parts of its range. Photograph, record and leave it. More on milkweed toxicity.
Where wheel milkweed grows
Recorded in 7 states: Arizona, Colorado, Kansas, New Mexico, Nevada, Utah, Wyoming.
Distribution is generalized to state level. For county-level maps see USDA PLANTS and BONAP.
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 94711-1. Royal Botanic Gardens, Kew. Accepted name, authorship and global distribution.
- GBIF 3170289. Global Biodiversity Information Facility. Aggregated occurrence records.
- iNaturalist 126674. 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
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Milkweed USA. (2026). Wheel Milkweed (Asclepias uncialis). Retrieved DATE, from https://milkweedusa.com/species/wheel-milkweed/
"Wheel Milkweed (Asclepias uncialis)." Milkweed USA, 2026, https://milkweedusa.com/species/wheel-milkweed/. Accessed DATE.
Milkweed USA. "Wheel Milkweed (Asclepias uncialis)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/wheel-milkweed/.
@misc{milkweedusa_specieswheelmilkweed,
title = {Wheel Milkweed (Asclepias uncialis)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/species/wheel-milkweed/},
note = {Accessed DATE}
}