# Wheel Milkweed (Asclepias uncialis)

> 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.

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

## Summary

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.

## Key facts

| Field | Value |
| --- | --- |
| Scientific name | Asclepias uncialis Greene |
| Genus | Asclepias |
| Family | Apocynaceae |
| Common names | Wheel Milkweed, Dwarf Milkweed, Greene’s Milkweed |
| Status | Native; rare or legally protected in part of its range |
| Height | 2 in–6 in |
| Spread | 4 in–1 ft |
| Flower color | maroon, green |
| Bloom period | April to June |
| Light | Full sun |
| Soil moisture | Dry |
| USDA zones | 4-8 |
| Leaf arrangement | opposite |
| Leaf shape | narrow |
| 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 | Arizona, Colorado, Kansas, New Mexico, Nevada, Utah, Wyoming |

## Identification

- 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

Poorly understood. Habitat loss to cultivation and energy development is the principal threat; report sightings to your state natural heritage program.

## Growing

Do not attempt to collect. This species should be left entirely alone in the wild.

## Cautions

Rare and legally protected in parts of its range. Photograph, record and leave it.

## References

- Plants of the World Online: https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:94711-1
- GBIF: https://www.gbif.org/species/3170289
- iNaturalist: https://www.inaturalist.org/taxa/126674
- Wikipedia: https://en.wikipedia.org/wiki/Asclepias_uncialis
- BONAP county map: https://bonap.net/MapGallery/County/Asclepias%20uncialis.png
- NatureServe: https://explorer.natureserve.org/Search?searchTerm=Asclepias%20uncialis

## Photographs

- Asclepias uncialis lg (Steve Olson, Public domain): https://commons.wikimedia.org/wiki/File:Asclepias_uncialis_lg.jpg
- Asclepias uncialis - Flickr - aspidoscelis (Patrick Alexander from Las Cruces, NM, CC0): https://commons.wikimedia.org/wiki/File:Asclepias_uncialis_-_Flickr_-_aspidoscelis.jpg
- Asclepias uncialis - Flickr - aspidoscelis (1) (Patrick Alexander from Las Cruces, NM, CC0): https://commons.wikimedia.org/wiki/File:Asclepias_uncialis_-_Flickr_-_aspidoscelis_(1).jpg
- Wheel Milkweed photographed in 33.169 -108.748 (Public domain (CC0), CC0): https://www.inaturalist.org/observations/9259239
- Wheel Milkweed photographed in Grant County, US-NM, US (Andrew Tree, CC BY 4.0): https://www.inaturalist.org/observations/207193553
- Wheel Milkweed photographed in Placitas, NM 87043, USA (Eric Knight, CC BY 4.0): https://www.inaturalist.org/observations/212004205

## How to cite

Milkweed USA. (2026). Wheel Milkweed (Asclepias uncialis). https://milkweedusa.com/species/wheel-milkweed/