# Antelope Horns (Asclepias asperula)

> A low, sprawling clump of arching stems topped by softball-sized globes of green flowers with maroon centers, blooming very early on limestone and caliche soils. In Texas and New Mexico it is the plant that meets the first northbound monarchs of the year.

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

## Summary

A low, sprawling clump of arching stems topped by softball-sized globes of green flowers with maroon centers, blooming very early on limestone and caliche soils. In Texas and New Mexico it is the plant that meets the first northbound monarchs of the year.

## Key facts

| Field | Value |
| --- | --- |
| Scientific name | Asclepias asperula (Decne.) Woodson |
| Genus | Asclepias |
| Family | Apocynaceae |
| Common names | Antelope Horns, Spider Milkweed, Green-flowered Milkweed |
| Status | Native |
| Height | 1 ft–2 ft |
| Spread | 1.5 ft–3 ft |
| Flower color | green, cream, maroon |
| Bloom period | March to July |
| Light | Full sun |
| Soil moisture | Dry |
| USDA zones | 5-9 |
| Leaf arrangement | alternate |
| Leaf shape | narrow |
| Sap | Milky latex |
| Root system | Deep taproot, resents transplanting |
| Seed stratification | 30 days cold-moist |
| Monarch value (0-5) | 5 |
| Garden value (0-5) | 3 |
| Nectar value (0-5) | 3 |
| US states recorded | Arizona, Colorado, Kansas, Nebraska, New Mexico, Nevada, Oklahoma, Texas, Utah |

## Identification

- Flowers in tight spherical clusters, pale green with dark red-purple hoods. No other milkweed in its range looks like this.
- Stems sprawl outward and curve upward rather than standing straight.
- Leaves are long, narrow and often folded lengthwise along the midrib.
- Curved, upward-pointing pods gave the plant its name.

## Ecology

Critically timed rather than merely abundant: it is in full leaf in March and April when monarchs arrive in Texas from Mexico, making it a keystone host for the first generation of the year. Also heavily used by queen butterflies.

## Growing

Demands lean, alkaline, sharply drained soil and full sun; it rots quickly in rich beds or irrigated lawns. Direct-sow into gravelly ground, because the taproot resents transplanting. Goes dormant by late summer.

## Cautions

One of the more toxic species to livestock, historically responsible for sheep losses on overgrazed range.

## Questions

**When do antelope horns bloom in Texas?**

Typically March through May, with a possible second flush after summer rain. That early bloom is what makes it so important to the first northbound monarch generation.

## References

- Plants of the World Online: https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:21143-2
- GBIF: https://www.gbif.org/species/8683730
- iNaturalist: https://www.inaturalist.org/taxa/62298
- Wikipedia: https://en.wikipedia.org/wiki/Asclepias_asperula
- BONAP county map: https://bonap.net/MapGallery/County/Asclepias%20asperula.png
- NatureServe: https://explorer.natureserve.org/Search?searchTerm=Asclepias%20asperula

## Photographs

- Asclepias asperula - Antelope Horns (Wing-Chi Poon, CC BY-SA 2.5): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_-_Antelope_Horns.jpg
- Asclepias asperula 1 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_1.jpg
- Asclepias asperula 2 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_2.jpg
- Asclepias asperula 3 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_3.jpg
- Asclepias asperula 4 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_4.jpg
- Asclepias asperula 5 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_5.jpg
- Asclepias asperula 6 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_6.jpg
- Asclepias asperula 9 (Stan Shebs, CC BY-SA 3.0): https://commons.wikimedia.org/wiki/File:Asclepias_asperula_9.jpg

## How to cite

Milkweed USA. (2026). Antelope Horns (Asclepias asperula). https://milkweedusa.com/species/antelope-horns/