Flower profile
Antelopehorn milkweed
Asclepias asperula
Antelopehorn milkweed (Asclepias asperula) is a flowering plant in the Apocynaceae family, native in the lower 48 states, blooming mostly April–June across the U.S.
Antelopehorn milkweed is a wildflower that USDA PLANTS lists as native in the lower 48 states. It's on our flower lists for 2 states, and across the U.S. it's most often seen in bloom in April–June.
*iNaturalist research-grade observations, as of October 17, 2026.
Quick look
Asclepias asperula, commonly called antelope horns milkweed or spider milkweed, is a species of milkweed native to the Southwestern United States and northern Mexico.
- It belongs to the Apocynaceae family. iNaturalist
- USDA PLANTS describes it as an herb (forb) with a perennial life cycle. USDA PLANTS
- USDA PLANTS lists it as native in the lower 48 states and records it in 11 states. USDA PLANTS
- NatureServe lists it as native to Texas and Utah. NatureServe
- In Texas, most iNaturalist sightings of it in flower come in April–May. iNaturalist
- In Utah, most iNaturalist sightings of it in flower come in May–July. iNaturalist
- iNaturalist has 24,514 research-grade sightings of it in Texas, ranking #10 among the 169 flowers on our Texas list. iNaturalist
- iNaturalist has 1,312 research-grade sightings of it in Utah, ranking #38 among the 153 flowers on our Utah list. iNaturalist
When does it bloom?
Conservation status
- Federal (U.S. ESA)
- Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. USFWS ECOS
- NatureServe global
- G5 Secure worldwide. NatureServe
- Texas
- Not listed Not on Texas endangered and threatened plants (31 Tex. Admin. Code § 69.8), as listed by Texas Parks and Wildlife. NatureServe: SNR, not yet ranked in Texas. 31 TAC 69.8
- Utah
- No list Utah has no state law listing endangered or threatened plants, so we show NatureServe's Utah ranks instead. NatureServe: SNR, not yet ranked in Utah.
- Rare elsewhere
- Other states where NatureServe ranks it rare or missing: ID (S1). (S1 critically imperiled, S2 imperiled, SH possibly extirpated, SX presumed extirpated.)
Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.
Can you eat it?
None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.
ASPCA's entry “Milkweed” (Asclepias species), which covers the whole genus, lists it as toxic to dogs, cats and horses. Signs include: Vomiting, profound depression, weakness, anorexia, and diarrhea are common; may be followed by seizures, difficulty breathing, rapid, weak pulse, dilated pupils, kidney or liver failure, coma… ASPCA
🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.
Where does it grow?
USDA PLANTS records antelopehorn milkweed in 11 states.
recorded by USDA PLANTS on our state lists not recorded
See the full list of states
Arizona, California, Colorado, Idaho, Kansas, Nebraska, Nevada, New Mexico, Oklahoma, Texas, Utah.
Texas counties with USDA records: Anderson, Andrews, Aransas, Bandera, Bastrop, Bell, Blanco, Bosque, Brewster, Brown, Burnet, Caldwell, Callahan, Carson, Castro, Childress, Coleman, Collingsworth, Comal, Comanche, Cooke, Coryell, Crockett, Culberson, Dallas, DeWitt, Denton, Donley, Eastland, Edwards, El Paso, Erath, Fayette, Garza, Gillespie, Goliad, Gonzales, Grayson, Hamilton, Hardeman, Harris, Hays, Hood, Hudspeth, Irion, Jackson, Jeff Davis, Jim Wells, Johnson, Jones, Karnes, Kendall, Kerr, Kimble, Llano, Lubbock, McLennan, Oldham, Parker, Pecos, Presidio, Reeves, San Patricio, San Saba, Schleicher, Scurry, Shackelford, Stephens, Sutton, Tarrant, Taylor, Terrell, Travis, Val Verde, Washington, Williamson, Wise.
Utah counties with USDA records: Beaver, Box Elder, Cache, Daggett, Davis, Garfield, Grand, Iron, Juab, Kane, Millard, Salt Lake, San Juan, Sevier, Tooele, Uintah, Utah, Washington, Wayne.
Names, range and relatives
County records: USDA PLANTS lists it in 203 counties across 10 states; the most are in Texas (77), Oklahoma (31), Kansas (23).
Other Asclepias on Bloomipedia (16): Common milkweed, Butterfly milkweed, Swamp milkweed, Green antelopehorns, Showy milkweed, Narrowleaf milkweed, Green comet milkweed, Zizotes milkweed, Tropical milkweed, Redring milkweed.
More from the Apocynaceae family (28 on Bloomipedia; most observed first): Lesser periwinkle, Greater periwinkle, Spreading dogbane, Pearl milkweed, Madagascar periwinkle, Honey-vine climbing milkweed, Hartweg's climbing milkweed, Oleander.
More Texas flowers
Sources
- USDA, NRCS. PLANTS Database, profile ASAS.
- iNaturalist, Asclepias asperula: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
- Wikipedia, Asclepias asperula (lead quoted under CC BY-SA 4.0).
- Texas: Texas endangered and threatened plants (31 Tex. Admin. Code § 69.8), as listed by Texas Parks and Wildlife.
- Texas: Texas noxious and invasive plant list (4 Tex. Admin. Code § 19.300(a)).
- Utah: Utah noxious weed list (Utah Admin. Code R68-9-3).
- USFWS, ECOS species database (ESA listing check), October 17, 2026.
- NatureServe Explorer, Asclepias asperula (global and state ranks).
- Edibility and toxicity: ASPCA.
- Photo: Michelle W. （鍾偉瑋） via iNaturalist · CC BY 4.0 · resized.