Bloomipedia
Antelopehorn milkweed (Asclepias asperula)
Photo: Michelle W. （鍾偉瑋） via iNaturalist · CC BY 4.0 · resized

Flower profile

Antelopehorn milkweed

Asclepias asperula

Native in the lower 48

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.

11states
2of our state lists
29,255U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: Texas, Utah

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 109 flowers on our Texas list. iNaturalist
  • iNaturalist has 1,312 research-grade sightings of it in Utah, ranking #38 among the 109 flowers on our Utah list. iNaturalist

Antelopehorn milkweed gift ideas

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When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (3,305 records)
Bloom time in each of our 2 states
StateTypePeak bloomSightings*
TexasNativeApril–May24,514
UtahNativeMay–July1,312

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?

For peopleNot well documented

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.

For petsToxic to dogs, cats and horses

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.

More Texas flowers

Green antelopehorns (Asclepias viridis)

Green antelopehorns

Asclepias viridis

Native

🌼 Blooms in TX: April–September
Showy milkweed (Asclepias speciosa)

Showy milkweed

Asclepias speciosa

Native

🌼 Blooms: June–August
Zizotes milkweed (Asclepias oenotheroides)

Zizotes milkweed

Asclepias oenotheroides

Native

🌼 Blooms in TX: April–October

Sources