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Hometown Field Guidesby Garden with Lilly

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Plate 5

Antelope horns milkweed

Asclepias asperula, an important spring host for monarchs in the southern United States (and one of the toughest for caterpillars to eat), with close-ups of the flower, its pollen clip, the pod and the sap.

Watercolor of antelope horns milkweed: sprawling stems with narrow leaves from a woody crown, two round flower balls, a curved bumpy seed pod and a thick taproot in rocky soil. Beside it, close-ups of one flower with its petals cupped upward around white hoods, purple at the base, and a central column; a dark clip holding two golden pollen bags; the same kind of clip caught on a bee's leg; an open pod packed with flat brown seeds and silky floss, and one loose seed with its parachute; a torn leaf dripping milky sap; and a leaf stalk with a notch bitten in it and a caterpillar on the leaf beyond.
  1. Flower ballLots of little flowers grow from one point, like the spokes of an umbrella. The round cluster is called an umbel.
  2. Petals cup upwardOn most milkweeds the petals fold back. On antelope horns they cup upward around the middle, like a little bowl.
  3. HoodsFive scoop-shaped hoods hold sweet nectar. Bees and wasps clamber over them to drink.
  4. Center columnThe flower's middle is one joined-up column, where the pollen parts and the seed-making parts are fused.
  5. Pollen clipMilkweed pollen isn't dust. It comes in two waxy bags hanging from a tiny clip, like saddlebags.
  6. The clipThe tiny dark knob joining the two bags is the clip. It grabs an insect's foot as the insect pulls its leg out of a slit in the flower. The flower close-up doesn't show the slits.
  7. Pollen bagsEach waxy bag is packed with pollen. Slipped into the slit of another flower, it can start that flower's seeds.
  8. Along for the rideThe clip hitches a ride on a bee's leg. Its arms twist as they dry, so the pollen bags can slip into a slit on the next flower it visits.
  9. Seed podThe curved green pod looks like an antelope's horn. That's where the name comes from!
  10. SeedsInside, flat brown seeds are packed tight, overlapping like fish scales.
  11. Silk parachuteEach seed wears a silky parachute. When the pod splits, the wind carries the seeds far away.
  12. Milky sapA torn leaf leaks white, sticky sap. Keep it out of eyes and mouths: it can hurt an eye and it's poisonous to swallow. It can also glue a tiny caterpillar's jaws shut.
  13. Caterpillar notchBig caterpillars bite a notch in the leaf stalk first. That stops the sap flowing into the part they eat.
  14. TaprootA thick root reaches deep underground. It helps the plant survive dry summers and grow new stems.

No horns here

Most milkweeds have a tiny curved horn inside each hood. Antelope horns doesn't. The "horns" in its name are the curved seed pods. Even a Texas Parks and Wildlife magazine article called the flower's star a ring of "horns."

Sources: Lady Bird Johnson Wildflower Center; Monarch Watch milkweed profiles; Native Plant Society of Texas; Hastings et al., PeerJ (2026) on latex and toxins; Dussourd & Eisner, Science (1987) on leaf-notching; MacIvor et al., Ecol. Evol. (2017) on which insects carry the pollen.

Don’t rely on a drawing alone to identify a living thing or to decide whether it is safe to touch.

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