Asclepias verticillata, commonly called whorled milkweed or horsetail milkweed, is a slender perennial in the milkweed family native to much of North America. It is recognizable for its threadlike stems and narrow leaves arranged in regular whorls. Plants typically reach about 0.3–0.9 m (1–3 ft) and produce clusters of small, white to pale green flowers in summer. As with other members of the genus, stems and leaves contain a characteristic milky sap.

Identification and botanical features

Key characteristics include:

  • Opposite or whorled linear leaves, usually several per node rather than broad blades.
  • Thin, often branched stems that give a delicate, horsetail-like appearance.
  • Umbel-like clusters of tiny, five-parted flowers that are cream to greenish-white.
  • Follicles (seed pods) that split open when mature to release seeds attached to silky floss.

For broader context about the group it belongs to see the milkweed genus. Detailed regional floras and keys can be consulted through resources such as North American plant guides.

Habitat and distribution

Whorled milkweed grows in dry, well-drained sites: prairies, open woodlands, roadside margins and fields. It prefers sunny to partly shaded situations and tolerates poorer, sandy soils better than many broadleaf milkweeds. Observations and range maps are available through many conservation and natural history portals (blooming period records and local inventories often list summer flowering times).

Ecology and human uses

Asclepias verticillata plays a role in native ecosystems as a nectar source for pollinators and as a larval host for butterflies, including monarchs. Its seeds bear the silky floss historically collected from milkweed pods for stuffing and insulation. Some Indigenous and early settler traditions recorded medicinal or practical uses of various milkweeds; specifics vary by culture and species, and modern foraging or use should be approached cautiously and with reliable guidance.

Safety, management and notable facts

Milkweeds contain cardiac-active compounds (cardenolides) that can be toxic to livestock and humans if ingested in quantity; this chemical protection is also the basis for monarch caterpillars’ defensive qualities. In landscaping, whorled milkweed is sometimes chosen for native plant gardens for its tidy habit and pollinator value. For conservation status and local management recommendations consult regional databases and plant conservation groups (habitat notes, prairie restoration guides, species profiles).