Sonchus arvensis

Perennial Sow Thistle

Erect, with both flowering and nonflowering stems. Milky sap. Leaves entire to pinnately lobed; lower leaves 3–6 in., with short petioles. Upper leaf edges with thorny teeth, clasping stems; lowest lobes extend beyond stem and curl. Flower stalks much divided, leafless. Flower heads 1–2 in. across, containing yellow ray-like disk flowers. Many flower heads produced, with some going to seed, others coming into bloom all summer. Grows in wet to damp soils. Noxious weed. Common sow thistle, S. oleraceus, has pointed tips on the basal, clasping lobes that are not curled or coiled. Prickly sow thistle, S. asper, has coarse teeth on the sometimes lobed, clasping leaves with the basal lobes curled tight to stem.

  • Rarity: Locally Common
  • Flowering Time: All Summer
  • Life Cycle: Perennial
  • Height: 15--60 inches
  • Habitat: Coastal, Meadow, Disturbed
  • Found In: Olympic NP, Steens, N Cascades NP
  • Native: No