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Sonchus asper
Sonchus asper  (Spiny Sow-thistle)
Asteraceae (Sunflower Family)

Moist meadows, disturbed sites, openings. Spring, summer, fall.
Lewis, Colorado, September 1, 2017.

This wide-spread (see the map below) non-native, annual grows to over three feet tall, often with multiple stems.

The plant is native to Europe. The genus was named by Linnaeus in 1753 from specimens collected in Europe and Linnaeus named the species, Sonchus oleraceus var. asper. John Hill renamed the plant Sonchus asper in 1769.

"Sonchus" is Greek for "thistle" and "asper" is Latin for "rough", referring to the very spiny leaves.

Sonchus asper

Sonchus asper

Sonchus asper  (Spiny Sow-thistle)
Asteraceae (Sunflower Family)

Moist meadows, disturbed sites, openings. Spring, summer, fall.
Lewis, Colorado, September 1, 2017.

Flowers are yellow and flower heads contain only ray flowers (as do Taraxacum, Dandelions). The shape of the involucre after flowering is distinctive and contrasts with the shape of the buds.

 

Sonchus asper

Sonchus asper  (Spiny Sow-thistle)
Asteraceae (Sunflower Family)

Moist meadows, disturbed sites, openings. Spring, summer, fall.
Lewis, Colorado, September 1, 2017.

Leaves may be entire to more commonly deeply lobed to pinnatifid, and they are a very spiny mass. Leaves clasp the stem and have circular ear-like lobes (in red). The shape of the lobes is a key characteristic separating this species from Sonchus oleraceus which has acute rather than rounded leaf auricles.

               Sonchus asper

Sonchus asper

Sonchus asper

Sonchus asper  (Spiny Sow-thistle)
Asteraceae (Sunflower Family)

Moist meadows, disturbed sites, openings. Spring, summer, fall.
Lewis, Colorado, September 1, 2017.

Stems are hollow and may be smooth ("glabrous"), hairy, or glandular. Those shown here are glabrous.

Stems are commonly single. Multiple stems often result from mowing or grazing.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Sonchus asper

Range map for Sonchus asper