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Integrated Crop Management
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Spiny sowthistle

Spiny sowthistle - Sonchus asper (L.) Hill

Family: Asteraceae (Composite family)
Life cycle: Annual
Native status: Introduced to N. America
Habitat: Waste areas

General description: Initially forms a basal rosette of leaves, the stem elongates into an erect, unbranched plant. Leaves are glossy, variably lobed or toothed with prickly margins, with a rounded auricle clasping the stem. Stem emits a milky sap. Produces clusters of yellow composite flowers that have a seed attached to a feathery pappus.

Key ID traits: Glossy leaves with rounded, clasping auricles.

Similar species: There are numerous wind-dispersed members of the Asteracea family that have similar growth habits that appear in disturbed habitats. Annual sowthistle is slightly taller than spiny sowthistle and has pointed auricles. Prickly lettuce has spines on the underside of the mid-vein. 

Miscellaneous: The sowthistles are not aggressive plants, but are frequently found in disturbed areas, and the seedheads filled with pappus attract people’s attention.sowthistle

leaves are glabrous with spiny leaf margins
Leaves are glabrous with spiny leaf margins
rounded auricles are the distinctive trait of spiny sowthistle
Rounded auricles are the distinctive trait of spiny sowthistle
seedlings have spatulate leaves with irregularly toothed margins
Seedlings of spiny sowthistle have spatulate leaves with irregularly toothed margins and a 'milky' appearance.
Authored by:
Bob Hartzler
Bob Hartzler
  • Retired Weed Scientist and Professor of Agronomy
Dr. Bob Hartzler is a former professor of agronomy and a former extension weed specialist with a Ph.D. in Crop Physiology from Iowa State University. He conducted research on weed biology and how it impacts the efficacy of weed management programs in corn and soybean. Dr. Hartzler also taught undergraduate classes in weed science and weed identification.
Meaghan Anderson
Meaghan Anderson
  • Field Agronomist in Central Iowa
Meaghan Anderson is a field agronomist serving nine counties in central Iowa and an extension specialist with Iowa State University Extension and Outreach. Areas of expertise include weed management, weed biology, cover crops, corn and soybean management, and integrated pest management.

Meaghan holds a bachelor's degree in agronomy and a master's degree in crop production and physiology (focus: weed science) from Iowa State University.
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