Common Name: sowthistle, spiny
Species: Sonchus asper (L.) Hill
Bayer Code: SONAS

Spiny sowthistle is a summer annual weed with a basal rosette and an upright flowering stem. The leaves are deeply notched and wavy. Spiny sowthistle has yellow flowers that appear in late spring, and the leaves and stems emit a milky-white latex when crushed. The weed is found in open habitats that include waste areas, turf, and roadsides.
spiny sowthistle seedheads
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sowthistle leaf arrangement
sowthistle leaves, stem
sowthistle
sowthistle leaves, stem
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CharacteristicTypeDescription
Growth Season summer annual weed 
Growth Habit upright OR rosetteyoung plant is a basal rosette, older plant is upright
Leaflet Number one 
Leaf Margin lobed 
Leaf Hairs nonegenerally, leaves are hairless but have sharp prickles on leaf margins
Leaf/Leaflet Shape oval/egg-shaped/ellipticalnote the clasping lobes at the base of leaves
Leaf Width 1/2 - 1 inch 
Leaf Venation pinnate 
Leaf Arrangement alternate 
Root Type taproot 
Flower Color yellow