Wildflowers of Toronto's High Park​​

Sow-thistles

Family: Composite/Aster
Genus: ​Sonchus
​Introduced

Habitat: Roadsides and waste places
Blooms: Summer and fall

Flower heads: Yellow ray florets
Leaves: deeply lobed with prickly edges
Seed heads: hairy. Seeds dispersed by wind. 

Sow-thistle, field
​S. arvensis

​Perennial

Height: up to 2 m
Flower head: 3-5 cm

Hairy bracts and stalks. 

Leaves: heart-shaped at the base where they clasp the stem.

Plant also spreads by creeping underground stems.


 

Sow-thistle, common
​S. oleraceus

Annual

​Height: up to 2.5 m 
Flower head: up to 2.5 cms

Smooth bracts and stems.  

Leaves with pointed lobes at the base where they clasp the stem. 

Sow-thistle, spiny-leaved
​S. asper

Annual

​Height: up to 1.5 m 
Flower head: up to 2.5 cms

Leaves with wavy margines that curve into ear-like claspng lobes at the base.