Sonchus arvensis L.
perennial sow-thistle (field sowthistle)
Asteraceae (Aster family)

Introduction to Vascular Plants


© Paul Handford     (Photo ID #68720)


E-Flora BC Static Map

Distribution of Sonchus arvensis
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Perennial sow-thistle is a common introduced weed species in southern British Columbia that originates in Europe. It is found along roadsides and in other disturbed sites. It can be identified by the yellow composite (daisy-like) flower heads with strap-shaped flowers, lack of basal leaves, and prickly-margined stem leaves. Plants exude milky juice when broken. .

Species Information

Perennial herb from a long, vertical and horizontal, rhizome-like, deep-seated root; stems erect, solitary, few-branched above, glabrous below, usually glandular-bristly above, hollow, exuding milky juice when broken, 0.4-2.0 m tall.
Basal leaves lacking; stem leaves alternate, prickly-margined, deeply lobed or pinnately cut, 6-40 cm long, 2-15 cm wide, with clasping leaf bases, upper leaves reduced.
Heads with strap-shaped flowers, several on glandular stalks in an open, flat- or round-topped inflorescence, relatively large, commonly 3-5 cm wide in flower; involucres 14-22 mm tall; involucral bracts lanceolate, tapering to a slender tip at the apex, glabrous, obscurely woolly-hairy or more or less copiously covered with coarse, spreading, gland-tipped hairs and often with tufts of woolly-hair as well, outer ones often becoming ridged-thickened in age; ray flowers yellow.
Achenes 2.5-3.5 mm long, ribbed, cross-wrinkled; pappus of white hairlike bristles.
Two varieties occur in BC:

1. Involucres and stalks of the heads with coarse, spreading, gland-tipped hairs................. var. arvensis

1. Involucres and stalks of the heads glabrous or obscurely woolly-hairy...................... var. glabrescens Guenth., Grab. & Wimm.

SourceThe Illustrated Flora of British Columbia


Ecological Framework for Sonchus arvensis

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres)
780 2 2101
Slope Gradient (%)
14 0 110

Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]

178 15 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
4 0 8
Modal Nutrient Regime
# of field plots
 species was recorded in:
Modal BEC Zone Class

All BEC Zones (# of stations/zone) species was recorded in

BG(9), CDF(1), CWH(1), ESSF(1), ICH(4), IDF(35), MS(1), PP(20), SBS(4)

Habitat and Range

Mesic to dry ditches, roadsides, disturbed areas and gardens in the lowland, steppe and montane zones; common in S BC; introduced from Europe.

SourceThe Illustrated Flora of British Columbia


Synonyms and Alternate Names:
Sonchus arvensis var. glabrescens Guenth., Grab. & Wimm.
Sonchus uliginosus M. Bieb.