E-Flora BC: Electronic Atlas of the Flora of British Columbia

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

Introduction to Vascular Plants

© Paul Handford  Email the photographer   (Photo ID #68720)

E-Flora BC Static Map
Distribution of Sonchus arvensis
Click here to view the full interactive map and legend
Details about map content are available here
New! Click on the map dots to view record details.

Introduction

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

Click on the image below to view an expanded illustration for this species.



General:
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.
Leaves:
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.
Flowers:
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.
Fruits:
Achenes 2.5-3.5 mm long, ribbed, cross-wrinkled; pappus of white hairlike bristles.
Notes:
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.

Source: The Illustrated Flora of British Columbia

Habitat / Range

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

Source: The Illustrated Flora of British Columbia

Ecology

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

Minimum

Average

Maximum

Elevation (metres) 2 780 2101
Slope Gradient (%) 0 14 110
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
15 178 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 4 8
Modal Nutrient Regime
Class
D
Number of field plots
 species was recorded in:
77
Modal BEC Zone Class
IDF
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)

Climate

The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Sonchus arvensis var. glabrescens Guenth., Grab. & Wimm.
Sonchus uliginosus M. Bieb.

Taxonomic and Nomenclatural Links

Additional Photo Sources

Related Databases

General References