Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
49. Asteraceae, the Aster Family
17. Sonchus L. -- Sow thistle
1. Sonchus arvensis L. -- Field sow thistle
Stout, erect, milky-juiced perennial (3)5-15 dm tall, spreading by deep creeping
roots; stems glabrous or with spreading gland-tipped hairs above. Leaves
cauline, alternate, often larger and more crowded toward the base, lanceolate
to oblong or oblanceolate, pinnately lobed to pinnatifid or unlobed, 10-30 cm
long, 2-10 cm wide, acute to broadly rounded at the tip, prickly-margined, auriculate-clasping.
Inflorescence containing several to many heads, open, corymbiform, the
branches and involucres sometimes with spreading gland-tipped hairs; heads
ligulate, yellow, many-flowered, 2-3.5 cm across; involucres campanulate,
10-22 mm high, sometimes thinly tomentose at the base, the bracts linear, imbricate,
the outer ones much shorter than the inner; receptacle naked. Achenes
reddish-brown, flattened, 2-3.5 mm long; pappus of numerous white capillary
bristles, strongly accrescent. Late Jun--Aug. Wet meadows, shores, stream banks
and other wet places; also fields, woods and roadsides; very common in the n,
less so in the s; (A cosmopolitan noxious weed originating in Europe). S.
The great majority of plants in this region are subsp. uliginosus
(Bieb.) Nyman (S. arvensis var. glabrescens Guenth.), characterized
by glabrous stems and involucres. The subsp. arvensis is of limited
occurrence, often appearing restricted to municipal areas. It differs from
subsp. uliginosus in having spreading gland-tipped hairs on the upper
portion of the stem, the inflorescence branches and the involucres.
Previous Section -- Solidago riddellii Frank --
Return to Family -- Asteraceae - The
Next Section -- Vernonia fasciculata Michx.