Field Guide to Noxious and Other Selected Weeds of British Columbia

Perennial Sow-thistle (Sonchus arvensis) and Annual Sowthistle (Sonchus oleraceus)

Photo courtesy Dean Swan, Washington State University (retired)

Provincial Noxious Weeds
Perennial sow-thistle is a creeping rooted perennial growing 0.4 to 1.5 metres tall; stems branch near the top; leaves with weak marginal prickles clasp the stem; plants contain a bitter milky juice; upper stalks and flower bracts usually covered in gland-tipped hairs; yellow flowers up to 3.8 cm broad
often confused with annual sow-thistle (Sonchus oleraceus) (Provincial Noxious) which is taprooted and has much smaller flowers (less than 2.5 cm across) or spiny annual sow thistle (Sonchus asper) which has sharp, spiny leaves and smaller flowers.

	Perennial sow-thistle with milky latex and clasping stem Photo courtesy Dean Swan, Washington State University (retired)
	Spiny annual sow-thistle
	Annual sow-thistle Photo courtesy Dean Swan, Washington State University (retired)

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