Common Sow Thistle

Scientific Name: Sonchus oleraceus
Family Name: Asteraceae

Flower: ½ - 1 in. (1.2 – 2 cm.) wide, yellow center with yellow rays coming off the center. Several flowers grow at the end of one stem.

Leaf: 2.3 - 12 in. (6 – 30 cm.) long, .4 - 6 in. (1 – 15 cm.) wide, alternate waxy, green leaves. The leaves are lobed, with a triangular lobe at the top, and 3 pairs of lower lobes that are smaller closer to the ground. The leaves are also toothed, with sharp prickly teeth.
Plant: 1 – 8 ft. (30 - 240 cm.) tall with a smooth stem. When the stem or leaves are broken, they exude a milky sap.

Identifying Characteristics: Common Sow Thistle is very difficult to identify from other thistles, particularly the Spiny Sow Thistle. One helpful difference is the relative thinness of Common Sow Thistles leaves from the more ovate leaves of the other thistles. Another identifying characteristic is the height of the plant, which is generally taller than other thistles.

Location: We found Common Sow Thistle growing at a rest area of Rt. 128 near Dedham, Massachusetts.

History and Comments: Common Sow Thistle is native to Europe. It now grows all over the United States and is considered a weed. It thrives in disturbed places, particularly along road sides. Common Sow Thistle was also introduced to New Zealand from Europe, and there they eat it as a garden vegetable.

    Unless otherwise specified, all text, photographs, and drawings are Copyright (c) by Shu-Yee Chen and Deborah Hamer 2003. No part of this page may be reproduced without prior written consent of the authors.