Origin:
Introduced from the Mediterranean region, and now a widespread problem weed in northern California, where it can be found in turf, landscape, roadsides and vacant lots.
Biology:
Grows as either an annual, a biennial, or even a short-lived perennial weed, with reproduction from seeds.
Identification:
Mature plants grow up to 3 feet tall, with hollow but stout stems leading to the numerous flower heads. At each stem node the stem seems to angle slightly, and stems and leaves are covered with stiff, barbed hairs or spines. Lower leaves are larger than the upper leaves, and they are on a short stalk at their base, while the upper leaves are clasping around the stem. Lower leaves have rounded tips and wavy margins, while upper leaves are pointed at the tips but have smooth margins. Many of the spines on the leaves arise from prominent blister-like swellings over the leaf surface. Flowers are yellow and daisy-like and the tips of the petals are notched or toothed. The flower heads are in small groups with each flower head on a short stalk. Around the base of each flower head there are spiny bracts covered with bristles as well.
Characteristicts Important to Control:
This plant may be physically removed, although the spiny nature makes this somewhat difficult.
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