Silybum marianum (L.) Gaertn.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Glabrous or slightly tomentose, 6–15 dm; lvs pinnately lobed, less so upwards, to 4 dm and nearly half as wide, petiolate below, becoming sessile and strongly auriculate-clasping above, spiny-margined, ± marked with white along the main veins; coarse, spreading tips of the invol bracts basally expanded; disk 3–6 cm wide; achenes 6–7 mm; 2n=34. A weed in waste places and about ballast-dumps; native of the Mediterranean region, rarely seen here and there in our range. May–July. (Mariana m.)