Field Sow Thistle (Sonchus arvensis)
Like a punk dandelion. The leaves are shaped like dandelion leaves, but ringed with spines. The flower heads are like a slightly inebriated dandelion head, with its rays a bit ragged and unkempt. This plant grew in a corner of a front yard in Beechview, where it was blooming in early August.
Gray describes the genus and the species:
SÓNCHUS [Tourn.] L. SOW THISTLE. Heads many-flowered, becoming tumid at base. Involucre more or less imbricated. Achenes obcompressed, ribbed or striate, not beaked; pappus copious, of very white exceedingly soft and fine bristles mainly falling together. — Leafy-stemmed coarse weeds, chiefly smooth and glaucous, with corymbed or umbellate heads of yellow flowers produced in summer and autumn. (The ancient Greek name. )
Perennial, with creeping rootstocks; flowers bright yellow, in large heads.
S. arvénsis L. (FIELD S.) Leaves runcinate-pinnatifld, spiny-toothed, clasping by a heart-shaped base; peduncles and involucre bristly; achenes transversely wrinkled on the ribs. — Roadsides, fields, and gravelly shores, Nfd. and N. S. to N J., w. to the Rocky Mts., commonest northw. (Nat. from Eu.)