Stems terete, fistulose. Leaves: petioles 1-10 cm, glabrous, puberulent, or densely hairy (hairs often brownish, crinkled); blades 3-12(-25) × 2-4(-6) cm, lateral lobes 0-20, mostly gradually reduced proximally, terminal lobes elliptic, ovate, obovate, or oblong-truncate, larger than laterals, apices obtuse or acute. Peduncles 1-5(-15) mm. Phyllaries 3.5-6 mm, bases and midribs becoming ± spongy, abaxial faces glabrous, glabrate, or hairy (hairs appressed, shining). Florets: corollas mostly 4.5-6.5 mm; anthers dark green (drying purplish); styles and style-branches yellow. Cypselae 1.5-2.5 mm, bases hollow, lightly calloused; pappi 2.5-3.5 mm, slightly surpassing phyllaries. 2n = 16. Flowering spring-summer (year-round south). Waste places, lawns, etc.; 0-2400 m; introduced; Ala., Ark., D.C., Fla., Ga., Ky., La., Md., Miss., N.Y., N.C., Pa., S.C., Tenn., Tex., Va.; se Asia; introduced also in Mexico, Central America, South America, Europe, Africa, Pacific Islands, Australia. Youngia japonica is now considered a pantropical weed. Relatively few specimens in the flora match what Babcock and Stebbins called subsp. elstonii, with cauline leaves almost as large as the basal and with conspicuous, lobed bracts at the bases of the proximalmost branches of the capitulescence. In subsp. japonica, to which most of our specimens are referred, the cauline leaves are much reduced or lacking, as are the bracts of the capitulescence.
Polymorphic, subscapose annual 1-9 dm, scabrous or ±hairy toward the base; lvs mainly or all basal, mostly lyrate-pinnatifid, or subentire in small plants, up to ca 20 נ6 cm; heads small, numerous in a corymbiform or paniculiform infl; fls ca 10-20, the tube ca 1/4 as long as the ligule; invol 3.5-5 mm, glabrous, with 4 short outer and ca 8 longer inner bracts; achenes brownish, 1.5-2.5 mm; pappus 2.5-3.5 mm; 2n=16. Native to se. Asia, now a pantropical weed, and becoming common on the coastal plain in se. U.S., n. to Pa. (Crepis j.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.