Annuals or biennials, 10-140(-200) cm. Stem bases soft to hard, herbaceous, often hollow. Leaves: blades of mid cauline spatulate or oblong to obovate or lanceolate, 6-35 × 1-15 cm, bases auriculate, auricles deltate to lanceolate, ± straight, acute, margins usually pinnately (often runcinately) lobed, lobes ± deltate to lanceolate, not constricted at bases, terminals usually larger than laterals, entire or dentate. Peduncles usually glabrous, sometimes stipi-tate-glandular. Involucres 9-13+ mm. Phyllaries usually glabrous, sometimes tomentose and/or stipitate-glandular. Corollas: ligules ± equaling tubes. Cypselae dark brown, mostly oblanceoloid, 2.5-3.5+ mm, ribs 2-4 on each face, faces transversely rugulose or tuberculate across and between ribs; pappi 5-8 mm. 2n = 32, 36. Flowering (Apr-)Jul-Oct (year-round in south). Disturbed sites, gardens, roadsides, along streams; 0-2000 m; introduced; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kansas, Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; introduced also in Mexico, West Indies, Bahamas, Central America, South America, Africa, Asia, Pacific Islands (New Zealand), Australia.
From Flora of Indiana (1940) by Charles C. Deam
There are reports of this species being found throughout the state. In my early botanical work I did not collect what I considered common garden weeds, and in most instances this accounts for the comparative paucity of specimens of these common plants. This species is a weed and prefers rich soil. It is found mostly in gardens, truck gardens, waste places, and fallow fields and along railroads and roadsides.
FNA 2006, Wiggins 1964, Kearney and Peebles 1969
Duration: Annual Nativity: Non-Native Lifeform: Forb/Herb General: Annual introduced herb; native to Europe; 10 cm-2 m tall; from a short taproot; glabrous except for an occasional spreading gland-tipped hair on the involucres and peduncles; milky sap. Leaves: Alternate; pinnatifid to occasionally merely toothed; soft; the margins only weakly or scarcely prickly; 6-30 cm long and 1-15 cm wide; all but the lowermost prominently auriculate; leaves progressively less divided upwards. Flowers: Heads several in a corymbiform inflorescence; relatively small; 1.5-2.5 cm wide in flower; involucre 9-13 mm high in fruit; yellow rays; 120-150 flowers per plant. Fruits: Cypselae 2.5-3.5 mm long; transversely rugulose and 3-5 ribbed on each face. Ecology: Found in disturbed areas; 600-8,000 ft (185-2440 m); flowers March-October. Distribution: Introduced to every continent in the world; occurs throughout N. America and in every state in the US; south through MEX to S. America. Notes: An annual with milky sap, becoming robust in the right conditions; erect with clasping leaves with wavy, dentate margins, each tooth with a sharp spine. Two other species of Sonchus in the Intermountain West. S. arvensis is also native to Europe and widely introduced in North America; prefers fairly moist to wet soil. It is a perennial with deep-seated creeping roots and relatively large flowers. S. asper is an annual introduced species occurring in meadows, along streambanks and obviously disturbed habitats. It differs from S. oleraceus by having clasping leaf-bases which are recurved and not relatively straight as in oleraceus and mature several-nerved achenes that are not rugulose (mature achenes are transversly rugulose as well as several-nerved in S. oleraceus). Ethnobotany: Young leaves are used in salads or cooked in curry and rice dishes. Salves are used to treat hemorrhoids and ulcers. Tea is used to treat anxiety and asthma. The milky juice is often used as eyewash. Etymology: Sonchus is the Greek name for sowthistle, while oleraceus means resembling garden herbs or vegetables used in cooking. Synonyms: None Editor: SBuckley 2010, FSCoburn 2015
Annual 1-20 dm from a short taproot, glabrous except sometimes for a few spreading gland-tipped hairs on the invols and peduncles; lvs pinnatifid to occasionally merely toothed, soft, the margins only weakly or scarcely prickly, 6-30 נ1-15 cm, all but the lowermost ones prominently auriculate, the auricles well rounded but eventually sharply acute; lvs progressively less divided upward and ±reduced; heads several in a corymbiform infl, relatively small, 1.5-2.5 cm wide in fl; invol 9-13 mm in fr; fls 80-250 per head; cor-tube about equaling the ligule; achenes 2.5-3.5 mm, transversely rugulose and evidently to rather obscurely 3-5-ribbed on each face; 2n=32, 36. A cosmopolitan weed, native to Europe. July-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.