Xanthium spinosum
Gerald D. Carr

Flora of Oregon

Plants 1–8+ dm.

Stems puberulent to hispidulous or tomentose, with 2–3-branched spines at the nodes.

Leaves blades narrowly lanceolate to elliptic, 2–15 × 1–4 cm, bases cuneate or attenuate, margins entire to toothed or lobed, tips acute or acuminate, surfaces abaxially densely strigose, adaxially glabrate to sparsely strigose.

Burs 1–1.5 cm, prickles slender; beaks 0–1.

2n=36.

Roadsides, disturbed areas, streambanks, fields. Flowering Jun–Oct. 0–1600 m. BW, Col, ECas, Est, Owy, Sisk, WV. CA, ID, NV, WA; nearly worldwide. Exotic.

The seeds and seedlings of this species are poisonous and may cause death of livestock. It is listed as a Class B Noxious weed in Oregon.

Flora of North America

as described under Xanthium spinosum

Plants 10-60(-120+) cm; nodal spines usually in pairs, simple or 2-3-partite, 15-30+ mm. Leaves: petioles 1-15(-25+) mm; blades ± ovate to lanceolate or lance-linear, 4-8(-12+) × 1-3(-5+) cm, often pinnately 3(-7+)-lobed, abaxial faces gray to white, densely strigose. Burs 10-12(-15+) mm. 2n = 36.Flowering Jul-Oct. Damp or seasonally wet, alkaline soils, waste places, margins of agriculture; 10-1000 m; N.B., Ont., Que., Sask.; Ala., Ariz., Calif., Colo., Conn., Del., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., Maine, Md., Mass., Mich., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.C., Tenn., Tex., Utah, Va., Wash., W.Va.; Mexico; Central America; South America; widely established in Old World.Some authors have contended that Xanthium spinosum originated in South America and is introduced and/or naturalized everywhere else that it is found.

Photo images

/imglib/_OFPFP/201704/DIG42327_1492399061_tn.jpg
/imglib/_OFPFP/201704/DIG42328_1492399017_tn.jpg
/imglib/_OFPFP/201704/DIG42332_1492399528_tn.jpg
/imglib/_OFPFP/201704/DIG42324_1492399520_tn.jpg
/imglib/_OFPFP/201704/DIG42325_1492399247_tn.jpg

Herbarium specimens

/imglib/OSU_OSC/OSC184/07OSC184445_1492397290_tn.jpg
https://www.pnwherbaria.org/images/thumbnail.php?Image=CIC034021.jpg
https://www.pnwherbaria.org/images/thumbnail.php?Image=CIC026682.jpg
https://www.pnwherbaria.org/images/thumbnail.php?Image=SOC02224.jpg
https://www.pnwherbaria.org/images/thumbnail.php?Image=SOC06388.jpg