Xanthium spinosum L.
Bathurst bur
Erect annual, 10-100 cm tall. Stems sparsely to densely hairy above, becoming glabrous below, usually much-branched from base or above. Lvs sessile or shortly petiolate, with 1-2 axillary spines; spines stout, (2)-3-(4)-fid, (0.5)-1-3 cm long; lamina with scattered hairs on upper surface and dense white to grey tomentum on veins and lower surface, mostly narrow-ovate, entire or pinnately 3-(5)-fid, obtuse to cuneate at base, 2-10 cm long; segments narrowly ovate-lanceolate, lanceolate, or triangular; uppermost lvs often smaller, narrower and entire. ♂ capitula in terminal infls, with numerous florets; ♀ capitula solitary or clustered, in axils. Fruiting involucre sparsely to moderately clothed in short hairs, less hairy at maturity, 10-13 × 5-7 mm; prickles hooked, glabrous, 2-3 mm long; beaks 1-2, indistinct, 0.5-1 mm long.
N.: local throughout; S.: Richmond (Nelson), Fairhall (Marlborough), Broomfield (N. Canterbury), Invercargill.
S. America 1867
Waste places, coastal sites, pasture, cultivated land, gardens.
FL Dec-Apr, FR Dec-Jul.
X. spinosum is fairly uniform in most characters and is easily distinguished from the very variable X. stumarium by the axillary spines and the short-beaked fruiting involucre (Fig. 25).
