Flora of New Zealand Series

giant hogweed

Erect biennial. Stems hispid, hollow, grooved, reddish purple blotched and spotted, particularly toward base, up to 350 cm high and 10 cm diam. Basal lvs moderately hispidulous below, sparsely above, pinnately 3-foliolate, petiolate; leaflets ovate to ovate-lanceolate, deeply ternately or pinnately lobed and irregularly double serrate, up to 50-(100) cm long; lobes usually acute to acuminate; stem lvs similar to basal, with petiole often reduced to sheathing part only; petioles reddish purple blotched and spotted. Umbels (20)-30-60 cm diam.; rays (20)-50-70-(100), the primary umbels > 50-rayed; bracts usually c. 12, linear, 10-15 mm long; bracteoles 8-12, linear, up to 15 mm long. Fls numerous, white; outer fls irregular and up to 15 mm diam. Fr. glabrous, ovate-elliptic, light brown, c. 10 mm long; vittae conspicuous, 0.5-1 mm wide at base.

N.: Dannevirke, Napier, Wellington City; S.: scattered localities in Marlborough, Canterbury, Otago and Southland.

S.W. Asia 1968

Established locally in waste places, gardens and particularly in palustral situations.

FL Dec-Feb.

Poisonous (Connor 1977).

Giant hogweed is easily distinguished in the field by its size and flattened seeds with conspicuous oil canals (Fig. 12), and further from H. sphondylium by the spotted and blotched stems and petioles. Giant hogweed is sometimes cultivated as an ornamental curiosity. Connor (1977) suggested that there are 2 giant heraclea naturalised in N.Z. but collections of naturalised plants are all referable to H. mantegazzianum.