Flora of New Zealand Series

mugwort

Aromatic, rhizomatous, herbaceous perennial, dying back to rootstock each year. Stems erect, sparsely to moderately tomentose, becoming glabrous below, ribbed, up to 2-(3) m tall, usually not branched except above to form infl. Lvs scattered along stems, densely tomentose and sparsely glandular on lower surface, usually glabrescent on upper surface but sometimes sparsely hairy. Lower cauline lvs shortly petiolate, (1)-2-3-pinnatisect, up to 18 × 18 cm; ultimate segments subulate, or triangular to lanceolate, acute to apiculate, 5-70 × 3-10 mm (shortest segments in basal lvs), with evident central vein and faint lateral veins. Infl. paniculate; infl. lvs becoming apetiolate and 1-pinnatisect or not lobed, finally reduced to < 1 cm long. Outer involucral bracts herbaceous, sparsely to moderately hairy; inner bracts moderately hairy, with broad membranous margins and apex. Capitula 2-5 mm diam.; receptacle glabrous; florets (12)-15-25, yellow or reddish brown, with scattered glandular hairs. Achenes 1-1.5 mm long, brown, obovoid, slightly flattened, ± smooth; pappus 0 or a small scarious ring.

N.: from Gisborne, Bay of Plenty and Taupo northwards, local; S.: Blenheim, Timaru.

S.W. China 1926

Waste places.

FL (Dec)-Apr-Jul.

N.Z. material is somewhat variable in the extent of lf dissection and also in the presence of hairs on the upper surface of the lf; in most material the lvs are glabrous on the upper surface and 2-3-pinnatisect. N.Z. plants have previously been referred to the closely related A. vulgaris L.; however, a chromosome count of 2 n = 50 (M. Dawson, pers. comm.) for plants from both Okere Falls (near Rotorua) and Opotiki clearly identifies A. verlotiorum. It remains unclear whether A. vulgaris, with 2 n = 16, is also present in N.Z. A. vulgaris has shorter rhizomes, is less strongly scented, and the smaller lf veins are less distinct.