Flora of New Zealand Series

purple cudweed

Annual or biennial, 10-60-(75) cm tall, usually branched only at base; stems 1-several, erect or ascending. Basal lvs usually present at flowering, sometimes dead but persistent, apetiolate, spathulate to elliptic-oblong, 20-110-(150) mm long. Lower cauline lvs apetiolate, densely white-tomentose on lower surface, usually glabrous on upper, sometimes sparsely hairy on upper when young, strongly discolorous, plane, oblong to spathulate or oblanceolate, usually obtuse, rarely acute, mucronate, usually flat, sometimes undulate, 20-90 × 4-18 mm; upper cauline lvs smaller, broader based, often ± oblong, sometimes folded. Capitula in dense terminal and axillary clusters; clusters usually forming a dense terminal spike and often scattered below, rarely infl. diffuse and much-branched. Involucral bracts oblong, acute to apiculate, 2.5-3.2 mm long; stereome usually green, rarely reddish purple toward apex; lamina pale brown, often darker toward base; gap and margins usually clear, rarely flushed reddish purple; outer bracts glabrous. Achenes minutely papillate, c. 0.6 mm long.

N.: throughout; S.: Nelson, Marlborough, Westland, Fiordland.

S. America 1896

Mostly forest margins and clearings, waste places, and lawns, also riverbeds, coastal sites, pasture, cultivated land, especially wet or stony sites from sea level to 1000 m.

FL Sep-Mar-(Aug).

G. coarctatum is by far the commonest of the spicate cudweeds naturalised in N.Z. It is usually easily distinguished by the distinctly discolorous lvs with a glabrous, shiny upper surface, and the dense spike, although it is very variable in habit and may be extremely depauperate in some habitats. Until Drury's treatment (1971, op. cit.) it had usually been known in N.Z. as G. purpureum, and since then usually as G. spicatum. G. americanum Miller is accepted as distinct although it is often difficult to distinguish from reduced plants of G. coarctatum. G. americanum can be distinguished by the bracts which are slightly reflexed at the apex and 3.5-4 mm long rather than usually erect and 2.5-3.2 mm long as in G. coarctatum. The lvs of G. coarctatum are usually quite glabrous on the upper surface; plants with hairy lvs may appear similar to G. purpureum but are easily distinguished by the much shorter bracts.