Iris pseudacorus L.
Yellow Flag
Clumps very leafy, many-flowered, to 1 m high, dark green, ± glaucous, purple at base. Rhizome c. 3 cm diam., reddish-brown. Leaves c. = stems, 2-3 cm wide, cross-veinlets apparent when leaf is held up to light, midrib distinct. Stems terete, with several long leaves. Inflorescence usually branched, central axis and each branch terminated by 2-5-flowered clusters. Flowers to 12 cm diam., yellowish, varying from golden-orange to very pale cream, without scent; pedicels long, stout, > ovary; tube funnel-shaped, ± ½ length of ovary; outer segments 7 cm long, oval-oblong, limb c. 4 cm wide, very drooping, abruptly narrowed to dark brown-veined claw; inner segments c. 3 cm long, shorter and narrower but more erect than style-branches. Style-branches oblong, bifid crest fimbriate. Capsule c. 5 × 2 cm, oblong-elliptic, beaked; seeds brown, ± trigonous.
N. Taranaki - Mt Egmont; Wellington - Manawatu, Masterton, Hutt Valley. S. Marlborough-Blenheim; Canterbury; Southland - Riverton. Along rivers, streams and water races, and in swampy ground.
(Europe, Asia, N. Africa)
First record: Kirk 1878a: 368.
First collection: Waiwhetu Stream, Hutt Valley, V. D. Zotov, 2.12.1938 (CHR 21567, 21568). The large leafy clumps, and tall stems with conspicuous yellow flowers readily distinguish this water-loving iris.
FL. 11-12.
Still occasionally planted as an ornamental about garden ponds, this escape is a nuisance in some localities in drains, water races and slow-moving streams, impeding water flow. It is a prominent feature along the lower Avon River, Christchurch, and noticeable in some water races.
Spread is by seed, and vegetatively by portions of clumps eroded and dispersed by floodwaters.
