Flora of New Zealand Series

giant reed

Large robust perennial clumps to 5 m, with very wide leaves, and stout, woody, thick and knotty rhizomes up to 3 cm diam. Leaf-sheath rounded, coriaceous, smooth and glabrous, long hairy at apex. Ligule 1-2 mm, truncate, short-ciliate, collar brownish with some long soft tangled hairs. Leaf-blade 30-60 × 2.5-5 cm, cordate at base, scabrid on margins and abaxially on the much-narrowed, long-tapered tip, otherwise smooth. Culm erect, internodes smooth. Panicle 30-50 cm, plume-like, very densely branched; branches obliquely ascending, scabrid from fine teeth. Spikelets 10-12 mm, 2-4-flowered, purplish later becoming brownish. Glumes ± equal, the lower including lemmas, 3-nerved, glabrous, lanceolate, acute to acuminate. Lemma 7-9 mm, 5-7-nerved, densely, soft long (c. 5 mm) hairy from below, lanceolate, tapered, lateral lobes 2, very short, awn-tipped, sinus with awn 2-3 mm, straight. Palea < lemma, apex ciliate, keels shortly densely ciliate. Callus sharp, small, glabrous, sparse hair tufts c. 1 mm. Rachilla and prolongation c. 2 mm, glabrous. Lodicules 2, c. 0.5 mm, cuneate, 3-nerved, glabrous, irregularly toothed. Anthers 2.5-3.5 mm. Gynoecium: ovary 0.5 mm, stigma-styles to 2 mm. Caryopsis not seen. Fig. 15.

N.; S.: occasional garden escape. Roadsides and sandy waste land.

Naturalised from Eurasia.

In N.Z. many megagametophytes fail to reach maturity [Philipson, M. N. and Connor, H. E. Bot. Gaz. 145: 78-82 (1984)]; seeds will rarely be found.

A. donax is grown as an ornamental; a variegated form is also grown and may escape into the wild.

Fig. 15 Arundo donax S, spikelet, × 7; G 1, G 2, glumes, × 7; L, lemma ventral view and dorsal view flattened to show nervation, × 7; P, palea ventral view with callus and hairs, dorsal view, × 7; Lo, lodicules, × 24; O, ovary, styles and stigmas, × 14; St, anthers, × 14. © All rights reserved. [Image: 4X7I]