Flora of New Zealand Series

Johnson grass

Robust perennials to 2 m, strongly rhizomatous with far-creeping, woody rhizome c. 0.5-10 mm diam., rooting at nodes, internodes covered by scale-like bracts. Leaf-sheath chartaceous, ± keeled above with strong midrib, glabrous, light green or straw-coloured, often streaked reddish purple, sometimes completely suffused red-purple near base. Ligule 3.5-5 mm. Leaf-blade to 90 × 1-2-(5) cm, linear, ± glabrous, adaxially densely pubescent near ligule, abaxially pubescent from margin, midrib prominent, pale cream; margins minutely scabrid. Culm simple, erect, internodes glabrous, often with red-purple streaks. Panicle large, rather open, (15)-20-30 cm, lower branches very long, narrowly ascending, sometimes ± pendulous, naked below. Racemes several towards ends of slender branches; rachis and pedicels finely short-hairy. Pedicelled spikelets: 5-7 mm, greenish or dark reddish, narrow elliptic-lanceolate, acute; anthers c. 3 mm. Sessile spikelets: glumes 4-5 mm, elliptic-lanceolate, almost glabrous to densely hairy; lemmas < glumes, hyaline, sparsely hairy, lemma of upper floret usually awned, awn geniculate, twisted, 10-15 mm; stamens 3, anthers 2-3 mm; caryopsis c. 3 × 1.5 mm.

N.: recorded from Whangarei, Auckland City, South Auckland, Gisborne (Muriwai), Hawke's Bay (Napier, Hastings), Taranaki (Hawera), Wellington (Wanganui, Bulls, Feilding); S.: recorded from Nelson (Motueka, Nelson City), Marlborough (Oaro, south of Kaikoura), Canterbury (Leithfield, Kaiapoi). Crops (especially maize), cultivated ground, waste ground, footpaths, railway lines.

Naturalised from Mediterranan.

Aggressive and extremely difficult to eradicate because of the extensive, very strong rhizomes.