Common name
Giant Reed
Reedgrass

Derivation
Arundinella Raddi, Agrost. Bras. 36 (1823); diminutive of the Latin arundo (a reed), alluding to the thin reedy habit.

setosa- from the Latin seta (bristle) and -osa (abundance). Each raceme subtended by a stout bristle.

Published in
Gram. Pan. 63 (1826).

Habit
Perennial, tufted. Rootstock evident. Rhizomes short. Basal leaf sheaths glabrous or woolly. Culms 50–120 cm tall, 2–5-noded. Mid-culm internodes glabrous or pubescent, with tubercle-based hairs. Mid-culm nodes glabrous. Lateral branches simple or sparsely branched. Leaf-sheaths glabrous on surface or pilose. Ligule a fringed membrane. Leaf-blades straight, flat, 10–40 cm long, 2–5 mm wide. Leaf-blade surface glabrous or puberulous to hirsute, with tubercle-based hairs. Leaf-blade margins glabrous or ciliate. Leaf-blade apex attenuate.

Inflorescence
Inflorescence compound, a panicle, bearing juvenile spikelets at emergence, exserted. Panicle open, oblong or ovate, nodding, 5–30 cm long, 3–6 cm wide, contracted about primary branches. Primary panicle branches 1–15 cm long. Panicle axis smooth or scabrous.

Spikelets
Spikelets solitary or in pairs, one sessile and fertile and the other (companion) spikelet pedicelled. Pedicels 3 mm long, scabrous, bearing a few hairs, hairy at tip. Fertile spikelets 2-flowered, comprising 1 fertile floret, without rhachilla extension, lanceolate, laterally compressed, 5–7 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Floret callus pubescent, obtuse.

Glumes
Glumes persistent, dissimilar, thinner than fertile lemma, gaping. Lower glume elliptic, 3–5 mm long, 60–70% length of upper glume, membranous, 1-keeled, 3–5-nerved. Lower glume surface scabrous, rough on nerves. Lower glume apex acuminate, mucronate or awned. Upper glume elliptic, 5.5–7 mm long, 20% of length of adjacent fertile lemma, membranous, 1-keeled, 5-nerved. Upper glume surface scabrous, rough on nerves. Upper glume apex acuminate or caudate, muticous or mucronate.

Florets
Basal sterile floret 1, with palea, persisting on inflorescence. Lemma of lower sterile floret similar to upper glume, elliptic, 3–4.5 mm long, 100% of length of spikelet, membranous, 1-keeled, 3–5-nerved, obtuse or acute. Palea of lower sterile floret 3 mm long. Fertile lemma lanceolate, 2.5–3 mm long, coriaceous, dark brown, 3–5-nerved. Lemma lateral nerves obscure. Lemma surface asperulous. Lemma margins involute, interlocking with palea keels. Lemma apex dentate, 2-fid, 3-awned. Median (principal) awn from a sinus, geniculate, 5–9.5 mm long overall, with a twisted column. Column 3.5 mm long. Lateral lemma awns present, arising on apex of lobes, 1.4–3.5 mm long. Palea with auriculate flaps, coriaceous, 2-nerved. Palea surface asperulous. Lodicules 2, cuneate, fleshy. Anthers 3, 1.5 mm long. Stigmas 2. Grain with adherent pericarp, 2 mm long. Embryo 60% of length of grain. Hilum punctiform.

Continental Distribution:
Temperate Asia, Tropical Asia, Australasia.

Australian Distribution:
Northern Territory, Queensland.

Northern Territory: Darwin & Gulf, Barkly Tableland. Queensland: Burke, Cook, North Kennedy.

Classification. (GPWG 2001):
Panicoideae: Arundinelleae

Notes
From Indo–Malesia and SE Asia to tropical Qld and N.T. Tropical savanna woodlands. Flowers Jan.–Aug.

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