Common name
Rhodesian Sudan Grass
Wild Sorghum

Derivation
Sorghum Moench, Methodus 207 (1794), nom. cons.; the Indian name for this genus.

arundinaceum- from the Latin arundo (reed) and -acea (like). Culms tall, thereby resembling a reed.

Published in
Fl. Trop. Afr. 9: 116 (1917).

Common synonyms
Sorghum verticilliflorum (Steud.) Stapf
Sorghum bicolor (L.) Moench subsp. arundinacuem (Desv.) de Wet & Harlan

Habit
Annual or perennial, loosely tufted, short-lived. Young shoots extravaginal. Culms erect, 30–400 cm tall, 2–15 mm diam., without nodal roots or with prop roots or with aerial roots from the nodes. Mid-culm internodes hollow, thin-walled. Mid-culm nodes glabrous or pubescent. Lateral branches simple. Leaves cauline. Leaf-sheaths narrower than blade at the collar, smooth, glabrous on surface. Ligule a fringed membrane, 2–3 mm long, entire, truncate. Collar glabrous. Leaf-blades 5–85 cm long, 5–70 mm wide. Leaf-blade surface smooth. Leaf-blade margins scabrous, glabrous. Leaf-blade apex acute.

Inflorescence
Panicle open, linear or lanceolate or ovate, 10–60 cm long. Primary panicle branches not whorled, moderately divided, 30 cm long. Panicle branches flexuous, scaberulous, pubescent in axils. Rames 0.8–2 cm long, bearing 2–7 fertile spikelets on each. Rhachis fragile at the nodes, ciliate on margins. Rhachis hairs 0.5–1.5 mm long. Rame internodes filiform, 2–5 mm long. Rame internode tip transverse, cupiliform.

Spikelets
Spikelets appressed, in pairs, one sessile and fertile and the other (companion) spikelet pedicelled. Pedicels filiform, flattened, 50% of length of fertile spikelet, ciliate. Companion spikelets represented by single glumes or developed, male or sterile, comprising 2 subequal glumes without lemmas or male, linear to lanceolate, dorsally compressed, 3–8 mm long, shorter than fertile, separately deciduous. Companion spikelet glumes chartaceous, smooth, glabrous, acute, muticous. Companion spikelet lemmas enclosed by glumes. Fertile spikelets 2-flowered, comprising 1 fertile floret, lower floret sterile, upper fertile, without rhachilla extension, lanceolate to ovate, dorsally compressed, acute, 4–9 mm long, falling entire, deciduous with accessory branch structures. Spikelet callus base obtuse.

Glumes
Glumes dissimilar, with lower wider than upper, firmer than fertile lemma, shiny. Lower glume ovate, 100% of length of spikelet, coriaceous, much thinner above, keel-less except near apex, 9–13-nerved. Lower glume lateral nerves transversely connected at apex. Lower glume surface pubescent. Lower glume hairs white or yellow. Lower glume apex acute. Upper glume ovate, coriaceous, much thinner above, 7–8-nerved. Upper glume surface pubescent. Upper glume apex acute.

Florets
Basal sterile floret 1, without significant palea. Lemma of lower sterile floret lanceolate, 6 mm long, 80% of length of spikelet, hyaline, 2-nerved, ciliate on margins, acute. Fertile lemma ovate, dorsally compressed, 1–5 mm long, hyaline, 1-nerved. Lemma margins ciliate. Lemma apex dentate, 2-fid, muticous or 1-awned. Median (principal) awn from a sinus, geniculate, 0–30 mm long overall, with a twisted column. Column glabrous. Palea absent or minute. Lodicules 2, oblong, fleshy, ciliate, hairy across the apex. Anthers 3, 2–4 mm long. Stigmas 2, laterally exserted. Ovary glabrous. Grain with adherent pericarp, oblong, dorsally compressed, 2–3.5 mm long, glabrous. Embryo 60% of length of grain. Hilum punctiform. Endosperm farinose. Disseminule comprising a rhachis internode.

Continental Distribution:
Africa, Temperate Asia, Tropical Asia, Australasia, Pacific, North America, South America.

Australian Distribution:
Queensland, New South Wales.

Queensland: Cook, Burke, North Kennedy, South Kennedy, Port Curtis, Leichhardt, Burnett, Wide Bay, Darling Downs, Moreton. New South Wales: North Coast, Central Coast, South Coast, Northern Tablelands, Central Tablelands, North-Western Slopes, Central-Western Slopes, South-Western Slopes, North-Western Plains, South-Western Plains.

Classification. (GPWG 2001):
Panicoideae: Andropogoneae

Notes
Introduced. Widespread weed in the coastal areas of Qld and northern N.S.W. Flowers Mar.–May.