Common name
Thatch Grass

Derivation
Hyparrhenia Andersson ex E.Fourn., Mex. Pl. 2: 51 (1886); from the Greek hypo (under) and arren (masculine), alluding to the male spikelets at the base of the racemes.

rufa- Latin for reddish. Inflorescence purple to red.

Published in
Fl. Trop. Africa 9: 304 (191).

Habit
Perennial, tufted. Rhizomes short. Basal leaf sheaths glabrous. Young shoots intravaginal. Culms erect, 30–300 cm tall, 2–6 mm diam. Mid-culm internodes solid. Lateral branches fastigiate. Leaves cauline. Leaf-sheaths wider than blade at the collar. Ligule an eciliate membrane, 2–3 mm long. Leaf-blades 10–60 cm long, 2–8 mm wide. Leaf-blade margins smooth. Leaf-blade apex attenuate, filiform.

Inflorescence
Inflorescence terminal and axillary, subtended by a spatheole, exserted. Spatheole linear to lanceolate, 2.5–5 cm long, membranous. Peduncle 3–8 cm long, glabrous or pilose above. Rames paired, erect or deflexed, unilateral, 1.5–4 cm long, bearing 4–7 fertile spikelets on each. Central inflorescence axis 5–80 cm long. Rhachis fragile at the nodes, ciliate on margins. Rhachis hairs red. Rame internodes linear. Rame internode tip oblique, flat. Rame-bases filiform, 2–3.5, glabrous, unequal.

Spikelets
Spikelets appressed, in pairs, one sessile and fertile and the other (companion) spikelet pedicelled. Pedicels linear, flattened, ciliate, tip oblique. Basal sterile spikelets well-developed, 2 in lower raceme, 0–2 in upper racemes. Basal sterile spikelets equalling fertile. Basal sterile spikelet glumes smooth on margins. Basal sterile spikelet lower glume muticous. Companion spikelets developed, containing empty lemmas or male, lanceolate or elliptic, dorsally compressed, 3.5–5 mm long, as long as fertile, separately deciduous. Companion spikelet glumes chartaceous, pilose, with white hairs (rarely) or red hairs, acute, muticous. Companion spikelet lemmas 2, enclosed by glumes. Fertile spikelets 2-flowered, comprising 1 fertile floret, lower floret sterile, upper fertile, without rhachilla extension, lanceolate or elliptic, dorsally compressed, 3.5–5.5 mm long, falling entire, deciduous with accessory branch structures. Spikelet callus oblong to cuneate, 0.2–0.8 mm long, pubescent, base obtuse, attached obliquely. Spikelet callus hairs white or yellow.

Glumes
Glumes dissimilar, with lower wider than upper, firmer than fertile lemma, shiny. Lower glume lanceolate, 100% of length of spikelet, chartaceous or coriaceous, 5–11-nerved. Lower glume surface pubescent or pilose. Lower glume hairs red. Lower glume apex entire or dentate, 2-fid, truncate. Upper glume linear, 110% of length of adjacent fertile lemma, chartaceous or coriaceous, 3-nerved. Upper glume apex dentate, 2-fid, acute, mucronate.

Florets
Basal sterile floret 1, without significant palea. Lemma of lower sterile floret lanceolate, 100% of length of spikelet, hyaline, 2-nerved, entire. Fertile lemma linear, 3–4 mm long, membranous, 1-nerved. Lemma apex dentate, 2-fid, 1-awned. Median (principal) awn from a sinus, geniculate, 20–30 mm long overall, with a twisted column. Column pubescent, with 0.2–0.4 mm long rufous hairs. Palea absent or minute. Lodicules 2, cuneate, fleshy. Anthers 3, 1–2 mm long. Stigmas 2.

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

Australian Distribution:
Northern Territory, Queensland.

Northern Territory: Darwin & Gulf. Queensland: Cook, North Kennedy, South Kennedy, Port Curtis, Leichhardt, Burnett, Wide Bay, Moreton.

Classification. (GPWG 2001):
Panicoideae: Andropogoneae

Notes
There are two subspecies.

Hyparrhenia rufa subsp. rufa
Introduced from Africa. Flowers Feb.–Aug.

Hyparrhenia rufa subsp. altissima (Stapf) B.K.Simon
Introduced from Africa. Flowers Mar–June.