Citronella Grass

This species yields citronella oil.

Perennial from a stout rootstock. Culms tufted, robust, up to 2.5 m tall, 1–2 cm in diam. Leaf sheaths reddish purple at base, smooth, glabrous; leaf blades dark green or dark brown when dry, drooping for 1/3 of their length, 30–100 × 1–2 cm, glabrous, abaxial surface scabrid, adaxial surface smooth, base narrow, apex long acuminate; ligule 2–3 mm. Spathate panicle large, narrow, congested, interrupted, 60–90 cm; spatheoles reddish brown, 1.2–2.5 cm; racemes 1–1.5 cm; rachis internodes and pedicels ciliate on margins; pedicel of homogamous pair not swollen. Sessile spikelet oblong-lanceolate, 3–4.5 × 1–1.2 mm; lower glume flat or slightly concave, reddish brown or purplish upward, sharply 2-keeled, keels narrowly winged, obscurely 0–3-veined between keels; upper lemma linear, entire or slightly 2-lobed, mucronate or very shortly awned. Pedicelled spikelet 3.5–7 mm. Fl. and fr. Nov–Apr. 2n = 40.

Commonly cultivated. Fujian, Guangdong, Hainan, Taiwan, Yunnan [native to S India and Sri Lanka; introduced elsewhere as a crop plant].

Andropogon nardus Linnaeus, Sp. Pl. 2: 1046. 1753.

Andropogon nardus L. Sp. PI. 1046. 1753
Sorgum Nardus Kuntze, Rev. Gen. 792. 1891.
A tall aromatic perennial, with the elongate leaves crowded at the base of the stem, and a large decompound inflorescence. Stems 1-2 m. tall, much branched; leaf -sheaths terete, smooth and glabrous, glaucous; blades up to 1 m. long, 1.5-2 cm. wide, glabrous, glaucous below; inflorescence up to 8 dm. long, lax; spathes narrowly cymbiform, 1.5-2 cm. long; racemes 1-1.5 cm. long, of 4 or 5 internodes, equaling or extending somewhat beyond the apex of the spathes ; perfect sessile spikelet 4-5 mm. long, lanceolate, narrowed from the middle or above, the first scale narrowly winged on the keels, the intercarinal space flat and 2-4-nerved, the fourth scale 2-toothed at the apex, muticous or mucronate; pedicellate spikelet staminate, acute.
Type locality : India.
Distribution: Old World tropics, often cultivated in the American tropics, and escaping in Florida, Jamaica, Martinique, and Guadeloupe.

Perennials, Terrestrial, not aquatic, Basal sheaths fibrous, old leaves persistent at base of plant, Stems nodes swollen or brittle, Stems erect or ascending, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Plants aromatic or malodorous, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems with inflorescence 1-2 m tall, Stems with inflorescence 2-6 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaf tips flexuous, drooping, blades thin, lax, soft, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades 1-2 cm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blade with prominently raised or widened midvein, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence with 2 or more spikes, fascicles, glomerules, heads, or clusters per culm, Inflorescence lax, widely spreading, branches drooping, pendulous, Inflorescence a p anicle with narrowly racemose or spicate branches, Inflorescence with 2-10 branches, Flowers bisexual, Spikelets pedicellate, Spikelets sessile or subsessile, Spikelets dorsally compressed or terete, Inflorescence or spikelets partially hidden in leaf sheaths, subtended by spatheole, Spikelet less than 3 mm wide, Spikelets with 2 florets, Spikelets paired at rachis nodes, Spikelets in paired units, 1 sessile, 1 pedicellate, Spikelets bisexual, Spikelets disarticulating below the glumes, Spikelets falling with parts of disarticulating rachis or pedicel, Spikelets conspicuously hairy , Rachilla or pedicel hairy, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glumes keeled or winged, Glumes 1 nerved, Glumes 3 nerved, Glumes 4-7 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 1 nerved, Lemma 3 nerved, Lemma glabrous, Lemma apex dentate, 2 -fid, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn less than 1 cm long, Lemma awn from sinus of bifid apex, Lemma awn twisted, spirally coiled at base, like a corkscrew, Lemma awn once geniculate, bent once, Lemma margins thin, lying flat, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis.

Cymbopogon nardus, common name citronella grass, is a species of perennial aromatic plant from the family Poaceae, originating in tropical Asia. C. nardus cannot be eaten because of its unpalatable nature and is an invasive species that renders pastureland useless, since cattle will starve even in its abundance.

It is the source of an essential oil known as citronella oil, which is widely used for its natural insect-repelling properties. Essential oils are extracted from the aerial parts and applied topically or slowly burned (e.g. in a "citronella candle") as an insect repellent, particularly to deter haematophagous insects such as mosquitoes.