| Mary E. Barkworth |
Plants usually perennial; cespitose.
Culms 15-300 cm. Leaves aromatic, smelling of lemon oil or citronella;
sheaths open, not strongly keeled except near the summit; ligules
membranous; blades usually glabrous or mostly so, with long filiform
apices. Inflorescences terminal and axillary, false panicles; peduncles
often enclosed in the subtending leaf sheaths at maturity, with 2 rames; rames
with 4-7 heterogamous spikelet pairs, axes slender, without a median groove,
lower rame of each pair with 1 homogamous spikelet pair at the base, its pedicel
swollen and more or less fused to the adjacent internodes, upper rames with
short, sterile, flattened bases that are usually deflexed at maturity, without
homogamous spikelet units. Heterogamous spikelet units: sessile spikelets
dorsally compressed, with 2 florets; lower glumes chartaceous, concave
or flat, 2-keeled, with or without intercostal veins, often streaked with oil
glands; upper florets with a short, glabrous awn (rarely unawned); pedicels
linear, free from the rame axes; pedicellate spikelets well-developed.
x = 10. Name from the Greek kymbe, boat, and pogon, beard,
referring to the boat-shaped leaf sheaths subtending the usually hairy rames
(Clifford 1996).
Cymbopogon comprises 55 species, and is native to the tropics and subtropics
of the Eastern Hemisphere. It is cultivated in southern Florida and California,
sometimes persisting for a considerable period. Plants grown outdoors in the
Flora region generally remain vegetative, but can usually be identified
to genus by their lemony aroma. Heteropogon
melanocarpus also smells lemony when fresh but, unlike the species
of Cymbopogon that have been grown in the United States, it has a row
of glandular depressions over the well-developed keels of the lower leaf sheaths.
Identification of any grass to species in the absence of reproductive
parts is difficult. The key for use on vegetative plants of the three species
of Cymbopogon reported from the Flora region should be used only
as a last resort.
Cymbopogon citratus
and C. nardus are cultivated commercially
for their oils (lemon oil and citronella oil, respectively), which are used
in cooking and perfume, and as an insect repellent; C. citratus and C.
jwarancusa are also grown for their medicinal value.
REPRODUCTIVE KEY
1 |
Pedicels
pilose on the margins, glabrous dorsally ..... 2. C.
nardus |
Pedicels pilose on the margins
and the dorsal surface (2) |
|
Lower glumes of the sessile
spikelets shallowly concave distally; the keels not winged; ligules 2-6
mm long; blades whitish ..... 1. C.
jwarancusa |
|
Lower glumes of the sessile spikelets
flat above, the keels narrowly winged; ligules 0.5-2 mm long; blades green
..... 3. C. citratus |
VEGETATIVE KEY
1 |
Ligules
0.5-2 mm long, truncate, the nodes not swollen .ss.... 3. C. citratus |
Ligules 2-6 mm long, truncate to
acute, the nodes usually swollen (2) |
|
Basal sheaths purplish-red;
blades 3-16 mm wide ..... 2. C. nardus |
|
Basal sheaths whitish; blades 1.5-4
mm wide ..... 1. C. jwarancusa |
1. Cymbopogon jwarancusa (Jones)
Schult.
Iwarancusa Grass
Plants perennial. Culms to 150 cm, erect or geniculate; nodes often
swollen. Basal sheaths glabrous, smooth, whitish-green; ligules
2-6 mm, truncate to acute; blades to 30 cm long, 1.5-4 mm wide, whitish.
Inflorescences 15-40 cm, erect; rames 13-22 mm; internodes
and pedicels densely pilose on the margins and dorsal surface. Sessile
spikelets of heterogamous pairs 4.5-5.5 mm; lower glumes lanceolate,
shallowly concave distally, sharply keeled, keels not winged; upper lemmas
awned, awns 7-10 mm. Pedicellate spikelets about 6 mm. 2n = 20.
Cymbopogon jwarancusa is native to Asia, where it is grown for perfume and
as a medicine for fevers. It is grown as an ornamental in the United States, and
may persist for a considerable time after planting in the warmest parts of the
Flora region.
2. Cymbopogon nardus (L.) Rendle
Citronella Grass, Nardgrass
Plants perennial. Culms to 250 cm; nodes
often swollen. Basal sheaths glabrous, smooth, purplish-red; ligules
3-6 mm, acute; blades to 100 cm long, 3-16 mm wide, surfaces smooth or
scabrous. Inflorescences to 100 cm, linear, interrupted; rames
10-17 mm; internodes and pedicels pilose on the margins, glabrous
dorsally. Sessile spikelets of heterogamous pairs 3-4.5(6) mm; lower
glumes with narrowly winged keels; upper lemmas unawned or awned,
awns 6-10 mm. 2n = 20, 40, 60.
Cymbopogon nardus has been cultivated in the United States,but the variety
involved is not known. Cymbopogon nardus (L.) Rendle var. nardus,
which is native to Sri Lanka, is the common citronella grass. It differs from
C. nardus var. confertiflorus (Steud.) Stapf ex
Bor, which is native to both Indian and Sri Lanka, in having
unawned spikelets and 2n = 20, rather than awned spikelets and 2n
= 40, 60. Both varieties have been widely introduced beyond their native range.
3. Cymbopogon citratus (DC.) Stapf
Lemon Grass
Plants perennial. Culms to 200 cm, flexuous; nodes not swollen.
Basal sheaths closely overlapping, gaping at maturity, forming somewhat
flattened fans, glabrous, strongly glaucous; ligules 0.5-2 mm, truncate;
blades to 90 cm long, 6.5-15 mm wide. Inflorescences to 60 cm, nodding;
rames 10-25 mm; internodes and pedicels pilose on the margins
and dorsal surface. Sessile spikelets of heterogamous pairs 5-6 mm; lower
glumes shallowly concave below, flat distally, keels narrowly winged; upper
lemmas entire or bidentate, unawned or with a 1-2 mm awn. Pedicellate spikelets
4-4.5 mm, unawned. 2n = 40, 60.
Cymbopogon citratus is now known only in cultivation, even in Asia. Young
shoots are used as a spice, and the oils are extracted for lemon oil. It has been
grown in Florida.