|David W. Hall|
John W. Thieret†
Plants annual or perennial; if perennial,
sometimes cespitose, sometimes rhizomatous or stoloniferous. Culms 15-300
cm, erect, sometimes decumbent. Leaves not aromatic; mostly basal; auricles
absent; ligules shortly membranous and ciliolate to ciliate or of hairs;
blades often rough and glaucous. Inflorescences terminal panicles
with elongate rachises and numerous branches, branches often naked for a considerable
distance before terminating in a rame; rames often with only a single heterogamous
triplet of 1 sessile and 2 pedicellate spikelets, sometimes with 1(-3) heterogamous
sessile-pedicellate spikelet pairs below the terminal triplet, internodes without
a translucent median groove; disarticulation oblique, below the sessile
spikelets. Sessile spikelets terete or laterally compressed; calluses
usually sharp, setose, hairs white or yellow to brown; glumes leathery
to stiff, involute or folded and keeled above; lower glumes rounded or
laterally compressed; lower florets sterile; upper florets bisexual,
unawned or awned. Pedicels slender, not fused to the rame axes, without
a translucent groove. Pedicellate spikelets dorsally compressed or absent,
if present, lower florets sterile and unawned, upper florets sterile or staminate,
awned or unawned. x = 5 or 10. Name from the Greek chrysos, golden,
and pogon, beard, an allusion to the yellow, bearded callus.
Chrysopogon is a tropical and subtropical genus of 26 species. All but one species are native to the Eastern Hemisphere tropics, the majority to India. Chrysopogon pauciflorus is native to Florida and Cuba; four species have been introduced in the Flora region.
Some species of Chrysopogon are ecologically or economically important outside the region, C. zizanioides being used for controlling soil erosion, C. fulvus for forage, and C. aciculatus for lawns. Chrysopogon aciculatus, however, is also an aggressive weed whose sharp calluses can pierce the stomach of grazing animals and get in the feet of soft-footed animals.
Upper lemmas of sessile spikelets awned, the awns 2-16 cm long (2)
Upper lemmas of sessile spikelets unawned or the awns no more than 8 mm long (3)
Plants annual; pedicellate spikelets 7.2-15 mm long ..... 1. C. pauciflorus
Plants perennial; pedicellate spikelets 2.5-8 mm long ..... 2. C. fulvus
Calluses of the sessile spikelets 0.6-0.8 mm long, rounded, with white hairs; plants not stoloniferous ..... 4. C. zizanioides
Calluses of the sessile spikelets 3-6.4 mm long, sharp, with golden-yellow hairs; plants extensively stoloniferous ..... 3. C. aciculatus
1. Chrysopogon pauciflorus (Chapm.) Benth.
Plants annual. Culms 60-110 cm, erect or somewhat decumbent. Sheaths glabrous; ligules membranous, ciliolate; blades to 31 cm long, 4-10 mm wide, flat or folded, mostly or completely glabrous, adaxial surfaces sometimes with scattered pubescence at the base. Panicles 20-30 cm, open; branches 5-8 cm, capillary, strongly divergent; rames usually a triplet of spikelets. Sessile spikelets 8.1-10 mm; calluses about 7 mm, sharp; glumes smooth below, scabrous distally; lower glumes shortly awned or mucronate from the sinuses of the minutely bilobed apices; upper lemmas awned, awns 10.6-16 cm, geniculate, twisted below. Pedicellate spikelets 7.2-15 mm. 2n = unknown.
Chrysopogon pauciflorus is native, but infrequently encountered, in the southeastern United States, primarily in Florida; it also occurs in Cuba. It grows in flatwoods, abandoned fields, pinelands, marsh edges, and various disturbed sites.
2. Chrysopogon fulvus (Spreng.) Chiov.
Plants perennial; cespitose, not stoloniferous. Culms 20-80(120) cm, geniculately ascending. Leaves mostly basal; sheaths glabrous; ligules 0.2-0.5 mm, membranous, ciliolate; blades 2-30 cm long, 2-3(9) mm wide, mostly glabrous or puberulous adaxially, bases sometimes with hispid hairs. Panicles 4-8(16) cm long, 1.5-3 cm wide, ovate, with many branches; branches 3-7 cm, sharply ascending, capillary, naked basal portions 2-6 cm, puberulous, terminating in a rame; rames with a triplet of spikelets. Sessile spikelets 3.5-5.2(8) mm (including the callus); calluses 0.7-1.5 mm, sharp, setose, hairs 1.5-1.9 mm, golden; lower glumes laterally compressed, smooth, hispidulous distally, acute; upper glumes with a dorsal fringe of hairs, awns 4.1-5.3(10) mm; upper lemmas awned, awns 2-3 cm, slightly geniculate, column twisted, puberulous, hairs 0.2-0.4 mm. Pedicels 1-2.5 mm, setose on the edges, hairs 3-4.9 mm. Pedicellate spikelets 2.5-8 mm; lower glumes muticous or awned, awns to 0.7 cm. 2n = 40.
Chrysopogon fulvus is native from southern India to Thailand, where it is considered a good forage grass. It was grown at the experiment station in Gainesville, Florida, and subsequently found in adjacent flatwoods as an escape.
3. Chrysopogon aciculatus (Retz.) Trin.
Mackie's Pest, Lovegrass
Plants perennial; extensively stoloniferous, with numerous sterile, leafy shoots. Culms 15-50 cm, often decumbent at the base, otherwise ascending or erect. Sheaths entirely or mostly glabrous, sometimes ciliate on the upper margins; ligules 0.1-0.3 mm, membranous, ciliolate; blades 1.5-11(23) cm long, 3-7 mm wide, adaxial surfaces mostly glabrous, or with a few papillose-based hairs near the base. Panicles 3-10 cm long, 1-3 cm wide, with many branches; branches 1.5-3.5 cm, stiffly ascending or appressed, naked lower portions 1.3-2 cm, terminating in a rame; rames 5-15 mm, with 1(-4) spikelet pairs. Sessile spikelets 7.5-9 mm (including the callus); calluses 3-6.4 mm, sharp, setose, hairs 0.4-1.1 mm, golden; lower glumes smooth on the lower portion, scabrous distally, acute or shortly bilobed; upper glumes mucronate, mucros 0.5-1.3 mm; upper lemmas awned, awns 4-8 mm, exserted, more or less straight. Pedicels 2-4 mm, mostly glabrous, hispidulous distally. Pedicellate spikelets 4.4-7.1 mm, staminate; glumes acute to acuminate; anthers 1.5-2.7 mm. 2n = 20.
Chrysopogon aciculatus is native to tropical Asia, Australia, and Polynesia. In the contiguous United States, it is known only from controlled plantings at the experiment station in Gainesville, Florida. It is a vigorous colonizer of bare ground that can withstand heavy grazing and trampling, and is difficult to eradicate once established. The sharp calluses are injurious to grazing animals. The U.S. Department of Agriculture considers C. aciculatus a noxious weed, and should be informed if the species is found growing in other than a controlled planting.
4. Chrysopogon zizanioides (L.) Roberty
Vetiver, Khus-Khus, Khas-Khas
Plants perennial; cespitose, not stoloniferous. Culms 1-3 m, not branched, not woody. Sheaths glabrous, keeled; Ligules 0.3-1.5 mm, of hairs; blades 23-140 cm long, 2.5-13 mm wide, flat or folded, mostly glabrous but the adaxial surfaces usually pilose basally. Panicles 16-33 cm long, 2.5-9 cm wide, with many branches; branches 5.5-12 cm, ascending, naked basal portions 1-4 cm, terminating in a rame; rames to 10 cm, with 5-13 spikelet pairs and a terminal triplet. Sessile spikelets 3.8-6 mm (including the callus); calluses 0.6-0.8 mm, rounded, laterally ciliate basally, hairs 0.1-1.4 mm, white; lower glumes scabrous or setulose to spinulose distally, particularly on the veins, acute to acuminate; upper glumes setulose distally, particularly on the veins, without a dorsal fringe of hairs, muticous; upper lemmas muticous to awned, awns to 2(4.5) mm, straight. Pedicels 2.2-4.3 mm. Pedicellate spikelets 2.8-4.6 mm, staminate; glumes muticous; anthers 1.6-2 mm. 2n = 20.
Chrysopogon zizanioides, which used to be included in Vetiveria Bory, is native to river banks and flood plains in the south Asian tropics and subtropics, but it has been deliberately established in the warmer areas of the United States. It grows in a variety of soils, from heavy clays to dune sand, and will tolerate windy coastal conditions.
Hedges of Chrysopogon zizanioides can control soil erosion or restore eroded land. Once established, they are effective even in desert areas subject to flash flooding. The deep root system reaches water far below the surface and prevents the plants from being washed away while the dense, aboveground growth traps silt and sediment. Because C. zizanioides does not spread vegetatively and many cultigens have low or no seed production, contour hedges can be planted around cultivated fields or engineering structures without fear of invasion.
Essential oils from the aromatic roots are sometimes used as perfume, and numerous biocidal effects are reported. For current information on uses of Chrysopogon zizanioides, see http://www.vetiver.org/.