|Mark L. Gabel|
Plants perennial; strongly rhizomatous.
Culms 10-150(217) cm, mostly erect and unbranched, usually with 3-4 nodes.
Leaves not aromatic; sheaths open, ciliate at the margins of the
collars; ligules membranous; blades of the basal leaves linear to
lanceolate, sometimes ciliate basally, those of the cauline leaves reduced. Inflorescences
terminal, cylindrical to conical panicles with an evident rachis; rachises
often with numerous long hairs; inflorescence branches 1-7 cm, usually
shorter than the rachises, with spikelets in unequally pedicellate pairs; disarticulation
below the glumes. Spikelets homogamous and homomorphic, unawned; calluses
very short, hairy, hairs 7-16 mm. Glumes equal to subequal, membranous,
3-9-veined, with hairs longer than the florets over at least the lower 1/2; lower
florets reduced to hyaline or membranous lemmas; upper florets bisexual,
lemmas, if present, hyaline, unawned; anthers 1-2, yellow to brown; stigmas
elongate, purple to brown; styles connate or free. Pedicels not
fused to the branch axes, terminating in cuplike tips. Caryopses ovate
to obovate, light to dark brown. x = 10. Named after Ferrante Imperato (1550-1625)
of Naples, an apothecary and author of a folio work on natural history.
Imperata has nine species and is widely distributed in warm regions of both hemispheres. Its economic importance is primarily negative, as both I. cylindrica and I. brasiliensis are weedy (Gabel 1989), but new shoots of both species are used for hay or grazing. Imperata is thought to be closely related to Miscanthus. One species is native to the Flora region, and two have been introduced.
Stamens 2, filaments not dilated at the base ..... 3. I. cylindrica
Stamens 1, filaments dilated at the base (2)
Panicles 7.5-14(17) cm long; lower branches 1-3.5 cm long, appressed; upper florets usually without lemmas; southeastern United States ..... 1. I. brasiliensis
Panicles 16-34 cm long; lower branches 2-5 cm long, divergent; both florets with lemmas; southwestern United States ..... 2. I. brevifolia
1. Imperata brasiliensis Trin.
Brazilian Bladygrass, Brazilian Satintail
Culms 22-98 cm. Ligules 0.5-1.7 mm; blades 3-13(19) mm wide, linear-lanceolate. Panicles 7.5-14(17) cm; lower branches 1-3.5 cm, appressed. Callus hairs 7-13 mm; glumes 2.4-4.5 mm; lower lemmas 1-3.4 mm long, 0.5-1.1 mm wide; upper lemmas usually absent, if present, about 1 mm long, 0.3 mm wide; stamens 1, bases of the filaments dilated; anthers 1.4-2.8 mm; styles 1.1-4.7 mm; stigmas 2.4-6.7 mm. 2n = unknown.
The current range of Imperata brasiliensis includes South America and Central America, Mexico, and Cuba. It is now thought to be established in the southeastern United States, although it is considered to be eliminated from Florida (Hall 1978); collections of Imperata made there since 1970 having proved to be I. cylindrica. The two species differ in the number of their stamens and the frequent absence of the lower lemma in I. brasiliensis.
Imperata brasiliensis is listed as a noxious weed by the U.S. Department of Agriculture. Burning stimulates its flowering; consequently many specimens have burned leaves.
2. Imperata brevifolia Vasey
Culms 51-129 cm. Ligules 0.7-2.9 mm; blades 7-14 mm wide, linear to lanceolate, abaxial surfaces smooth, adaxial surfaces sometimes densely pilose basally, otherwise scabrous. Panicles 16-34 cm, dense; lower branches 2-5 cm, divergent. Callus hairs 8-12 mm; glumes 2.7-4.1 mm; lower lemmas 2.5-3.9 mm, membranous, glume like; upper lemmas 1.4-2.4 mm, completely surrounding the ovary; stamens 1, filaments dilated at the base; anthers 1.3-2.3 mm, yellow to orange; styles 0.9-2.4 mm; stigmas 2.1-4 mm, purple to brown. 2n = 20.
Imperata brevifolia is native to wet or moist sites in the southwestern deserts from California, Nevada, and Utah to western Texas. Many of the populations that were used in developing the map no longer exist, but several post-1990 collections have been made in San Bernardino, Sonoma, Fresnoa, Santa Barbara, Butte, and Kern Counties of California. It also persists in the Grand Canyon National Park. Most collections from Nevada, Utah, and Texas were made before 1945, in sites that are now used for housing or agriculture.
Imperata brevifolia was listed as a noxious weed by the state of California. The reason for the listing is not clear; it may have stemmed from confusion of this native species with one of the introduced weedy species. In September 2003, Dr. Fred Hrusa succeeded in persuading the California authorities that Imperata brevifolia should be taken off the state's noxious weed list.
3. Imperata cylindrica (L.) Raeusch.
Culms (10)30-95(217) cm. Ligules 0.2-3.5 mm; blades to 150 cm long, (1)3-11(28) mm wide, linear-lanceolate, bases narrowed to the broad midrib, often with hairs on the margins. Panicles 5.7-22.3(52) cm, narrowly cylindrical; lower branches 1-3.2(7) cm, appressed. Callus hairs 9-16 mm; glumes 2.6-5.5 mm; lower lemmas 1.4-4.5 mm; upper lemmas (0.7)1.3-2.3(3.4) mm; stamens 2, filaments not dilated at the base; anthers (1.5)2.2-4.2 mm, orange to brown; styles 0.5-3.4 mm; stigmas 2.8-5.2(8.3) mm, purple to brown. 2n = 20, 40, 60.
Imperata cylindrica is the most variable species in the genus. Several varieties have been recognized but, although there are statistically significant differences between plants from different regions, identification to variety without knowledge of a plants geographic origin is risky. All North American plants examined have had 2n = 20.
Imperata cylindrica is one of the worlds 10 worst weeds, and is listed as a noxious weed by the U.S. Department of Agriculture. It was introduced to Alabama by 1912, and has spread considerably through the southeastern United States since then. The cultivar 'Red Baron' is diminutive and non-weedy, but individual shoots may revert to the aggressive form. Such reversion is particularly common in plants grown from tissue culture.