Description: Tufted or stoloniferous perennials or annuals; culms often branched.
Leaves with ligule a rim of short hairs or rarely membranous; blade rolled or folded in bud, flat, folded, or convolute, often hairy.
Inflorescence a dense, spike-like panicle, sometimes reduced and enclosed by the sheaths.
Spikelets solitary or in groups of 2–4, surrounded by an involucre of bristles that falls with the spikelets (except in some cultivated varieties); florets 2, the upper bisexual, the lower male or sterile. Glumes unequal, translucent, the lower shorter than the upper or absent; the upper shorter than or equalling the spikelet. Lemmas 2, often mucronate; the lower equal to the upper glume or smaller and fewer-nerved, rarely reduced to a scale; upper lemma smooth, firm or papery, 5–15-nerved, with thin margins enclosing the palea. Paleas 2, subequal to the lemmas and of similar texture, 2-nerved.
Distribution and occurrence: World: c. 130 species, tropical & warm-temp. regions. Australia: 12 species (9 species naturalized), all States.
Many Pennisteum species are used for grain and forage while others are planted as ornamentals (e.g. P. setaceum); a number of species are weeds. P. glaucum, Pearl Millet, is a major food crop in warmer parts of the world and certain cultivars are planted for forage. Tall, densely tufted P. purpureum and hybrids with P. glaucum are used for windbreaks or cut forage. P. clandestinum, Kikuyu, a creeping species, is grown for pastures, lawns and playing fields. Key based on Vickery (1975). Recent research has shown that this genus is more appropriately amalgamated with Cenchrus - see Chemisquy et al. (2010) and references therein. We will be making this change once all of the relevant names have been published.
Text by S. W. L. Jacobs & S. M. Hastings (1993); edited KL Wilson (Sept 2010)
| ||Key to the species|| |
|1||Decumbent, stoloniferous and rhizomatous perennial; leaves with blade folded||Pennisetum clandestinum|
|Tufted annuals or perennials with well-developed spike-like panicles and flat or rolled leaves||2|
|2||Cultivated annual with stout culms and dense, cylindrical spike-like panicles with crowded spikelets that gape at maturity to expose the grain; bristles of the stalked involucre slender, persistent, about as long as the spikelets||Pennisetum glaucum|
|Perennials, cultivated or otherwise; panicle spike-like but not very dense, neither with crowded spikelets nor spikelets that gape at maturity; bristles prominent, deciduous, involucre stalked or sessile|
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|3||Tall, robust plants forming large tufts or bamboo-like clumps over 2 m high; leaves with blade 30–120 cm long and 1.5–4 cm wide; bristles of the subsessile involucre spreading or reflexed at maturity||Pennisetum purpureum|
|Tufts or clumps not as robust, rarely exceeding 1.5 m in height, leaves less than 1.5 cm wide, involucre spreading but not reflexed at maturity|
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|4||Inner bristles of the involucre plumose, involucre with a hairy stalk||5|
|Inner bristles of the involucre scabrous not plumose, involucre stalked or sessile|
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|5||Bristles of the inner whorl of involucre flattened at the base, forming a disc.||Cenchrus|
|Bristles slender throughout their length, neither flattened nor forming a basal disc|
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|6||Panicle 10–28 cm long, often purplish, involucre c. 2.6 cm long; spikelets to 6.5 mm long||Pennisetum setaceum|
|Panicle 2–12 cm long, pale green to white; involucre 3–5 cm long, spikelets 9–14 mm long|
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|7||Plants rhizomatous and tufted; spikelets 4–6 mm long; bristles of the subsessile involucre about as long as the spikelet except 1 that is longer and stouter; panicle pale-coloured||Pennisetum macrourum|
|Plants tufted; spikelets 6–8 mm long; bristles of the stalked involucre 2–5 times as long as the spikelets, inner bristles slightly longer than outer bristles; panicle usually purplish|
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