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Name

Panicum mindanaense

Merr.

This species is an annual and usually grows erect up to 1 m tall or is shortly spreading before becoming erect. The stems are hollow but not inflated or spongy at the base. Leaves are arranged at the base of the plant and along the stem (Fig. 1). The leaf blades are narrow, 3-18 cm long and 1.5-4.5 mm wide, densely hairy or hairless, smooth or rough to touch. Inflorescences or flowering branches terminate the stem and appear well above the leaf axils (Fig. 2). The inflorescences or flowering branches are large open panicles 7-30 cm long and 2-15 cm wide, with branches arising along a central stem (Fig. 2). Branches in the panicle are thin and lax, usually branch again and bear several spikelets (the basic flowering unit) towards the end of each branchlet. The spikelets consist of two glumes encompassing two florets (modified flowers), the upper floret with a hardened lemma which is seed like in appearance (Fig. 3), the lower floret is sterile.

 

Botanical Description

An annual species up to 1 m tall, erect, decumbent or ascending. The culms or stems are glabrous, leaf sheaths glabrous or sparsely covered with stiff tubercule based hairs. Leaf blades hairless, smooth or rough to touch, linear, 3-18 cm long, 1.5-4.5 mm wide. The inflorescences are open compound panicles (7-) 10-30 cm long, (2-) 6-15 cm wide (Fig. 2). Spikelets are 2.5-3 mm long, the lower glume 1.7-2.7 mm long, the upper glume 2-2.8 mm long, each tapered into a sharp point (acute to mucronate) (Fig. 3). The spikelets contain two florets as long as or slighter shorter than the spikelets, the lower floret is usually sterile and the upper floret is bisexual with a smooth, thick, hardened lemma, the lemma 1.4-2.8 mm long (Fig. 4).

 

Diagnostic Features

Separating species of Panicum takes careful observation of the spikelets and often comparison with herbarium specimens. Panicum mindanense can be most easily recognised by its small spikelet although this can be difficult to be confident with when you are not able to compare them with specimens of other species. Following Simon & Alfonso (2011) it can be identified from other species by the combination of the following characters: lower glume at least 3/4 spikelet length, lower floret usually sterile, spikelet between 2.5 and 3 mm long, and lower glume tapered to a sharp point. In this region spikelets are most similar to Panicum trachyrhachis and Panicum seminudum. From Panicum seminudum it is distinguished by the smaller spikelet, up to 3 mm in P. mindanaense and > 3 mm in P. seminudum, and the lower glume more or less equal to the spikelet rather than shorter. Differences with the Panicum trachyrhachis are discussed under that species. For a key to Australian species see Simon & Alfonso (2011).

 

Panicum species are usually recognisable by their open, spreading, often compound flowering heads, with a sparse distribution of spikelets towards and at the end of the branches. Spikelets are small and oval in shape and contain a small hard textured bisexual floret inside which is seed like in appearance (Fig 4). They can be easily confused with some species of Whiteochloa, Yakirra and Arthragrostis, and Megathrysus maximum (Guinea Grass). From Megathrysus maximum they can be distinguished by the smooth surface of the bisexual lemma (Fig. 4) which in Megathyrsus is wrinkled in appearance (Fig .5). From species of Whiteochloa and Arthragrostis they can be distinguished by the spikelet shape. Panicum spikelets are generally dorsally compressed, i.e. somewhat flattened from front to back so that the spikelet is widest across the back. Both Whiteochloa and Arthragrostis are considered laterally compressed, flattened from side to side, so that the spikelet is widest in side view (Fig. 6a & b). Also in Panicum the rhachilla or stem between the glumes and florets in the spikelet is not easily visible when dissected, whereas it is prominent (under magnification) between glumes and between florets in Whiteochloa, Yakirra, and Arthragrostis.

 

Habitat

This species is widespread in tropical Australia from Queensland through to Western Australia; also known from Southeast Asia. Usually found growing in tropical heaths, rainforests, woodlands and coastal grasslands, sometimes favouring moist places (Lazarides 2005, Simon 2011, Veldkamp 1996).

 

Land Management Notes

Panicum are economically important as fodder, food, and weed species, although no specific values are attributed to this species in the available literature (Anderson 2003, Lazarides 2002, Milson 2000, Rolfe et al. 1997).

 

Fig. 1. Herbarium sheet of Panicum mindanaense (MBA6638)
Fig. 1. Herbarium sheet of Panicum mindanaense (MBA6638)

 

Fig. 2. Inflorescence of Panicum mindanaense (MBA6638)  (scale bar = 1cm)
Fig. 2. Inflorescence of Panicum mindanaense (MBA6638)
(scale bar = 1cm)

 

Fig. 3. Mature spikelet of Panicum mindanaense (MBA6638) (scale bar = 1cm)
Fig. 3. Mature spikelet of Panicum mindanaense (MBA6638) (scale bar = 1cm)

 

Fig. 4. Smooth hardened lemma of Panicum mindanaense (MBA6638) (scale bar = 1cm)
Fig. 4. Smooth hardened lemma of Panicum mindanaense (MBA6638) (scale bar = 1cm)

 

Fig. 5. Wrinkled lemma of Megathrysus maximus (QRS73902) (scale bar = 1cm)
Fig. 5. Wrinkled lemma of Megathrysus maximus (QRS73902) (scale bar = 1cm)

 

Fig. 6a. Laterally flattened spikelet Whiteochloa airoides (QRS74296) (scale bar = 1cm)
Fig. 6a. Laterally flattened spikelet Whiteochloa airoides (QRS74296) (scale bar = 1cm)

 

Fig. 6b. Laterally flattened spikelet Arthagrostis clarksoniana (MBA8974) (scale bar = 1 cm)
Fig. 6b. Laterally flattened spikelet Arthagrostis clarksoniana (MBA8974) (scale bar = 1 cm)

 

 

Resources

Anderson, E.R. (2003) Plants of Central Queensland their identification and uses. Information Series Q103069, Queensland Department of Primary Industries.

Australian Tropical Rainforest Plants Edition 6 (2010) CSIRO: http://keys.trin.org.au/key-server/data/0e0f0504-0103-430d-8004-060d07080d04/media/Html/taxon/Panicum_mindanaense.htm. Accessed on 24 May 2017.

AVH (2017) Australia’s Virtual Herbarium, Council of Heads of Australasian Herbaria, <http://avh.chah.org.au>, accessed 30 May 2017.

Lazarides, M. (2002) Economic attributes of Australian grasses. Flora of Australia 43: 213-245.

Macfarlane, T.D. (1992) Panicum. In J.R. Wheeler (ed.), B.L. Rye, B.L. Koch & A.J.G. Wilson. Flora of the Kimberley Region. (Western Australian Herbarium, Dept. of Conservation and Land Management Como, W.A.), pp. 1195-1199.

Milson, J. (2000) Pasture plants of north-west Queensland. Information Series Q100015. Queensland Department of Primary Industries.

Rolfe, J., Golding, T. and Cowan, D. (1997) Is your pasture past it? The glove box guide to native pasture identification in north Queensland. Information Series Q197083. Queensland Department of Primary Industries.

Simon, B.K. & Alfonso, Y. (2011) AusGrass2, http://ausgrass2.myspecies.info/ accessed on [20 March 2017].

Veldkamp, J.F. (1996) Revision of Panicum and Whiteochloa in Malesia (Gramineae - Paniceae). Blumea 41(1): 199.