Updated: Corrected info about common name in Australia, as well as about sheep in that country. Thanks to a reader.
When I was visiting Cape Coral, FL, USA last year, I happened upon a very distinctive grass species that had an inflorescence that looked like drill points. Unfortunately, I did not have my camera with me, and the pics I took with my phone were too shabby to be used in the blog. I visited the area again last week during the Turkey holidays, and again saw the same species, but this time was able to take some pics.
I somewhat easily identified the species as Heteropogon contortus, which normally is considered native to Southern Africa, southern Asia, Northern Australia, Oceania, and southwestern North America. It is a dominant drought-tolerant perennial bunchgrass that has since spread to most tropical and subtropical regions of the world, its spread helped by the fact it can produce apomictic seeds.
Its common name is “tanglehead” in the mainland USA, but is called “pili” in Hawaii, where it is used in thatch huts, is considered native, and has been in a losing war against the invasive Cenchrus setaceus. The latter can produce 2-9 times more seed than the native, and whatever seeds are produced have a much higher germination rate (45% vs 13%). In addition, the invader recovered more quickly after burning or clipping (Goergen and Daehler, 2001).
In Australia, the species is commonly called “Black Speargrass”. H. contortus is an ecologically and economically important resident of tropical savannas, and it dominates the understory of Eucalyptus woodlands in tropical and subtropical regions of the country.
Its economic importance is in its value as a pasture species and in revegetation efforts, but it has also resulted in the destruction of the wool industry in many parts of Australia. The seeds become embedded in the wool and skin of the sheep, which devalues the resulting wool and can even kill the sheep (Grice and Macintyre, 1995).
The specific epithet of the species probably refers to the fact the seed twists or contorts when it dries, and the common name “Black Speargrass” at first also seems apt, but to be honest when I first started taking photos of the species, I thought that the tips of the inflorescence looked more like black drill bits to me. Either way, it’s one of the more recognizable grasses around, and I’m always happy to find species that don’t have just generalized panicles 😉
Literature Cited
Goergen, E., and C. C. Daehler. 2001. Reproductive ecology of a native Hawaiian grass (Heteropogon contortus; Poaceae) versus its invasive alien competitor (Pennisetum setaceum; poaceae). International Journal of Plant Sciences, v. 162, no. 2, p. 317-326.
Grice, A. C. and Sue McIntyre. Speargrass (Heteropogon Contortus) in Australia : Dynamics of Species and Community. Rangeland Journal 17 (1995): 3-25.
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