Sporobolus africanus (Poir.) Robyns & Tournay
Common names: rat’s tail dropseed, rat’s tail grass, rush grass, tough dropseed (Eng.); fynsaadgras, saadgras, taaipol, vleigras, rotstert, taaipolfynsaadgras (Afri.); matshiki (isiZulu)
Sporobolus africanus is a tough, palatable, perennial grass with a low leaf production. It is a good indicator of disturbed veld.
Sporobolus africanus is a fast-growing, tufted, rhizomatous perennial grass, growing from 280–1 500 mm high. Its roots are fibrous.
The leaf blade is 200–400 × 1–4 mm; blade rolled in the bud, slender, stiff. Leaves are reasonably strong and difficult to break, leaf sheaths are hairless and slightly compressed. The dark, slightly green inflorescence is a dense, elongated, almost spike-like panicle. Branches are not whorled, relatively short, rigid, central axis usually visible. The panicle is 100–350 mm long, 10–40 mm wide, with a pointed tip.
Spikelets 2.0–2.8 mm long, with unequal outer glumes closely arranged along the panicle branches; lower glume 1/4–1/2 as long as spikelet, broadly oblong, apex obtuse, nerveless; upper glume ½ the spikelet length, narrowly ovate, apex acute; lemma ovate-elliptic, apex acute, grain ellipsoid, 1.1–1.2 mm long; anther 0.8–1.0 mm long. Seed brown, sub-lobular, and tiny, about 1 mm diameter. It flowers from autumn to early summer, from April to October.
In the Red list of South African plants, Sporobolus africanus is categorized as Least Concern (LC). It is not threatened, although it might face the risk of a declining wild population because of its medicinal use.
Sporobolus africanus has naturalised in Hawaii, New Zealand and Australia and is regarded as a serious invasive weed in Australia, where it is known as Paramatta Grass.
Distribution and habitat
Sporobolus africanus is mainly found in southern Africa to East Africa, as far as Ethiopia, and in Cameroon and Arabia. It is very widespread in South Africa, occurring in Limpopo, Northwest, Gauteng, Mpumalanga, Free State, KwaZulu-Natal and the Northern, Western and Eastern Cape Provinces. It also occurs in Namibia, Botswana, Swaziland, Mozambique and Lesotho.
This grass species grows in disturbed places, such as road reserves and trampled veld, as well as near water, beside streams and in other damp places. It is mostly found in compacted damp soils, such as near water points or kraals and in wet swampy soil. It often becomes dominant in open sunny areas.
Derivation of name and historical aspects
The genus name Sporobolus means ‘seed thrower’ and is derived from ancient Greek, sporos, meaning ‘seed’ and bolos, meaning ‘throwing’, from which arises the common name ‘dropseed grass’, referring to the dispersal of seeds, where the ripe seeds are pushed from the glume. The species name africanus means ‘from Africa’.
The genus Sporobolus has about 160 species, occurring in tropical and warm temperate regions; 38 species are found in southern Africa where they are widespread.
Sporobolus africanus is a self-pollinated grass and a prolific seeder. The only means of spread is by seeds. At maturity the seeds become sticky when damp, they stick to the outer surface of the glumes and thereafter seeds will attach to anything that brushes against them, such as animal fur, clothes and machinery. Some seeds also spread in mud, sticking to the hooves of animals, shoes and tyres. As a result, this species tends to spread along roadsides and animal tracks. Seeds are also dispersed in flowing water. Birds eat the seeds.
Rat’s tail dropseed has strong leaves and is seldom grazed. Grazing only takes place when the plant is young and where the concentration of grazing animals is high. Despite its low leaf yield and coarseness, it can provide valuable grazing even in autumn. Its presence usually indicates overgrazed and disturbed fields. Its dominance in veld can be seen as an indicator of trampled soil. Sporobolus africanus is used in traditional medicine, applied to wounds and snake bites.
Growing Sporobolus africanus
Sporobolus africanus is easily propagated from seeds. Seeds germinate in spring, the young seedlings will develop rapidly, producing flowering stems in mid to late summer. It produces immense quantities of seeds, for example, an average of 300 seeds per inflorescence. Established plants grow rapidly from the crown during the warmer months but growth rate slows in late autumn. Most of the seeds are produced during the warm seasons. Soil seed bank builds up quickly and seeds remain viable for a long time.
- Fish, L., Mashau, A.C., Moeaha, M.J. & Nembudani, M.T. 2015. Identification guide to southern African grasses. Strelitzia 36: 271–276. South African National Biodiversity Institute, Pretoria.
- Fish, L. & Victor, J.E. 2005. Sporobolus africanus (Poir.) Robyn’s & Tournay. National Assessment: Red List of South African plants version 2017.1. Accessed on 28/05/2019.
- Global Invasive Species Database. 2019. Species profile: Sporobolus africanus. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1587 on 04-06-2019.
- Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Moffett, R. 1997. Grasses of the eastern Free State: their description and uses. UNIQWA, Phuthaditjhaba.
- Parsons, W.T. & Cuthbertson, E.G. 2001. Noxious weeds of Australia. CSIRO publishing, Australia
- Retief, E. & Herman, P.P.J. 1997. Plants of the northern provinces of South Africa: keys and diagnostic characters. Strelitzia 6. National Botanical Institute, Pretoria.
- Van Oudtshoorn, F. 1999. Guide to the grasses of southern Africa. Briza Publications, Pretoria.
Creselda Nyeleti Shirinda and Aluoneswi Caroline Mashau
National Herbarium, Pretoria
Acknowledgements: Images not taken by the authors as follows:
Sporobolus africanus growing in Hawkes Bay, New Zealand by Colin Meurk, posted on iNaturalist.org.
Sporobolus africanus inflorescence and plant in flower, by Chris Whitehouse, posted on iNaturalist.org.
Plant Type: Grass
SA Distribution: Eastern Cape, Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, North West, Northern Cape, Western Cape
Soil type: Sandy, Clay, Loam
Flowering season: Spring, Early Summer, Autumn, Winter
Flower colour: Green
Aspect: Full Sun, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Easy