Imperata cylindrica
Imperata cylindrica (L.) Raeusch.
Family: Poaceae
Common names: silver-spike, cogon grass, cottonwool grass, beady grass, bedding grass, Ramsammy grass, river grass, silky grass, susenke, sword grass (Eng.); donsgras, sygras, beddingsgras, lalanggras, palinggras, silweraargras (Afr.); kxokwane, mohlaba-lerumo, mohlorumo, mothlorumo, qheme, tlhoromo (Sesotho); umthente (isiZulu)
Introduction
Silver-spike or cogon grass has a distinctive flowerhead, which is silky-white or cream and shaped like a cylindrical plume. The leaves are hard, rigid and spear-like.
Description
Description
Imperata cylindrica is a perennial grass, growing 100–1 200 mm high, with strong rhizomatous roots. The leaf blade is up to 1 500 × 2–12 mm, broad in the middle, narrowed at the apex and base, reddish in winter. The inflorescence is a dense, cylindrical, spike-like panicle, white to silvery due to long silky hairs. The spikelet is 3–6 mm long, awnless; the glumes (leaf-like structures at the base) are as long as the spikelet; and the anthers are 3.0–3.5 mm long. Imperata cylindrica flowers almost throughout the year, from August to June.
Conservation Status
Status
The conservation status of the Imperata cylindrica according to the South African National Biodiversity Institute (SANBI) Red List of South African plants, has been assessed as Least Concern (LC).
Distribution and habitat
Distribution description
Imperata cylindrica is a widespread grass, occurring in southern Africa and throughout the greater part of the warm temperate, subtropical and tropical parts of the Old World, extending to the Mediterranean and Asia. In South Africa it is dominant and mainly found in Limpopo, North West, Gauteng, Mpumalanga, Free State, KwaZulu-Natal and the Eastern, Northern and Western Cape provinces. It also occurs in Namibia, Botswana, Lesotho and Eswatini (formerly Swaziland).
Silver-spike grass grows in poorly drained, damp soil such as vleis and riverbanks where it can form dense stands. It also grows in other habitat types in areas with high rainfall.
Derivation of name and historical aspects
History
The genus Imperata is named after a botanist, Ferrante Imperato, who lived in the sixteenth century in Naples, Italy. Cylindrica is Latin for ‘cylindrical’, possibly describing the shape of the flowerhead.
The genus Imperata has 8 species, cosmopolitan in tropical and subtropical regions; 1 species occurs in southern Africa: Imperata cylindrica, where it is a widespread grass.
Ecology
Ecology
Imperata cylindrica forms dense stands in poorly drained soils, along riverbanks and in vleis and seasonally wet places. Imperata cylindrica is a prolific seed producer with one plant capable of producing up to 3 000 seeds. These are dispersed by wind over long distances. It also spreads by rhizomes (root-like stems), which can be transported by tilling equipment and in soil transport. It rapidly invades new areas, outcompeting the native vegetation and may cover very large areas of ground, and flourishes particularly well in grasslands that are frequently burned. It regrows vigorously after fire, often spreading freely to take over the burnt areas.
Uses
Use
Silver-spike grass is poorly utilised by animals due to the general hardness of the leaves. It is not used for grazing but is an important soil stabiliser. Imperata cylindrica is said to protect 16 million hectares of old, neglected, cultivated lands in the cleared rainforests of Indonesia from soil erosion. However, it can become an aggressive weed as rhizomes make it difficult to eradicate. It is used for thatching in Mozambique, but also as paper, fuel and as an ornamental in gardens. In Lesotho the raw rhizomes are eaten by shepherds and is also a remedy for children with a chest cold. It is a weed in tropical parts, especially in cultivated lands where rice, cotton, coffee and tea are cultivated.
Growing Imperata cylindrica
Grow
Imperata cylindrica can be propagated from seed by sowing on the surface in containers. The seed germinates quickly. Prick out the seedlings into individual pots when they are large enough to handle and plant them out when about 10 cm tall. Divide as the plant has new growth. Division is very easy and can be carried out at almost any time of the year.
Imperata cylindrica is a plant of the tropics and subtropics, where it is found at elevations up to 2 000 m. It grows best in areas where annual daytime temperatures are within the range 25–35°C, but can tolerate 20–40°C. It prefers a mean annual rainfall in the range 500–3 500 mm but tolerates 250–6 250 mm. It grows well in ordinary garden soil in sun or partial shade. It prefers a pH in the range 4.5–6.0, tolerating 4.0–7.5. Established plants are drought tolerant. Although it has a wide range of useful attributes, silver-spike grass is also a widespread weed of disturbed ground and cultivated areas. Indeed, it is considered to be one of the 10 most noxious weeds in the world. It spreads vigorously by its rhizomes, which penetrate deep into the soil and are almost impossible to eradicate.
References
- Bodley, D. 2024. Observation of Imperata cylindrica, Summerstrand, Gqeberha, South Africa. iNaturalist. Online. https://www.inaturalist.org/observations/208652446.
- Dzerefos, C.M. 2024. Observation of Imperata cylindrica, Bojanala, North West. iNaturalist. Online. https://www.inaturalist.org/observations/222092494.
- 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.
- Johnstone, R. 2019. Observation of Imperata cylindrica, Richards Bay, KZN. iNaturalist. Online. https://www.inaturalist.org/observations/177670623.
- Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Raimondo, D., Von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. & Manyama, P.A. (eds) 2009. Red list of South African plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.
- Useful Tropical Plants. Imperata cylindrica. https://tropical.theferns.info/viewtropical.php?id=Imperata+cylindrica. Accessed 09/07/2024.
- Van Oudtshoorn, F. 1999. Guide to the grasses of southern Africa. Briza Publications, Pretoria.
- Wehrlin, K. 2024. Observation of Imperata cylindrica, Sandpit, Greyton, Western Cape. iNaturalist. Online. https://www.inaturalist.org/observations/211101360.
Credits
Aluoneswi Caroline Mashau
National Herbarium, Pretoria
August 2024
Acknowledgements: images by Debbie Bodley, C.M. Dzerefos, Richard Johnstone and Klaus Wehrlin.
Plant Attributes:
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, Late Summer, Autumn, Winter, Sporadic/All year
PH: Acid, Neutral
Flower colour: White, Cream
Aspect: Full Sun, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Easy
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