issg Database: Ecology of Pennisetum clandestinum

Pennisetum clandestinum (grass)

Kikuyu grass seeds are 1.5-2.5 mm in length (Photo: USDA APHIS PPQ Archives, USDA APHIS PPQ, www.forestryimages.org) - Click for full size

Taxonomic name: Pennisetum clandestinum Hochst. ex Chiov.

Synonyms: Pennisetum inclusum Pilg., Pennisetum longstylum Hochst., Pennisetum longstylum var. clandestinum (Hochst. ex Chiov.) Leeke

Common names: capim-quicuio (Portuguese), kikuyo (Colombia, Peru, Uruguay), kikuyu grass (English-Australia, Eastern Africa, Hawaii, India, Jamaica, Philippines, United States), kikuyu pul (Tamil-Sri Lanka), kikuyu tana (Sinhalese-Sri Lanka), kikuyugras (German-Germany), pasto africano (Spanish), West African pennisetum (English), xi fei lang wei cao (Chinese-China)

Organism type: grass

Pennisetum clandestinum is a creeping, mat-forming grass that originates from tropical eastern Africa. It gets its common name, kikuyu grass, from the fact that it is native to the area in which the Kikuyu tribe live. Pennisetum clandestinum is an aggressive invader of pasture, crops and natural areas. It spreads via an extensive network of rhizomes and stolons, and smothers all other vegetation. It is difficult to control manually, but the use of herbicides can yield good results.

Description
Pennisetum clandestinum can be distinguished by its extensively creeping rhizomes and stolons which form a dense mat, its culms with overlapping leaf sheaths and by its flowers which, if present at all, appear on leafy, vegetative side shoots with only the stamens visible above the leaf sheaths. This species grows prostrate with rooting from the nodes, internodes short, profuse vertical leafy branches arise from the stolons and rhizomes; blades narrow, spreading, blunt to pointed, 1.25 to 5cm long, 3 to 4mm wide, folded at first, later flat, the margins rough. The small white or tawny panicles are not borne at the top of the culms as in other grasses but are enclosed within short leaf sheaths at the top of short side shoots which resemble regular vegetative shoots. The seeds can be found only by dissecting the leaf sheaths. (Holm et al. 1977).

Similar Species
Cynodon dactylon, Stenotaphrum secundatum

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Occurs in:
coastland, natural forests, range/grasslands, ruderal/disturbed, urban areas, wetlands

Habitat description
Pennisetum clandestinum is usually found within the latitudes 35°N to 37°S. It grows at up to 3000m in dry and mesic habitats (Holm et al. 1977). It will invade wet environments when the forest is disturbed (Smith, 1985 in PIER, 2003). Grows best in moist, humid conditions. Particularly invasive in coastal areas (Environment BoP, 2003). Intolerant of dense shade, so is not a major problem in established forest areas, although can form the dominant understorey in forest margins and plantation crops (Holm et al. 1977). Usually needs more than 900mm of annual rainfall (DPI, 1999), but is able to survive long periods of dry weather if well-established. Requires soils with good drainage (FAO, 2003). Can tolerate a light frost, but will not survive sustained cold weather (FAO, 2003). Grows best at temperatures bewteen 21°C and 40°C (CDFA, 2003). Able to withstand frequent and severe defoliation eg. through mowing or overgrazing (Holm et al. 1977).

General impacts
Under certain conditions P. clandestinum can accumulate high levels of soluble oxalates and nitrates that are toxic when eaten by livestock (CDFA, 2003). Can invade areas of turf, such as golf courses and lawns (Haubensak & Smyth, 1999). Forms mats, which inhibit regeneration by smothering seedlings. Also produces allelopathic chemicals that kill other plant species in its vicinity (Sanchez & Davis, 1969 in PIER, 2003). Invades agricultural areas and roadsides, and is able to climb over and smother shrubs and young trees (South Coast Weeds, 2003). In Peru, P. clandestinum has invaded ancient Inca ruins, causing destruction through its roots growing in crevices and cracking the stones (Environment and Conservation, 1999).

Uses
Soil stabilisation and erosion control (South Coast Weeds, 2003). A widely-used pasture grass for dairy and beef production (Holm et al. 1977). Can be used as turf on golf courses, but is high maintenance and may be considered a weed (StatMasters, 2003). Useful as a lawn grass (FAO, 2003).

Notes
On U.S. Federal noxious weed list (PIER, 2003). Regarded as a crop weed in 14 crops in 36 countries (Holm et al. 1977).

Geographical range
Native range: Tropical eastern Africa.
Known introduced range: many Pacific Islands, Australasia, China, Indonesia, Philippines, South Africa.

Introduction pathways to new locations
Agriculture: Used as a pasture grass (Holm et. al., 1977).
For ornamental purposes: Used as a lawn grass (FAO, 2003).
Translocation of machinery/equipment: Small pieces of rhizomes or stolon can be transported to new locations in weed clearing machinery (South Coast Weeds, 2003).

Local dispersal methods
Agriculture (local): Used as a pasture grass (Holm et. al., 1977).
Consumption/excretion: Although rarely produced, seeds are able to survive ingestion by sheep (CDFA, 2003).
For ornamental purposes (local): Used as a lawn grass (FAO, 2003).
Garden escape/garden waste: Dumping garden waste into bush areas assists spread (South Coast Weeds, 2003).
Natural dispersal (local): Aggressively spreads via rhizomes and stolons (CDFA, 2003).
Translocation of machinery/equipment (local): Small pieces of rhizomes or stolon can be transported to new locations in weed clearing machinery (South Coast Weeds, 2003).

Management information
Preventative measures: A Risk Assessment of Pennisetum clandestinum for Hawai‘i and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 18 and a recommendation of: "Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world."

A Risk assessment of Pennisetum clandestinum for Australia was prepared by Pacific Island Ecosystems at Risk (PIER) using the Australian risk assessment system (Pheloung, 1995). The result is a score of 12 and a recommendation of: reject the plant for import (Australia) or species likely to be a pest (Pacific).

Physical: Difficult to dig out as all rhizomes must be removed to prevent resprouting (PIER, 2003).

Chemical: Roundup (without Pulse) 1%, Dowpon 740-SP (16-20 g/l sater), Gallant (0.5%) (Timmins & Mackenzie, 1995 in PIER, 2003)
For large areas, graze or mow kikuyu grass right down before spraying the new growth with Roundup while it is still short. For areas that contain desirable species, spray with Gallant (Environment BoP, 2003). The application of methylarsonic acid (MSMA) and triclopyr may reduce the competitive ability of P. clandestinum, allowing desirable species to reestablish (Cudney et al. 1993 in Haubensak & Smyth, 1999).

Biological: A rust fungus (Phakopsora apoda) has become established in South Africa, but it appears to only decrease the photosynthetic capacity of the leaves and does not kill the plant (Adendorff & Rijkenberg, 1995 in Haubensak & Smyth, 1999). Two insect pests, Sphenophorus ventus vestitus and Herpetogramma licarsicalis, damage kikuyu grass in Hawai‘i (Cronk & Fuller, 1995 in PIER, 2003), and Mootooka et. al. (2002 in PIER, 2003) states that it is also susceptible to the yellow sugarcane aphid (Sipha sp.). Plants are also affected by a fungus disease caused by Pyricularia grisea, which kills seedlings (FAO, 2003).

Nutrition
Grows rapidly with high nitrogen levels, but will also respond well to phosphorus and sulfur on soils that are deficient. Often associated with volcanic soils and the red soils found in tropical and sub-tropical climates (Holm et al. 1977).

Reproduction
This species is tetraploid and spreads by underground runners (rhizomes) and stolons at the periphery of the main clonal patch (Haubensak & Smyth, 1999). PIER (2003) states that it can spread by wind-dispersed seeds although this is rare. Seeds are able to germinate in cow pats, after having passed through the animal's digestive tract (Wilson & Hennessy, 1977 in FAO, 2003). Regenerates well from rhizome fragments (PIER, 2003). Seed yield can be up to 500kg/ha from established swards (FAO, 2003).

Lifecycle stages
Seedlings can emerge from soil depths of around 6cm (CDFA, 2003).

Principal sources: Pacific Island Ecosystems at Risk (PIER)

Compiled by: IUCN/SSC Invasive Species Specialist Group (ISSG)

Shyama Pagad.

Last Modified: Friday, December 30, 2005