Taxonomic name: Cortaderia selloana (J.A. & J.H. Schultes) Aschers. & Graebn.
Synonyms: Arundo selloana Schult. and Schult. f., C. argentea (Nees) Stapf, Cortaderia dioica (Spreng.) Speg., Gynerium argenteum Nees
Common names: herbe de la pampa (French-France), pampas grass, silver pampas grass, silwergras (Afrikaans), Uruguayan pampas grass
Organism type: grass
Cortaderia selloana is a tall tussock grass that can reach heights of 4 metres. It is found in subtropical regions in habitats such as disturbed areas along roads and trails. It forms dense stands that can exlude other plants and quickly become a fire hazard, and its sharp leaves can cut skin and limit recreational use. It is often planted as an ornamental, and is also used as a wind barrier along highways and fodder for stock. A combination of physical and chemical control is required to manage this species.
Cortaderia selloana is a robust, tussock grass that stands up to 3.5m in diameter, and has flowering stalks that can reach upwards of 4m in height. The leaves are gray or bluish-green with narrowly tapering tips. The leaves are also bristle-like with the blade often forming a v-shape when viewed as a cross section. The margins are rough and somewhat cutting, and the leaves are mostly basal to two-thirds of the height of the flowing stalks. The inflorescence can be described as a silver or white with heavy branching and a feathery appearance, and is 400-700mm long (PIER, 2002).
coastland, ruderal/disturbed, water courses
In its native range, in South America Cortaderia selloana grows in relatively damp soils and along river margins. C. selloana is found along streams and in the low wet areas of Argentina and southern Brazil. In its introduced range C. selloana can be found in sub-humid and semi-arid subtropical regions. Pampas is capable of becoming established on a wide variety of soil types. Deep soil with good drainage gives best growth results. It is often found in open sunny places which receive added moisture, becoming naturalised as a weed in damp places, depressions, along stream banks, the margins of mangrove swamps and, in particular, disturbed areas associated with roads, pipeline cuts and walking trails in forest areas and waste places. Knowles and Ecroyd (1985) state that pampas is sensitive to frost at the seedling stage but will become more frost tolerant with age.
Cortaderia selloana can form dense stands that exclude other plants. Its sharp leaves cut skin and can limit recreational use of areas, and it can form dense colonies that can become or increase fire hazards (May et al., UNDATED). Once seedlings become established, it is a substantial threat to the ecological quality of preserves, particularly in coastal and grassland sites due to competition with native plants. Its rapid growth and accumulation of above ground and below ground biomass allow it to acquire light, moisture, and nutrients that would be used by other plants. It can be damaging even at low densities because of the amount of cover it can occupy (Starr et al. 2003). Studies comparing C. selloana with Cortaderia jubata a similar species found that C. selloana is genetically more diverse and could be one of the reasons of its success (Lambrinos, 2001).These results are consistent with the hypothesis that genetic variability enables better utilisation of heterogeneous habitats as well as promoting greater competitive abilities. In California, C. selloana inhabits a greater range of environmental conditions expanding into continental climatic zones.
The rapid spread of pampas into exotic forests in New Zealand is a particular problem due to it's competition with pine, fire hazard, reduced accessibility and cost of control (Gadgil et al., 1984). Also the great quantity of fluffy seed has caused problems for kiwifruit growers since it clings to the fruit and causes it to be rejected for exprot (Knowles and Tombleson, 1987).
Cortaderia selloana is a vigorous ornamental grass widely used as a lawn specimen, but its quick growth rate and large size make it unsuitable for most home landscapes (Gilman, 1999). However, it is ideal for barrier or windbreak plantings and has a place in larger areas such as along highways or in commercial or industrial landscapes. C. selloana has been used to control erosion in serpentine soils (Danielsen et al. 2003). Selected strains were produced and used from the 1930's in New Zealand as a supplementary fodder for cattle (Lynch and Osborne, 1948)
Native range: South America (USDA-GRIN, 2003).
Known introduced range: Australia, New Zealand, and North America (PIER, 2002). South Africa (Starr et al. 2003).
Introduction pathways to new locations
Agriculture: Cortaderia selloana has value as fodder (Gadgil et al., 1984)
For ornamental purposes: Cortaderia selloana is a vigorous ornamental grass widely used as a lawn specimen (Gilman, 1999).
Other: Cortaderia selloana is ideal for barrier or windbreak plantings and has a place in larger areas such as along highways or in commercial or industrial landscapes (Gilman, 1999).
Local dispersal methods
Agriculture (local): 2,426,360 plants distributed for fodder throughout N.Z (Jaques, 1957)
For ornamental purposes (local): Cortaderia selloana is a vigorous ornamental grass widely used as a lawn specimen (Gilman, 1999).
Natural dispersal (local): Cortaderia selloana reproduces by seed and is wind dispersed.
Preventative measures: A Risk assessment of Cortaderia selloana 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 24 and a recommendation of: reject the plant for import (Australia) or species likely to be a pest (Pacific).
Physical: Seedlings and small plants can be hand pulled or dug up especially in loose ashy soils. It is somewhat harder to pull or dig up in lava and compounded soils. Larger plants can be removed by heavy machinery. Care should be taken to contain any seeds or flowering stalks and these should be double bagged and disposed of in the garbage or left on site. Workers should take care to protect themselves when manually removing Cortaderia as it has sharp serrated leaves that can cut unprotected skin (Starr et al. 2003). Care should also be taken that all rhizomes are removed so there is no re-establishment.
Chemical: Chemical control is resorted to when mechanical removal cannot be employed. Foliar applications of Roundup (4% solution) or Roundup Pro (2% solution) (any glyphosate product) are effective in controlling pampas grass (Starr et al. 2003). Plants should be sprayed until wet but not to the point of run off. In wild areas, aerial spray by helicopter is employed. Leaving plants in place after spraying will result in less disturbance and may help reduce subsequent seedling germination in the area. May et al. (UNDATED) suggest removing the foliage first through cutting or burning, and then treating the re-growth with a post-emergence herbicide.
Cortaderia selloana succeeds in most soils, preferring a damp well-drained sandy or loamy soil. It is inclined to be intolerant of cold clay soils. It succeeds in dry soils. C. selloana prefers a sunny sheltered position, and is very tolerant of maritime exposure (Plants for a Future, 2000)
Cortaderia selloana reproduces by seed. Seeds are primarily wind-dispersed and are capable of dispersal distances up to 20 miles (Starr et al. 2003). C.selloana is gynodioecius but behaves dioeciously in nature (Knowles and Ecroyd, 1985). Female seeds have long fine hairs on the lemma making it ideal for wind dispersal. Hermaphrodite seeds don't have these hairs (McGlone MSc thesis, 2003). Female plants are capable of producing up to 100 000 seeds per flowerhead (Ecroyd et al. 1984)
Cortaderia selloana is a perennial tussock. Flowering begins in late summer - early autumn and are capable of flowering in the first season from seed (Connor, 1974)
Reviewed by: Mrs Heidi Pene (Msc), Pest Plant Contractor to Environment Waikato.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Wednesday, 22 February 2006