Synonym(s): Cortaderia dioica
Family: Poaceae (Grass Family)
Duration and Habit: Perennial Grass/Grasslike
C. selloana is a robust, tussock grass that stands up to 3.5 m in diameter, and has flowering stalks that can reach upwards of 4 m 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 400-700 mm long (PIER, 2002).
Ecological Threat: Cortaderia selloana is a tall tussock grass that can reach heights of 4 meters. It can be found in a variety of habitats from subtropical regions to disturbed areas along roads, and trails. It forms dense stands that can exlude other plants, and its sharp leaves can cut skin and limit recreational use. Because C. selloana has the ability to form dense stands it can quickly become a fire hazard. It is often planted as an ornamental, and also has uses as wind barriers along highways and fodder for stock. A combination of physical and chemical control is required to manage this species.
Biology & Spread: C. 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)
History: C. selloana has value as fodder is widely used as a lawn specimen and in larger areas such as along highways or in commercial landscapes (Gilman, 1999).
U.S. Habitat: In its native range, in South America C. 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 naturalized 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.
U.S. Nativity: Introduced to U.S.
Native Origin: South America
U.S. Present: CA, LA, SC, TX, UT
Distribution: Australia, New Zealand, and North America (PIER, 2002). South Africa (Starr et al. 2003).
List All Observations of Cortaderia selloana reported by Citizen Scientists
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.
Gilman, E. F. 1999. Cortaderia selloana. University of Florida, Cooperative Extension Service, Institute of Food and Agricultural Sciences: Fact Sheet FPS-145.
Starr, F., K. Starr, & L. Loope. 2003. Cortaderia spp.. United States Geological Survey: Biological Resources Division, Haleakala Field Station, Maui, Hawai'i.
PIER (Pacific Island Ecosystems at Risk), 2002. Cortaderia selloana
Ecroyd, CE; Knowles, B; Kershaw, DJ. 1984: Pampas - recognition of a new forest weed. What's-New-in-Forest-Research. 1984, No. 128, 6 pp.
Knowles, B; Ecroyd, C. 1985: Species of Cortaderia (pampas grasses and toetoe) in New Zealand. FRI Bulletin No. 105. New Zealand.
Global Invasive Species Database (http://www.issg.org/database)
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