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Cortaderia selloana

Robust, perennial grass, up to 2,5 m, rhizomatous, with large whitish-silver plumes.

Scientific name: Cortaderia selloana (Schult. & Schult.f.) Asch. & Graebn.

Common names: pampas grass, silver pampas grass

Family: Poaceae (Gramineae)

Status in Portugal: invasive species (listed in the Decreto-Lei nº 92/2019, 10 july)

Risk Assessment score: 26 | Value obtained according to a protocol adapted from the Australian Weed Risk Assessment (Pheloung et al. 1999), by Morais et al. (2017), according to which values above 13 mean that the species has risk of having invasive behavior in the Portuguese territory | Updated on 30/09/2017.

Synonymy: Arundo selloana Schult, Cortaderia dioica (Spreng.) Speg, Cortaderia argentea (Nees) Stapf, Arundo selloana Schult. & Schult., Gynerium argenteum Nees

Last update: 09/07/2021

Family: 
Poaceae (Gramineae)
Appearence: 
Grasses and herbs

How to recognise it

Perennial grass up to 2,5 m, rhizomatous, with a large rosette with basal leaves that may reach 3,5 m  diameter, with numerous culms that produce big panicles, that are either females or - in different individuals - hermaphrodite.

Leaves: greyish or bluish-green, linear, with razor sharp margins and an acuminate apex, forming a “v” when seen with a transversal cut.

Flowers: arranged in panicles, similar to large plumes, dense, whitish-silver (sometimes light violet), with 40-70 cm, being able to reach over 4m high.

Fruits: dark caryopses of 2-2,5 mm length.

Flowering: August to October.  

 

Similar species

Cortaderia jubata (Lemoine ex Carrière) Stapf is similar, but the panicle is looser and shows a more pinkish or dark violet colour; the culms are 2-2,5 times longer than the leaves’ rosette; the leaves are bright green to dark green.

 

Characteristics that aid invasion

It propagates by seed producing many seeds (a female plant may produce up to one million seeds), which are dispersed very efficiently by the wind, originating invasion foci in distant locations.

Native distribution area

Tropical part of South America (Chile and Argentina).

 

Distribution in Portugal

Mainland Portugal (Minho, Douro Litoral, Beira Litoral, Estremadura, Alto Alentejo, Baixo Alentejo, Algarve).

 

Geographic areas where there are records of Cortaderia selloana

Other places where the species is invasive

Europe (Spain, Italy, United Kingdom), western USA (California), Australia, New Zealand.

 

Introduction reasons

For ornamental reasons.

 

Preferential invasion environments

Coastal dunes, along roadsides and disturbed areas (wastelands and abandoned areas). It is an opportunistic species that establishes itself in areas where the native vegetation was eliminated or disturbed.

It adapts to a large variety of soils but it grows better in deep soils, with good drainage. It is frequently found in areas with a lot of sunlight that receive some humidity. It is sensitive to ice in the seedling stage, becoming more tolerant in maturation.

Impacts on ecossystems

It grows vigorously forming some dense stands that dominate grasslands and shrublands; it creates barriers to fauna circulation and uses available resources for other species.

Its razor sharp leaves may inhibit human circulation in invaded areas.

 

Economic impacts

Its control methodologies are quite expensive.  

 

Other impacts

Allergies.

The razor sharp leaves may injure people.

 

Natura 2000 Network habitats more subject to impacts

– Fixed coastal dunes with herbaceous vegetation («grey dunes») (2130);
– Dunes with Salix repens ssp. argentea (Salicion arenariae) (2170);
– Wooded dunes of the Atlantic, Continental and Boreal region (2180);
– Humid dune slacks (2190);
– Malcolmietalia dune grasslands (2230);
– DWooded dunes with Pinus pinea and/or Pinus pinaster (2270);
– Inland dunes with open Corynephorus and Agrostis grasslands (2330).

Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control.

The control methodologies used for Cortaderia selloana include:  

 

Physical control

Hand pulling: preferential methodology for seedlings and young plants present in sandy soils. In more compacted substrates, hand pulling must be done in the rainy season as to facilitate the removal of the root system. It should be guaranteed that no large roots and/or rhizomes remain in the ground, once they recuperate easily. Hand pulling should be done with individual protection equipment once the leaves are very sharp.

Mechanical pulling: it is applied to larger plants. It should be guaranteed that no large roots and/or rhizomes remain in the ground, once they recuperate easily.

Cutting and removing the rhizomes: it is applied to larger plants each time hand pulling is not an option. The cutting may be done with a chainsaw or brushcutter. The removal of the root parts may be done by using manual and/or mechanical equipment. The cutting should be done with individual protection equipment, because that the leaves are very sharp.

Panicle cutting. It should be done before the seed dispersion. One should guarantee that no panicle is left uncut. The cut panicles should be removed from the location and put in double bags to be posteriorly destroyed or the await degradation.

 

Physical + chemical control

Cut stump method. The stems should be cut as close to the ground as possible and applied herbicide (active substance: glyphosate) on the new sprouts.

 

Chemical control

Foliar application of herbicide: Spray with herbicide (active substance: glyphosate) limiting as much as possible its application to the target species.

 

Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.

CABI (2012) Cortaderia selloana. In: invasive">Invasive species">Species Compendium. CAB International, Wallingford, UK. Available: http://www.cabi.org/isc/ [Retrieved 10/11/2012].

 

 

Global invasive">Invasive species">Species Database (2012) Cortaderia selloana. Available: http://www.issg.org/database/species/ecology.asp?si=373&fr=1&sts=sss [Retrieved 10/11/2012].

 

 

 

 

Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, Coimbra, 183pp.

 

 

 

 

Herrera M, Campos JA (2006) El carrizo de la pampa (Cortaderia selloana) en Bizkaia. Guia practica para su control. Diputacion Foral de Bizkaia, Bilbau, Spain, 43 pp.