Invasiveness Assessment - Pink pampas grass (Cortaderia jubata) in Victoria

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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.

Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the invasiveness of Pink pampas grass.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
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Common Name: Pink pampas grass
Scientific name: Cortaderia jubata

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Generally germination occurs in spring (Bossard, Randell & Hoshovsky 2000).	MH	MH
Establishment requirements?	In shaded areas, seedling survival is reported to be low (Bossard, Randell & Hoshovsky 2000). Therefore seedlings are capable of establishing in moderate shade if only to a minor extent.	MH	MH
How much disturbance is required?	Able to invade chaparrel (Heathland) in California (Lambrinos 2000). Therefore it is able to invade healthy undisturbed ecosystems.	H	H
Growth/Competitive
Life form?	Large perennial tussock grass (Lambrinos 2000).	MH	H
Allelopathic properties?	There is evidence to suggest Cortaderia selloana contains phytotoxic substances which can inhibit germination (Chou & Young 1975). Unknown if C. jubata contains similar substances.	M	M
Tolerates herb pressure?	Cattle do graze the plant and grazing has been recommended for use as a control method in commercial forests (Harradine 1991). However this requires an intense grazing pressure, under lower levels control is not effective (West & Dean 1989). Grazing pressure from rabbits can reduce seedling establishment (Lambrinos 2006). Smaller plants do not persist under intense grazing pressure (Muyt 2001). Unknown however if plants are able to flower under moderate grazing.	M	MH
Normal growth rate?	Slow to start, fast once established, therefore competitive (Bossard, Randell & Hoshovsky 2000).	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Resilient to fire, as the meristem is insulated from the fire within the tussock (Lambrinos 2000). Once established can tolerate extended dry periods (Muyt 2001). This species has been reported to not tolerate drought (Bossard, Randell & Hoshovsky 2000). This may be more due to establishment requirements of seedlings than stress tolerance of an established plant. Can be damaged by frost, but the plant is not killed, therefore tolerant (Stanton & DiTomaso 2004). Able to germinate in disturbed seasonal wetlands (Lambrinos 2002).	H	MH
Reproduction
Reproductive system	Produces seed through apomixis and reproduces vegetatively through fragmented tillers, as no pollen is produced seed production through apomixis is also viewed as vegetative (Parsons & Cuthbertson 2001; Philipson 1978).	MH	H
Number of propagules produced?	On average annual viable seed production has been estimated to be almost 240,000 per plant (Drewitz & DiTomaso 2004).	H	H
Propagule longevity?	There is some doubt to how long seeds can remain viable, it is agreed not long and even suggested to be less than one year (Drewitz & DiTomaso 2004).	L	H
Reproductive period?	Plants are reported to be capable of surviving for 15 years (Bossard, Randell & Hoshovsky 2000).	H	MH
Time to reproductive maturity?	Can flower in first year (Parsons & Cuthbertson 2001).	H	MH
Dispersal
Number of mechanisms?	Seeds a very light, with most viable seeds being between 0.32 and 0.6 mg (Drewitz & DiTomaso 2004). Fine hairs on the lemma assist in wind dispersal (Knowles & Ecroyd 1985). Wind, water and human aided dispersal (Muyt 2001). Therefore more than one method of dispersal, with the main mode being wind, which is aided by the seeds light weight and fine hairs.	H	MH
How far do they disperse?	Reported to have invaded an uninhabited island 16 km off New Zealand’s north coast (Coulston 2002). Therefore seed is able to disperse potentially more than 16 km and therefore quite capable of dispersing more than 1 km.	H	H

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