Cortaderia species

(Pampas Grass)

Three species of Pampas grass (Cortaderia) have become environmental weeds in Australia, but Cortaderia jubata (Pink pampas grass) is the most aggressive of the three. It is the most common weedy Cortaderia in NSW and Victoria, and is replacing White pampas grass (Cortaderia selloana) as the major weedy Cortaderia in Tasmania. The other species is Cortaderia richardii which is only found in Tasmania.

Pampas grass is a declared weed in Tasmania, so its sale or distribution is illegal and landholders have a responsibility to eradicate it from their land. http://www.dpiw.tas.gov.au/

It is a Category W2 noxious plant in many regions of NSW and a declared weed in South Australia, and legislation also applies in West Australia.

The plant is a native to Argentina, Bolivia, Ecuador and Peru.

The map shows the distribution of Cortaderia jubata in Australia. As can be seen, it has naturalized in West Australia as well as South Australia, Victoria, Tasmania and New South Wales, and has considerable potential to spread. Map and image courtesy of www.weeds.org.au

Pampas grass is highly invasive and forms dense stands that excludes most other groundflower and prevents seed germination of larger shrubs and trees.

Individual flower heads can contain up to 100,000 seeds and their viability exceeds 75%.

Description

Pampas grass is a very large tussock forming perennial, with clumps becoming as big as 4.5 metres wide and high. The leaves are broad and about 2 metres long. They have sharp edges of forward-facing short teeth.

The plume-like flower heads can be up to .9 metres in length, and are held well above the leaves. The colour of the flower head of C. jubata varies from pink to pale purple and fades with age. The leaves of C. jubata are arching, whereas Cortaderia selloana (shown here, photograph courtesy of Tim Rudman, DPIWE) has white flower heads and erect leaves.

Pampas grass can turn up just about anywhere. It grows in well drained, sunny areas, such as roadsides, as well as damp, shaded places such as along streams and rivers and in forest. Coastal heath and dune systems are also vulnerable to invasion.

Dispersal

Seed is wind borne and can travel many kilometres. The plant is also spread from garden waste dumped into bushland and along stream banks.

Control

Pampas grass roots can grow to a depth of 3 metres, with a spread of up to 4 metres, so not only are they are very drought tolerant, mature plants often require backhoes and excavators to remove.

Smaller plants can be removed by hand, taking care to remove all the rhizome (underground stem).

A non-selective herbicide such as glyphosate can be sprayed, but is best applied after slashing foliage, then spraying regrowth when it reaches about 20 cm in length.

Sources of information:
www.weeds.org.au
Bush Invaders of South-East Australia, by Adam Muyt (R.G. and F.J. Richardson publishers)
Environmental Weeds - A Field guide for SE Australia, by Kate Blood, published by CH Jerram Science Publishers.

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