Plants that invade bushland

Page last updated: Thursday, 11 December 2014 - 10:10am

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Pampas grass

Pampas grass (Cortaderia selloana) is not a practical choice for gardens because of its huge size and dangerously sharp leaves — in New Zealand, where it is a serious weed, its common name is cut-throat grass.

Large silvery plume-like seed head.
Pampas grass.

It has invaded sunny, swampy sites from Perth to Albany, where local councils made it the subject of an eradication campaign. Pampas grass could become a major weed of Western Australian wetlands. Each plume can hold up to 100 000 seeds, which the wind carries great distances.

Removing a large specimen from the garden is virtually impossible for the average gardener, who would need to wear protective overalls at the very least. Employing a back-hoe operator to dig it out is an alternative option.

A small specimen could be cut down to ground level and then, when regrowth reaches between 50cm and 1m, the new growth can be treated with a glyphosate-based herbicide. Do not attempt to burn out a plant close to a house or other important structure.

Sweet pittosporum

Sweet pittosporum (Pittosporum undulatum) is native to New South Wales, Queensland, Tasmania, and Victoria. It produces large quantities of orange berries that are eaten by birds, which then spread the seeds via their droppings.

Simply cutting it off at the base will only result in the stump resprouting, so the whole tree needs to be removed professionally.

Victorian tea-tree

The home range of Victorian tea-tree (Leptospermum laevigatum) includes New South Wales, Queensland, South Australia, and Tasmania. It was an early introduction to Western Australia, mainly for use as a hedge plant, especially in coastal settlements. Many coastal areas of southern Western Australia are now seriously threatened by dense monocultures of Victorian tea-tree. Seed is distributed by the wind, while stem layering facilitates further spread. 

In the garden, felling the tree should usually suffice to remove it, but it has been observed to resprout. If this happens, treat the stump and new shoots with a 'tree and blackberry killer' herbicide.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080