Weeds

RBG Melbourne

After land clearing, invasive plant species present the greatest threat to biodiversity world-wide. Exotic invasions can have a negative impact on environmental and sustainability efforts and result in habitat degradation and species extinction which, in turn, affects our economy and society.

Weed control and lost production costs Australia’s primary industries in excess of $4 billion per annum.

The vast majority of Australia’s weeds are plants that were deliberately introduced for agriculture, forestry or horticulture but escaped from cultivation into the natural environment. It seems inevitable that many weeds of the future are already present in Australia and growing in our gardens today.

In Australia, the weed problem is being addressed through The National Weeds Strategy (1999) and national bodies such as the Cooperative Research Centre for Australian Weed Management are currently coordinating national projects related to weed research, awareness and management.

Weed control strategies and on-ground management are coordinated by State and Territory agencies. In Victoria, management of the risks posed by weeds is outlined in Victorian pest management: a framework for action: weed management strategy (2002) which was a follow-up to the Victorian Weed Strategy (1999).

RBG Melbourne has developed a Weed Strategic Plan to guide management of a range of issues. As part of this plan, a Weed Risk Assessment Procedure was developed to assess plants’ weed potential.  

Gardeners and horticulturists everywhere must play their part in protecting the environment by regularly monitoring weeds in their own backyards.

Weed Resource and Information Pack (MS Word - 1.16 mb)

How are weedy plants managed at RBG Cranbourne?

What is a weed?

A weed is a plant that is considered to be ‘out of place’. Environmental weeds are plants that invade bushland and threaten indigenous biodiversity.

Many current weed species were originally introduced to Australia during European settlement, either accidentally or deliberately, for horticulture, agriculture and forestry. Their ability to adapt to new conditions and vigorous reproduction methods has enabled them to become well established.

The potential still exists for new environmental weeds to be introduced into Australia. If introduced to Australia, these species will invade natural systems and displace indigenous plants.

Seed and plant material can also be spread by humans, animals, machinery, and through the inappropriate disposal of garden waste.

Native species also have the ability to become weeds if they become established outside of their naturally occurring range.

In the Australian Garden

In order to ensure that plants introduced into the Australian Garden do not create new environmental weeds in the RBG Cranbourne bushland or surrounding area, all plants proposed for use in the Australian Garden are subject to a weed evaluation process or model.

Each plant is assessed for its potential to invade the local bushland. Attributes such as the creation of copious seeds that readily germinate can mean that a plant has the potential to become a weed. Such plants are either excluded from the final planting or a management system is put in place to reduce its weediness, for example, by removing flowers before seeds develop and spread.

In the RBG Cranbourne bushland

Main woody weeds in the bushland

• Sweet Pittosporum – Pittosporum undulatum
• Sallow Wattle – Acacia longifolia
• Blue Bell Creeper – Billardiera heterophylla

Main grassy weeds in the bushland

• Sweet Vernal Grass – Anthoxanthum odoratum L.
• Veldt Grasses – Ehrharta spp.

The bushland at RBG Cranbourne is divided up into 36 management zones. During each three-year period the weeds within each zone are removed depending on their flowering periods. The control methods used are: hand weeding, cut and painting with herbicide, frilling (a technique where glyphosate is put into little cuts in the stem) and spraying. Care is taken to ensure that only the target weedy species are removed by these methods.

How do I find out about weedy plants in my area?

Most local councils are able to provide information on weedy plants in your area.

The City of Casey, Cardinia Shire Council and the City of Greater Dandenong have produced a Weed Identification Guide that is available from Council offices.

Frankston City Council has also produced a booklet on the Pest Plants of the Mornington Peninsula.