Invasive weeds are a serious threat to biodiversity in Victoria both on land and in aquatic environments.

Weeds compete with native plants for space, nutrients and sunlight. They change the natural diversity and balance of ecological communities. Weeds also affect the function native species have in providing nutrients and habitat for other species.

Weeds that have been introduced into the Australian environment have no natural controls from insects, grazing animals or fungi that feed on them to limit their spread.

There are over 1000 species of weeds occurring on public land in Victoria. A comprehensive list of weeds is available on the Department of Primary Industries website.

More about weeds

• Weeds often reproduce in a way that allows them to spread over large distances. For example, willows have winged seeds that are carried on the wind tens of kilometers from their source
• Woody weeds, such as blackberry and gorse, shade out native plants and create impenetrable thickets
• Scrambling weeds such as Bridal Creeper, smother native plants and create dense root mats that prevent other plants from accessing adequate moisture and nutrients
• Some exotic grasses out-compete native grasses and can create high fuel loads that can cause greater bushfire intensity
• Some weeds, like the Hawkweed, can produce biochemicals that inhibit the growth of other plants around them

• Marine weeds can release large amounts of spores allowing them to reproduce quickly.

Management

Parks Victoria works with the Department of Primary Industries, other land managers, land owners and community groups to manage weeds in parks.

The four objectives for weed management are to:

• Prevent their spread by making sure equipment and vehicles are clean of seeds and spores
• Eradicate small infestations that are unlikely to have spread beyond a definable boundary
• Contain infestations where they can be prevented from expanding beyond a defined containment line
• Protect assets (e.g. native plants and animals, neighbouring agricultural land) from the impacts of invasive weeds by reducing population densities.

Weed infestations are controlled mainly through the use of chemical sprays. However, in fragile environments such as the alpine peatlands and marine environments, weeds may be pulled manually by hand.

Biological control is another way weeds are controlled. This is when one living species (such as a plant, fungi or insect) is introduced to control an unwanted species. Biological control may be used when weeds are too widespread for chemicals to be used.

Related links

• Department of Primary Industries
• Department of Sustainability and Environment
• Department of Sustainability and Environment - Marine pests