A weed is simply a plant out of place growing where it is not wanted. However, weeds are not simply a problem confined to home gardens. Weeds have a major impact on agricultural productivity and the environment and to a lesser extent on human health. It is estimated that weeds cost Australia in excess of $4 billion annually. The high adaptability of weeds to access light, moisture and nutrients within new environments gives them a competitive edge over local indigenous flora and other desirable plant species.

Over 27,000 known alien plant species have been introduced to Australia. Around 2,800 of these plants are now established as weeds in the Australian environment with around 1,800 (66%) being introduced originally as horticultural plants. This means two thirds of the weed species causing measurable negative impact within the Australian environment are escaped garden plants with invasive ability. The number of naturalized weed species within Australia is rising by about 10 species per year, and the rate is increasing.

Two major weed groups often referred to in weed management and which have particular relevance within the Woollahra Local Government Area (LGA) are Environmental Weeds and Noxious Weeds.

Useful websites

• Weed Identification and Information (Australian Weeds Committee)
• Weed identification resources (NSW Dept. of Environment and Climate Change)
• Identifying weeds (Australian Government)
• Weed information (Weed Information)
• Information about individual weed species (CRC Weed Management)