A weed is simply a plant in the wrong place at the wrong time (and there are a lot of other definitions).

Environmental weeds are usually introduced species (often escapees from gardens) that have invaded natural environments and may form thickets and smother or crowd out native vegetation. Environmental weeds may include native species out of their normal range and therefore not subject to their normal biocontrol agents. Perhaps the only unifying feature of weeds is that they tend to reproduce prolifically (usually by seed). The seed may remain viable for a long time and can be spread widely by wind, water or birds. Weed populations can be slow to build up and are not noticed until they have become a significant problem.

Schinus terebinthifolius

Not surprisingly weeds differ in their seriousness and there are various schemes for categorising them (all of which are somewhat arbitrary). Some weeds are merely a nuisance while others are declared in legislation and must be controlled. Some are declared Weeds of National Significance. The status of a weed may depend on the local government area.

Fraxinus grifithii

How many weeds are there? Obviously this depends on the location and the situation (particularly given the definition of a weed). The publication Weeds of Central and Northern Queensland (2019) lists 162 weeds (36 woody weeds, 18 succulents, 24 vines, 42 herbs, 24 grasses, 6 sedges, 12 aquatics). The publication Weeds of Mackay and the Whitsundays (2013) lists 264 weed species (5 palms, 36 trees and shrubs, 35 sub-shrubs, 99 herbaceous broad leaf, 32 grasses, 6 cacti, 37 vines, 4 aquatics). These numbers emphasise the arbitrary nature of defining weeds.

lantana camara

You can do your bit to protect the natural environment and improve biodiversity:

a) Use native plants by preference in your gardens (rather than introduced species)

b) If using introduced species take precautions to stop their spread (don’t dump waste)

c) Learn to recognize weed species (particularly environmental weeds)

d) Remove weeds when you see them e) consider volunteering for one of the local ‘weed wacker’/’weed warrior’ work groups


Bob Newby [NOV 2022]