In the horticulture world, there’s one word that can strike fear into the hearts of many: weeds.
Weeds are one of the most misunderstood parts of our landscapes. While many folks automatically associate weeds with invasive plants taking over gardens or bushland, not all of them are bad – and not all of them look like trouble at first glance.
In Queensland, weeds come in many forms – but how can you tell the difference between the harmful and the helpful? And what should you do if you spot a problem plant in your backyard?
We’re here to give you the lowdown on this divisive type of plant life, including how weeds are classified, the most common weeds in Queensland, and how you can get rid of any pesky plant-based intruders.
What are weeds?
A weed is simply a plant growing where it’s not wanted – but there’s more to it than that. A plant may be considered a weed if it spreads aggressively, disrupts natural ecosystems, or causes problems for agriculture, waterways, infrastructure, or human health. In Queensland, the highest-risk weeds are regulated under the Biosecurity Act 2014.
Weeds can be introduced species brought in from overseas or interstate, often intentionally introduced for agriculture, horticulture, or as garden ornamentals. Others might be native to parts of Australia but behave like weeds when they grow outside their natural range.
Many weeds grow quickly, produce lots of seeds, and have effective dispersal mechanisms, making them difficult to control once established. That’s why early identification and management are key to stopping their spread.
Don’t let the pretty flowers fool you – some weeds like the blue morning glory (Ipomoea indica) here can spread rapidly and smother natives.
How do weeds impact the environment?
Weeds can have serious impacts on the environment. By outcompeting native plants for sunlight, water, and nutrients, weeds can quickly take over natural areas, reducing biodiversity and altering entire ecosystems. Some weeds form dense monocultures, which crowd out native species and change how water flows through the landscape, how fire behaves, and even how animals use the habitat.
In fragile or threatened ecosystems, the spread of invasive weeds can push already vulnerable species closer to extinction. They can also disrupt food webs by replacing native plants that local wildlife depend on for food and shelter. Aquatic weeds can clog waterways, reduce oxygen levels in the water, and smother fish and aquatic life.
It’s not just wild places that are affected – weeds can also damage farmland, reduce crop yields, and increase land management costs for farmers, councils, and property owners.
What are some common weeds in Queensland?
We’ve listed some of Queensland’s most common weeds to keep an eye out for:
Harmful and invasive weeds
These species are listed under the Biosecurity Act 2014 in Queensland due to their ability to spread rapidly and cause serious harm. We’ve popped in the category of each species for quick reference so you can see what level of threat they pose. It’s worth noting that Category 3 weeds don’t need to be reported – however, you must not release these invasive plants into the environment, give away, or sell as a plant or something infested with its seeds.
Lantana (Lantana camara)
Category 3: Restricted
Colourful but highly invasive, lantana forms dense thickets that smother native vegetation and can be toxic to livestock.
Parthenium (Parthenium hysterophorus)
Category 3: Restricted
A fast-spreading weed that causes allergic reactions in humans, reduces pasture productivity, and displaces native grasses.
Prickly pear (Opuntia spp.)
Category 3: Restricted
Once a major pest in Queensland, prickly pears are still a problem in some areas, forming dense, impenetrable thickets.
Hymenachne (Hymenachne amplexicaulis)
Category 3: Restricted
An aquatic grass that clogs wetlands and displaces native water plants.
Mother-of-millions (Bryophyllum spp.)
Category 3: Restricted
A succulent weed toxic to cattle and extremely difficult to remove once established.
Siam weed (Chromolaena odorata)
Category 3: Restricted
A highly invasive shrub found in northern Queensland that can overtake pastures and bushland.
Giant rat’s tail grass (Sporobolus spp.)
Category 3: Restricted
A tough, unpalatable grass that reduces the quality of grazing land and is very difficult to control.
Garden escapees that become weeds
Some plants were introduced as ornamentals but have since become weedy in the wild.
Singapore daisy (Sphagneticola trilobata)
Category 3: Restricted
A groundcover that spreads rapidly, smothering native ground flora along creeks and roadsides.
Cat’s claw creeper (Dolichandra unguis-cati)
Category 3: Restricted
A climbing vine with yellow flowers that strangles trees and causes canopy collapse in bushland.
Green cestrum (Cestrum parqui)
Category: Not a prohibited or restricted invasive plant under the Biosecurity Act 2014.
A poisonous shrub that is toxic to livestock and wildlife.
Common nuisance weeds in backyards and lawns
These might not be declared weeds, but they’re unwelcome in many gardens and can be hard to control.
Cobblers pegs (Bidens pilosa)
Photo credit: Brisbane City Council
Category: Not a prohibited or restricted invasive plant under the Biosecurity Act 2014.
Recognisable by its sticky black seeds that attach to clothes and fur. Thrives in disturbed soils.
Nutgrass (Cyperus rotundus)
Photo credit: Brisbane City Council
Category: Not a prohibited or restricted invasive plant under the Biosecurity Act 2014.
A stubborn lawn and garden weed that spreads via underground tubers.
Bindii (Soliva sessilis)
Category: Not a prohibited or restricted invasive plant under the Biosecurity Act 2014.
The infamous lawn weed that produces painful prickles in summer.
How to identify harmful weeds in your yard
Need to decipher whether a plant in your backyard is a friend or foe? The folks at the Queensland Herbarium have kindly collated a mega-list of resources to help you identify different kinds of weeds. Apps like iNaturalist allow you to get crowd-sourced identifications from other users around Australia (and the world), while others like Weeds Australia help you search a huge database by checking off specific features that match the weed you’re looking for.
We’ve looked at some common weeds, but we know that prevention is better than the cure! Some weeds are highly likely to cause significant impacts to the environment, agriculture, the economy, and our way of life. Keeping new high-risk weed species out of Queensland and detecting new incursions early is the most effective way to reduce their impact.
The species assessed as being the highest risk and that are not known to be in Queensland are listed as Prohibited under Queensland’s Biosecurity Act 2014. If you want to help protect Queensland from new high-risk weeds, look into joining the Weed Spotters Network – it’s a fantastic citizen science program that aims to detect new and emerging weed threats, with a particular focus on species listed as Prohibited or Restricted (Category 2,3,4,5) under the Biosecurity Act 2014. You can join more than 1900 other Queenslanders keeping an eye out for and reporting high-risk species during their regular activities.
How to control weeds on your property
Controlling the spread of weeds in Queensland is in everyone’s best interests. If you’ve got some problematic plants running riot in your backyard, there are a couple of methods you can use to either eradicate or control them. The Queensland Government has loads of information about how to control specific weeds using either herbicides or physical control methods (like hand pulling).
Basically, different weeds will respond better to specific methods. The weed identification resources we mentioned above often have management and eradication advice attached to each particular species, so you can be sure you’re attacking the problem most effectively.
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