Weeds and Seeds — and You!

Scott Heiman — 5 November 2020
Australia has it all when it comes to landscapes. But are we killing it slowly with our dirty caravans and tow tugs?

Be honest, when was the last time you washed your caravan and tow tug's underbelly? Was it when you got home from your last trip away? Was it even longer? If so, your rig is probably carrying weeds and seeds that could endanger the very environments we take such efforts to visit.

Weeds and seeds are a real problem. They threaten our biodiversity, landscape and water resources, and cost our agricultural industries in excess of $4 billion annually nationwide. That’s the equivalent of building 1000 new primary schools, 400 district hospitals or 1500 new nursing homes every year. What’s more, you can be sure this cost is reflected in the price of steak, beer and pizza at home and on the road.

When it comes to biosecurity it isn’t simply something that happens at Customs checkpoints at airports. It’s something that affects us daily — or more accurately, we affect it.


Bioregions are technically known as geophysical patterns with groupings of fauna, flora and processes that operate at an ecosystem scale. More colloquially, bioregions are simply the special places where parts of our environment interact and have dependencies on each other in ways that don’t happen anywhere else on the planet. 

Chances are we’d all recognise a unique bioregion when we travel from our world-renowned beaches to muddy mangroves, snowy mountains, tropical rainforests and dry deserts. It’s these bioregions that make Australia such a drawcard to travellers. But unique bioregions can be less obvious too. The Kimberley is ‘just’ the Kimberley right? Actually, it has five separate bioregions, including rugged ranges, dramatic gorges, towering limestone cliffs, semi-arid savanna and isolated coastline. 

Our bioregions can be delicate and hard to notice. Consider, for example, a Eucalyptus forest. Picture differences in the 700 different species. Then consider the fact koalas from one region will eat a different species from those in another. It’s why you can’t rescue a koala from one place and have it relocated to a random location. 

Australia has 89 separate bioregions and 419 subregions, some with subtle changes that are no less important because of that fact. This means we can easily pass through several unique bioregions in just a few hours on the road. While this can be great for tourism, it’s not so great for the bioregions themselves.

While many people call to ‘unlock’ as much of our natural environment to the public as possible, in some places there may be good reasons to keep our distance. Australia’s obligations under the Convention of Biological Diversity require that 17 per cent of our continent is to be protected as part of the National Reserve System. In reaching this target, priority is given to under-represented bioregions that have less than 10 per cent of their remaining area protected in reserves, which isn’t a whole lot of land of when you consider the potential benefits to our — and future — generations.


Traditionally, plant seeds were spread by the wind, got caught in animal fur, were consumed by birds, or floated down our waterways. When they were deposited on suitable ground, they simply sprouted, and our environment developed in its own natural way. 

Once humans, particularly Europeans, arrived, however, the process of alteration to bioregions accelerated at a rate that endemic species simply couldn’t adapt to. And it’s not just the foxes, cats, rats, horses and cane toads that are causing an issue. 

Since 1788, we’ve lost 25 per cent of our rainforest, 45 per cent of open forest, 32 per cent of woodland forest and 30 per cent of mallee forest across Australia. In NSW alone, more than 100 species have gone extinct in the last 200 years. In their place, we’ve introduced species which have thrived so well they’re now considered weeds.

Weeds are any unwanted plant that out-competes more desirable plants. They usually produce large numbers of seeds, are often excellent at surviving and reproducing in disturbed environments and can usually flourish in a variety of conditions. 


We contribute to this country’s weed problem every time we hit the roads, travelling through farm land, arid outback, rainforests, national parks, and old mate’s secret place. In doing so, we cross creeks, pull over onto verges, and set up camp miles from where we started our journey. Inevitably, we end up with seeds under our floor mats, dirt in our chassis rails and mud on our tyres. 

There are many other sources of contamination too. Think of the burrs and seeds that get caught in the fur of our four-legged travel buddies. Or how about our tent pegs? The soil they collect can carry weed seeds and soil-born parasites. And, we all know that our shoes are a magnet for seeds as we walk. 

Every time this happens, we unwittingly spread plant material from the place that it came from, to a place where it doesn’t belong. Consider the strange weeds growing in your front yard. Maybe they’re from the crud you washed off your rig when you got back from the back of Bourke? 


Transporting weeds can damage the environment, and it can also hurt our hip-pocket because there are hefty fines in all states and territories for failing to ensure our vehicles are free from reproductive material of declared pests. 

In Queensland, for example, the penalty is up to $20,000. In the Northern Territory, you might be looking at a $200 on the spot fine, or between $5,000 and $50,000 if you end up in court. Penalties for businesses are even higher. Beyond fines, there are other controls against biohazards, too. Believe it or not, you can be kicked out of your favourite winery’s carpark if they think your rig could risk their crop.

It’s for reasons like these we find truck washes in far-flung places like Charleville. Livestock trucks moving south have to stop and wash the ‘moo poo’ off the floor to get rid of any seeds or parasites that might be present in the animal faeces or their muddy hooves. There are places like this near every state border. 

The same applies to your 17ft-long ‘home away from home’.


When washing your rig, it’s not about making it prettier than the next one. It’s about making it as clean as new! There’s an old adage in the contaminated machinery arena that says, ‘if you’re not as wet as your rig when finished, you’re not finished.’

So, to have properly washed down both trailer and tow-tug, you need to have washed out the dust, mud and debris from your chassis, bash plates, and the grass that’s been caught on your undercarriage. The same applies to the clay caught on the inside of your tyre rim. While it’s disturbing your wheel balance it’s also putting the environment at risk. 

Get it right or the dust, parasites and plant material that has accumulated in the nooks and crannies of your rig’s nether world over the last 4000km will become a farmer or ranger’s nightmare for the next 10 years. 


The bushfires of last summer have opened the door to accelerated weed infestation, as these scarred landscapes create the sorts of conditions in which weeds thrive, denying the opportunity for native regeneration to slowly occur. 

So before you hit the roads to help out communities recovering from bushfire, take the time to wash your rig. While your tourism or BlazeAid will help get people back on their feet, your seedy hitchhikers will do nothing but damage.


Weeds of National Significance (WoNS) is a list of 32 plant species considered the most problematic in Australia. Both state and federal governments have agreed (that’s a first) that these weeds, based on their invasiveness, and potential for spread and environmental, social and economic impacts, are a biosecurity threat to our nation.


If you’re travelling through the NSW Riverina or Lachlan and Macquarie valley regions, you might notice some of the road side guide posts are red, not white.

Just like most ‘red things’ in nature, they mean ‘danger’. In this case, they’re a signal that the verge is infested with a known weed and that it’s illegal to pull over into those areas.

If you’re alert, you’ll notice that the first sign says start and the next one says end. This signifies the total area of infection. In some council areas, they also have the name of the weed on the post, but if you get close enough to read it, you’re probably already too close!


When cleaning your rig, pay attention to the inside as well as the outside, by using a brush or vacuum on the foot wells, dashboard and seats — after all it’s not just gold coins that fall between the cracks. 

We love our 12–18V blower vac for this task. It helps dislodge seeds, pollen and dust from the radiator, engine bay and caravan. When the cleaning’s done, it’s also handy for putting life back into the campfire after we’ve finished with the coals from camp oven cooking!


Feature Biosecurity Tips and tricks Around Australia Weeds Pests


Scott Heiman