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Land managers across The Hawkesbury have long grappled with weeds in a constantly shifting environment, changing climate, unpredictable weather patterns and evolving landscapes all create opportunities for new invasive plants to emerge. Some are manageable; others become costly, stubborn problems that threaten farms, bushland and biodiversity.
Here in the Hawkesbury, our diverse environments, the mountains, river flats, subtropical forests and open woodlands provide countless niches for unwanted plants to take hold. Blackberry, privet and thistle are well-known examples. But today, a growing trend toward exotic and unusual garden plants is creating new weed risks. For better or worse, our own gardens are becoming launch pads for species that escape into the wild and compromise the stability of this ancient landscape we call home. Climate change adds another layer, allowing plants once considered benign to thrive and spread in ways not previously seen.
Retail Sales of High-Risk Plants Under Scrutiny
The Gazette recently reported on Gazania rigens, a noxious small flowering annual found for sale at Bunnings McGraths Hill and likely at many other outlets nationwide. As the ABC has also reported, gazania has already spread into paddocks in parts of Australia, making some farmland unviable and prompting calls from farmers, environmental groups and researchers for national regulation to ban its sale. Its clear consumers cannot be expected to identify high-risk species when retailers continue to offer them without warnings. One simple safeguard for the average gardener: choose native plants, which are far less likely to become environmental threats.
Local Action: Western Sydney Weeds Authority Steps Up
To understand how the Hawkesbury is responding to these emerging threats, the Gazette spoke with Chris Dewhust, General Manager of Hawkesbury River County Council, soon to be renamed the Western Sydney Weeds Authority.
Chris and his team are acutely aware of the escalating risks and have positioned the organisation to better inform and support landowners facing weed infestations. They are currently compiling a list of qualified, knowledgeable and insured contractors who can assist private landowners with weed control across the region. Once finalised, the list will be published on the Authority’s website.
For now, the Hawkesbury River County Council site remains a key point of
reference: www.hrcc.nsw.gov.au
A History of Introductions And Escapes
Garden escapes are not new. The humble ox-eye daisy, for example, currently a problem in several highland paddocks within the Hawkesbury emerging post the 2019 bushfires was deliberately introduced as a garden ornamental in the 1850s, first cultivated at the Adelaide Botanic Gardens in 1858. By the late 1800s it had broken free, becoming naturalised across parts of Victoria, South Australia and Tasmania after spreading through garden waste and unmanaged cultivation.
But experts warn the scale of today’s problem far exceeds anything from the past.
Imogen Ebsworth, national strategy lead at the Invasive Species Council (ISC), said "the ecological damage already caused by escaped garden weeds such as gazania is small compared to the potential threat posed by the tens of thousands of plant species currently offered for sale".
“We know there are more than 30,000 different plant species available for sale for your garden in Australia, and the vast majority haven’t been assessed for whether they’re going to turn into a major weed,” Ms Ebsworth said. "We’re in a situation of terrifying known unknowns. We’ve introduced so many plants into Australia that when you walk in your local bush, one in eight of the plant species you see are introduced.”
In the past year alone, the ISC has found numerous high-risk species still being sold in nurseries, including mock orange (Murraya paniculata), duranta (Duranta erecta), mother-in-law’s tongue (Sansevieria trifasciata), Japanese honeysuckle (Lonicera japonica) and English ivy (Hedera helix). Even among legally permitted plants, at least 5,000 are known weeds overseas.
A Costly National Burden
The Australian Centre for Invasive Species Solutions estimates noxious weeds cost Australia around $5 billion every year, accounting for agricultural losses, environmental harm and the expense of trying to control them.
Carol Booth, policy director at the Invasive Species Council, captures the scale of the crisis: “Weed management is Australia’s most expensive land management problem for both the environment and agriculture.”
A Local Challenge with a Local Solution
As exotic plants continue to arrive in nurseries faster than they can be assessed, and climate change broadens the conditions in which they can thrive, the Hawkesbury faces increasing pressure to stay ahead of fast-moving weed threats.
But with strengthened local coordination, the work of the Western Sydney Weeds
Authority, and an informed community of landowners and gardeners, the region is better positioned than ever to protect its landscapes.
And one message is clear: what we plant today shapes the environment our children inherit tommorow.
