Imported flower posing $5 billion threat to Australia: 'Massive problems'

Yahoo

2 days ago

Invasive species experts are sounding the alarm over a nasty weed continuing to sting the Australian economy, that outcompetes native vegetation, is extremely difficult to remove and is even still being sold at nurseries.
The South African native flower gazania has proven far more adaptable than once believed, emerging as a serious invasive threat to Australia's native grasslands and grain-growing regions, a recent La Trobe University study has found.
Dr Ali Bajwa's Weed Science group at La Trobe Institute for Sustainable Agriculture and Food (LISAF) collected thousands of seeds from environments across the country and studied how they grew under various conditions.
He spoke to Yahoo News and said that what makes the gazania problem particularly urgent is the fact it has very few weaknesses. Invasive plants like gazania are already a major burden on Australian agriculture, contributing to over $5 billion in losses each year.
Although popular as a drought-tolerant ornamental plant, gazania is highly invasive and thrives in disturbed soils and coastal habitats, where it spreads quickly by seeds. This aggressive growth allows it to outcompete native groundcovers and wildflowers, leading to a loss of native plant diversity.
The dense mats it forms also alter soil composition and prevent the regeneration of indigenous species. Additionally, it provides limited habitat or food value for native insects and animals, further disrupting local ecosystems.
Gazania, also known as treasure flowers, has now spread extensively across South Australia and parts of Western Australia, and it can be found colonising everything from coastal dunes and creek banks to wastelands, open grasslands, roadsides, and even cultivated and irrigated farmland.
"We know they are quite widespread, but what we wanted to understand was if there are certain climatic conditions or soil types that are more favourable to gazanias compared to others," Bajwa said.
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"And what we found is it has quite flexible germination potential across different temperatures, soil types, moisture gradients, and there aren't many limiting factors, unfortunately, in terms of its early establishment and germination.
"One of the things we noticed was that if you bury them beyond a certain depth, they can't emerge from those deeper soil layers. Other than that, unfortunately, there aren't many weaknesses to exploit."
Although gazania has long been recognised as an environmental weed, it has recently begun to invade grain cropping zones in South Australia's lower rainfall areas. Farmers are now struggling to manage its spread, as standard herbicides are proving largely ineffective.
Initially introduced to Australia in the 1950s and '70s as a decorative garden plant, two varieties of gazania made their way here through discarded garden waste, including lawn clippings, seeds, and other plant material, enabling them to establish along roadsides and to take over native ecosystems.
In regions with sandy, marginal soils, gazania infestations are rendering the land unproductive. Its hardy, drought-tolerant nature allows it to outcompete young crops, leading to widespread agricultural losses.
"They've now started jumping the fence and getting into those really high-value conservation areas, but also into grain production systems, where they're causing massive problems and yield losses — and revenue losses in terms of the money spent to manage them," Bajwa said.
"Restricting the sale and also declaring them a weed of some importance would go a long way — because then it all of a sudden raises more awareness among the public, and also gives weed management authorities a bit more focus to manage this.
"We have a lot of other invasive species, and resources are quite limited, so further legislation on restricting their sale, propagation and planting would help. But we also need funding to do some of the research — the sort of work we're doing — to actually get ahead of the invasion curve and try to figure out what the potential management strategies could be.
Bajwa encouraged the public to be aware of its dangers and the negative impacts the species can have. "Further planting, propagation and dispersal should also be discouraged," he said.
The study, led by PhD student Muhammad Adnan from Dr Bajwa's Weed Science group at the La Trobe Institute for Sustainable Agriculture and Food (LISAF) and the Department of Ecological, Plant and Animal Sciences, was published in Frontiers in Agronomy.
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