Despite its long-lasting, eye-catching aromatic blooms lantana has spread across four million hectares in Australia, costing graziers more than $100 million a year.
Yet it's far from the only ornamental plant species conservationists say poses a risk to native ecosystems.
Australia hosts an estimated 20,000 introduced plants or roughly the same number as there are natives, the vast majority of them imported as ornamentals for gardens.
While pampas grass and prickly pear rival lantana as problem invasives, thousands of seemingly harmless species bought from nurseries and markets can damage ecosystems if they 'jump the fence', says Macquarie University biologist Michelle Leishman.
"Plants able to establish in a new environment can escape from our gardens and spread into nearby bushland where, conditions permitting, they can out-compete or smother our native vegetation," she says.
Professor Leishman and her colleagues have designed a new locality-based screening application to help gardeners and industry select plants that pose less risk.
Based on more than 30 years of testing and improvement, the Ornamental Plant Decision Support Tool checks exotics against some 24 criteria to work out how likely they are to become invasive.
It's a core component of Plant Sure, a new scheme launched by the Nursery and Gardening Industry Association of NSW and ACT, Australian Institute of Horticulture and NSW government.
Still in trial mode, the project will feature a research portal which will assess exotic varieties and issue them with a Gardening Responsibly certification sticker if they meet a tick of approval.
Suppliers and sellers are, in turn, encouraged to choose plants that will reduce the risk of weed invasions.
The Plant Sure website also provides advice on what to do with particular ornamentals, says Macquarie conservation scientist Vicki Graham.
The risk assessments involved are based on best available scientific evidence to ensure rigour and credibility, she says.
"That's going to increase confidence in the in the industry and in the community that the plants they are choosing, collecting and recommending are not likely to cause harm to our natural environment.
Australian Associated Press
