Despite its long-lasting and eye-catching aromatic flowers, the lantana has spread over four million hectares in Australia, costing breeders more than $100 million a year.
Yet it’s far from the only ornamental plant species that conservationists say poses a risk to native ecosystems.
Australia is home to around 20,000 introduced plants, about the same number as there are natives, the vast majority of them being imported as ornamental plants for gardens.
While pampas grass and prickly pear vie with lantana as problematic invasive species, thousands of seemingly harmless species purchased from nurseries and markets can damage ecosystems if they “jump the fence” , says Michelle Leishman, a biologist at Macquarie University.
“Plants able to establish themselves in a new environment can escape from our gardens and spread into nearby bush where, conditions permitting, they can outcompete or smother our native vegetation,” she says.
Professor Leishman and his colleagues have designed a new location-based screening app to help gardeners and industry select plants that pose less risk.
Based on more than 30 years of testing and refinement, the Ornamental Plant Decision Support Tool checks alien species against some 24 criteria to determine their likelihood of becoming invasive.
It is a central part of Plant Sure, a new program launched by the Nursery and Gardening Industry Association of NSW and ACT, the Australian Institute of Horticulture and the NSW Government.
Still in trial mode, the project will feature a research portal that will evaluate exotic varieties and issue them with a responsible gardening certification sticker if they meet an endorsement.
Suppliers and sellers are, in turn, encouraged to choose plants that will reduce the risk of weed invasion.
The Plant Sure website also provides advice on what to do with particular ornamental plants, says Vicki Graham, conservation scientist at Macquarie.
The risk assessments involved are based on the best available scientific evidence to ensure rigor and credibility, she says.
“This will build confidence in the industry and in the community that the plants they choose, collect and recommend are not likely to harm our natural environment.
Australian Associated Press