Recent rain after a dry summer has seen Paterson's curse flourish this winter in the ACT, but authorities are also concerned about less eye-catching and potentially more destructive weeds such as Chilean needle grass spreading in the territory.
Patches of the distinctive purple weed, also known as salvation Jane and Riverina bluebell, have sprung up in paddocks and reserves across the ACT, including on Mount Taylor.
Invasive plants project ranger Harley Baker, from the ACT Parks and Conservation Service, said good winter rain had caused the noxious weed to proliferate.
One Paterson's curse plant could produce 5000 seeds in a year and the seeds were able to remain dormant in the soil for up to five years, waiting for a downpour.
"Also, coming out of a prolonged dry period, there would have been some extra grazing pressure on some of the perennial grasses which would usually suppress Paterson's curse," he said.
"So the dry period and grazing leads to a little bit more bare ground which leaves it ripe to be invaded by something like Paterson's curse."
Paterson's curse is toxic to livestock, especially horses. Biological controls such as the Crown weevil were not in big numbers.
ACT government rangers and contractors were spraying Paterson's curse, prioritising areas where it might be encroaching on wildflower sites.
Last financial year, 183 sites were sprayed for Paterson's curse, covering 100 hectares. Already this financial year, 35 sites had been sprayed across 52 hectares.
"So, we've treated more than half of last year's area in the first two months of the financial year," Mr Baker said.
ParkCare volunteers also manually removed Paterson's Curse from Canberra Nature Park reserves.
But Mr Baker said the government had to prioritise weed removal based on threat and other weeds such as Chilean needle grass, which might not be as eye-catching, were more destructive and needed more immediate attention.
A map of the ACT government's invasive plant control program can be found here.
