The wild ginger running rampant in Bastia Hill gullies has beautiful flowers but is among the 100 worst weeds in the world, Horizons pest plant management officer Neil Gallagher says.
He's back for another Wanganui weedbusting spring, and this time his target is wild ginger rather than woolly nightshade.
The ginger plants have scented yellow flowers from January to March.
"But don't let the good looks fool you. In actual fact it's a menace," he said.
Plants have spread out of gardens on Bastia and Durie hills into the wild, bushy gullies. Left alone, their rhizomes will form clumps up to a metre high. They will slowly creep outward, preventing other plants growing.
Birds will eat the 100 seeds on each flower stalk and spread them around to grow yet more plants.
Wild ginger is semitropical, and the warmth expected from climate change will speed its spread.
It can be controlled by spraying, cutting and spraying, or by manual removal. The best method depends on the situation and Mr Gallagher is willing to give advice or help.
He's got a team to work with, including the "Ginja Ninja", a ginger eradication specialist.
Horizons Regional Council has a prize - a 16-litre garden sprayer - for the person who finds the biggest infestation of wild ginger in Wanganui.
The ginger campaign will run until the end of November, and Mr Gallagher is happy to advise on other problem weeds as well.
He said his previous woolly nightshade campaigns had opened the eyes of people and got them talking.
"They're starting to think weeds, and that Horizons is there to help them."
Mr Gallagher can be contacted on freephone 0508 800 800.