It is is most noticeable in October and November, when it flowers.
It has been impossible to eradicate in New Zealand since it arrived in the 1960s. In the Horizons region, it is authorised for removal in certain places only.
This season, Horizons contractors will remove it from lakes Pauri and Wiritoa, high-priority wetlands. Mr Gallagher advised anyone who did not want it in their vicinity to simply pull it out.
Pink ragwort originated in South Africa. Its seeds are tiny and can travel at least 6km in the wind. It spread up the coast from Wellington, reaching Wanganui in the 1990s and Taranaki in the 2000s.
Since 2010, populations had "exploded", Mr Gallagher said.
But pink ragwort is not going to take over the world, because it spreads madly only in warm coastal places with a reasonable rainfall.
The plants can grow to 1.5m tall and live four or five years. They are no threat to inland New Zealand or the South Island, which is too cold.
Stock eat young plants, so they are not a threat to pasture, and they do not grow in native forests.
However, Conservation Department staff and volunteers have spent untold hours pulling them out at Whitiau Scientific Reserve, on the Wanganui coast.
And the Taranaki Regional Council is fighting to keep them south of Mt Taranaki.
"If it gets past Mt Taranaki, it could get all the way to Northland. It would go crazy up there, because it's a very suitable habitat," Mr Gallagher said.
