Holidaymakers are being recruited to help in the fight against foreign invaders.
The Department of Conservation (DOC) is asking those holidaying around the country to look out for various introduced species of weeds that are destroying native plants and altering landscapes.
A DOC ranger, Evan Shaw, said the organisation controls up to 350 different species of weeds, but is asking people to look out for 13 types, which he dubs the Dirty Dozen.
"This is our baker's dozen, we are highlighting 13 of the more visible weeds that can be seen as you drive around the country, we want to highlight the effect that weeds are having on the country," he said.
"What we define as a weed is a plant that is growing in the wrong place. New Zealand has around 2000 native species of plant. We've also got about 20,000 introduced species, these are other plant species that are bought in from all around the world.
"Around 2000 of those are going to naturalise and be able to reproduce in the wild by themselves, and around 200 of those are going to become fully invasive species. Those are ones that can grow in the wild by themselves and then start altering the environment around them, and those that we determine as invasive weeds."
Mr Shaw said DOC was encouraging people who spotted the weeds to take photos of them and log the information about where they were found on the website Naturewatch.org.nz, which also has an app.
That information will help build a national database about where the weeds are most prevalent, which could then be used by various organisations interested in biosecurity or the environment, he said.
"People can record observations of species that they see around the place, so if you spot one of our Dirty Dozen record the sighting, and what that does is that helps build a picture of where we can find these things."
Mr Shaw said DOC was doing a lot of work to tackle the war on weeds, and it was proving successful.
"But there is an awful lot of the country that we simply can't get to, to weed, that's why we want to enlist the help of communities so they can know what the weeds are, so they can start doing work in own back yards and ripping out the plant if they see it."