The number of native plants under threat is being partly blamed on conversion of sheep farms to dairy operations.
A study has found that six species of native plant are now regarded as extinct and the number of plants under threat has jumped almost 50% to 180.
Department of Conservation scientist Peter de Lange says a change from sheep to dairy farming is having a significant effect on land, particularly in the drier eastern parts of the South Island. He says it is draining wetlands and starving plants.
But Federated Farmers questions how much land the department needs to protect plants, noting that a considerable amount is already under the department's control.
Conservation body Forest & Bird says an increase in vineyard numbers is also putting pressure on native plant life.