A plant known as "Cook's scurvy grass", which Captain James Cook fed to his sailors to ward off the fatal disease, has been found growing on a tiny island off Waikato, having been previously thought almost extinct.
The British explorer made great efforts to keep his crews in good health and to ward off scurvy, caused by vitamin C deficiency.
He gave them vinegar and sauerkraut, and while charting the coast of New Zealand in 1769, harvested the grassy plant, known as "nau" by Maori.
The grass, a type of cress, proved a valuable food source.
But in recent times it was thought to have almost died out, found only in a handful of small colonies on the west coast of the North Island.
Twenty-five years ago, ecologists had a hunch that a site near Albatross Point, south of Kawhia harbour, was a likely site for the species.
But although it was only 150m off shore, it was inaccessible from the mainland except by helicopter because of dangerous currents and sharks.
Last week a Department of Conservation team landed on the islet, courtesy of a helicopter belonging to New Zealand Steel, which was working in the region.
It found more than 80 plants, growing in an area half the size of a rugby field.
The team leader, plant ecologist Andrea Brandon, said that only two of the mainland sites contained more than 20 plants.
"This is a very significant find for the region, and indeed for the whole of the North Island, where this species is now seriously at risk of going extinct," she said.
She and her two colleagues found the grass - Lepidium oleraceum - growing under tree cover.
Dr Brandon said Cook had recognised the value of the plant, which grows to a height of about a metre. "It was recorded as abundant back then," she said.
Cook came across it when he visited New Zealand for the first time, during his first great voyage of exploration. He harvested it again when he returned here.
Scurvy was a scourge of the British Royal Navy, because it was impossible to store fresh fruit and vegetables for the duration of long voyages, which led to sailors falling ill with vitamin C deficiency.
In the late 18th century lime juice was discovered to be effective in preventing the disease.
The Navy began distributing regular rations, which led to the nickname "limey" for British sailors.