Eradication is difficult. Killing the plant is a three- to five-year process that involves cutting them back at the peak of the bloom, when the plant is putting its energies into the flowers and the roots are correspondingly weakest. Mowing down the plants has proved more effective than herbicides.

Most of the culling is carried out by volunteers. Municipalities have been hesitant to allocate money, given the controversy surrounding the practice.

In the alpine town of Faskrudsfjord in East Iceland, Stefan Elvarsson, 18, was preparing to join a lupine slaughtering party. “When I was young,” he said, as if describing a long-lost way of life in the bustling harbor village, “we did not wade lupine fields to get up our mountain.”