The kahukura, is endemic to New Zealand and it turns out the nettle spines (yes the stingy kind) are absolutely essential for these butterflies to propagate their caterpillars on.
Because of its nasty sting, the native nettle and other introduced species have been heavily sprayed over the years. This has seen the nitrogen soil loving plants dwindle substantially in both the countryside and around gardens. As it has disappeared, so have the native red and yellow admiral butterflies that lay their eggs on them.
Other than the countless medicinal uses for the glorious nettle here’s just one other reason to keep a pot of nettles in the garden.