In the New Forest in England, P. longifolia shares its habitat with wild daffodil (Narcissus pseudonarcissus), bluebell (Hyacinthoides non-scripta), wood-sorrel (Oxalis acetosella), bastard balm (Melittis melissophyllum), wood anemone (Anemone nemorosa), columbine (Aquilegia vulgaris).
Melittis melissophyllum is a species of flowering plant in the mint family, Lamiaceae.