Amethyst (H1) flowers, barrel-shaped, VIII–IX; dark green foliage; strong, upright habit; height 31–45cm; spread 46–60cm.
Wild-collected; found at Lough Nacung, County Donegal, Ireland, by Dr E. C. Nelson (National Botanic Gardens, Glasnevin, Dublin, Ireland) in 1978.
Named from Errigal, the mountain at the foot of which Lough Nacung is situated; dusk was chosen because of the dusky purple colour of the corolla.
