Wingspan 7-11.5 mm.
The larvae of this widely distributed species feed within the seedpods of broad-leaved willowherb (Epilobium montanum), and occasionally on other willowherb species. The affected pods may be recognised as they become thickened, shortened, distorted and often redden prematurely. The pod will also have a hole in the side.
The adults emerge in late summer and may be seen on the wing any time until late spring. They may often be found overwintering inside garden sheds etc. The moth is common in England and Wales, with a restricted distribution in Scotland and Ireland.