Calystegia silvatica can be distinguished from the very similar calystegia sepium by its epicalyx bracts, which are overlapping and curved around the calyx, rather than flat and non-overlapping.
Main flower color:
Most areas of the British Isles, though commonest in central/south England and Wales. A naturalised species
A creeper, with stems up to 4 m long
Verges, disturbed ground, beach margins
White, funnel-shaped, up to 7 cm across; pentagonal when viewed from above. At the base of the corolla is a green, five-lobed calyx that is largely or completely hidden by two overlapping epicalyx bracts
Alternate, oblong to arrow-shaped, up to 12 cm long
June to September