Look for the deep magenta, star-shaped flowers of Marsh cinquefoil in marshes, bogs, fens and wetlands in the north, west and east of the UK.

A climbing plant of hedgerows and woodlands, Black bryony produces greenish flowers in summer and red, shiny berries in autumn. It is a poisonous plant.

The Marsh helleborine is a beautiful orchid of fens, wet grassland and dune slacks. Growing in profusion in places, look for reddish stems and white-and-pink flowers.

Europe's largest frog is not naturally found in the UK, but was introduced to Kent and has spread throughout the southeast.

The bright blue, trumpet-shaped flowers of the marsh gentian contrast deeply with the pinks and purples of the wet heaths it inhabits. The New Forest holds a large population of this late-…