This enormous water beetle is as rare as it is impressive.

A tall and hairy plant, Great willowherb displays pretty pink-and-cream flowers. It can be found in damp places, such as wet grasslands, ditches and riversides.

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.

The Welsh poppy is a plant of damp and shady places, roadsides and hillsides. It is also a garden escapee. It flowers over summer, attracting nectar-loving insects.

An uncommon tree of wet woodlands, riverbanks and heathlands, alder buckthorn displays pale green flowers in spring, and red berries that turn purple in autumn.

As its name suggests, Meadowsweet is a sweet-smelling flower of damp meadows, ditches and riverbanks. Look for frothy clusters of cream flowers on tall stems.

A delicate, small plant of woodlands and hedgerows, wood-sorrel has distinctive, trefoil leaves and white flowers with purple veins; both fold up at night.

A notoriously poisonous plant, hemlock produces umbrella-like clusters of white flowers in summer. It can be found in damp places, such as ditches, riverbanks and waste ground.

Look out for the small, yellow flowers of Celery-leaved buttercup in wet meadows and at the edges of ponds and ditches. It flowers from May to September.

Considered to be one of the prettiest gentians, the Chiltern gentian is a rare plant in the UK. It likes chalk grasslands, its purple, trumpet-shaped flowers blooming from August.

The early gentian is a rare plant that is only found in the UK. It likes sunny, lowland chalk grasslands, its purple, trumpet-shaped flowers blooming in May and June.