The Common walnut tree produces a large, brown nut that is familiar to so many of us. It is an introduced species in the UK, and can be seen in towns, gardens and parks.

Eyebright has small, white flowers with purple veins and yellow centres. It likes short grasslands, from clifftops to heaths, and is one of a number of species and hybrids that are hard to tell…

Fat hen is a persistent 'weed' of fields and gardens, verges and hedgerows. But, like many of our weed species, it is a good food source for birds and insects.

Freshwater pearl mussels spend their adult lives anchored to the river bed, filtering water through their gills and improving the quality of the water for other species.

The Migrant hawker is not a particularly aggressive species, and may be seen feeding in large groups. It flies late into autumn and can be seen in gardens, grasslands and woodlands.

Ivy-leaved toadflax is an introduced species in the UK that has become widely naturalised. Look for creeping along old walls and pavements, and shingle beaches. Its flowers resemble those of…

The turtle dove is the UK's fastest declining bird species and is on the brink of extinction. A small and pretty pigeon, it breeds in lowland England and winters in Sub-Saharan Africa.

A tall and robust species of sedge, the Great fen-sedge has long leaves with sawtooth edges. It forms dense stands in lowland fens and around lakes.

One of the most colourful fish in UK seas, the cuckoo wrasse looks like it belongs in the tropics. Don't be fooled though, it's very much a native species.

The White-clawed crayfish is a freshwater, bronze-coloured crustacean with pale undersides to its claws - hence the name. It is under threat from an invasive and introduced species of crayfish.…