Ground-elder was likely introduced into the UK by the Romans and has since become naturalised. A medium-sized umbellifer, it is an invasive weed of shady places, gardens and roadsides.

Although introduced by humans, the fallow deer has been here so long that it is considered naturalised. Look out for groups of white-spotted deer in woodland glades.

Buddleia is a familiar shrub, well-known for its attractiveness to butterflies. It is actually an introduced species, however, that has become naturalised on waste ground, railway cuttings and in…

Fennel has feathery leaves and open, umbels of yellow flowers. It was probably introduced by the Romans for culinary use, and is now a naturalised species of verges, waste ground and sand dunes.…

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…

Tall melilot was introduced into the UK as a fodder crop, but has now become naturalised. It displays golden, pea-like flowers on tall spikes, which are followed by black, hairy seed pods.

Red valerian was introduced in the 1600s from Europe, but is now naturalised in the UK. Its pinky-red flowers grow from old walls, roadside verges, railway cuttings and cliffs, and provide nectar…