AN invasive plant is taking over derelict sites and crumbling brickwork across Barrow.

Buddleia is identified by its long, slender clumps of flowers, usually lilac but also blue, deeper purple or white, at the end of long, arching branches.

Car parks, industrial land and even houses have fallen victim to the fast-growing plant. Buddleia, native to parts of China and Japan, was first introduced to Europe in the late 19th Century and is viewed by the Department for the Environment, Food and Rural Affairs as an invasive non-native species.

Gardeners are being asked by Defra to remove seed heads after flowering to prevent its spread.

The plant has also been causing problems for Network Rail which regularly cuts down large buddleia before removing or killing the stumps, sprays small buddleia with herbicide, and uses weed-killing trains to keep the network clear, while staff use portable sprayers at stations.

The plant can cause damage to buildings, such as crumbling brickwork - its tiny wind-blown seeds can germinate in decaying mortar.

Butterfly Conservation is one of the wildlife organisations that recommends planting buddleia for its summer nectar that the creatures feed on but admits the plant has to be treated with caution.

The charity says the plant can cause serious problems on conservation sites. It advises against planting buddleia where it may be unmanaged and recommends gardeners remove seed heads.

The plant has sold steadily and is very popular with the public, while buddleia other than the davidii species pose no threat, and seedless clones are available, he explains.

Guy Barter, chief horticultural adviser at the Royal Horticultural Society, said: "We do suggest de-seeding it, but in urban areas there is often so much on wasteland that even if every gardener dead-headed their buddleia the effect would not be very great."