Invasion sparks war on weeds

Giant Hogweed at Ettrick Riverside, Selkirk.
Giant Hogweed at Ettrick Riverside, Selkirk.

A WAR on weeds is under way in the Borders targeting the pesky invasive foreign plants the Giant hogweed and the Japanese knotweed.

The sprawling plants are a blight along river banks and on farmland. And the Giant Hogweed carries a poisonous, burning sap that can lead to permanent disfigurement.

Both these invaders, alongside several others, are seen as a major threat to the local environment in the Borders.

They are aggressive colonisers that smother the life out of native plants – and the banks of the Tweed and other rivers and burns have been particularly hit.

There have been some major victories in the battle against the green giants, but conservationists know the battle is far from being won.

And leaflets offering advice to landowners who are facing problems from the plants have again been published by Drygrange-based Tweed Forum.

Foreign plants have inhabited the River Tweed catchment since the 19th century – some were brought here accidentally in goods shipped in from abroad, while others spread from specialised domestic gardens.

The main problem is that they provide a poor habitat for mammals, birds, fish and insects, and shade-out native plants.

Dead stems from the massive plants can clog watercourses and lead to flooding, while root erosion leads to river banks collapsing and damage to walls, pipes and houses.

Both invasive species are now at their most prolific.

The perennial giant hogweed can grow to 16ft with leaves of three feet.

White flowering heads spread to 15 inches across.

Its hollow stems are a temptation for youngsters who turn them into make-believe telescopes or pea-shooters – sometimes with horrendous results.

Tim Barratt, the Tweed invasives officer, stressed: “The stems, leaves and sap contain a poison than can result in serious blistering that reacts badly when exposed to sunlight.

“The reaction to the poison can occur up to 48 hours after only very slight contact and even through light, summer clothing.

“All blistering should be treated as a burn and in severe cases, medical advice sought as untreated blistering can lead to permanent skin damage resulting in recurrent dermatitis.”

Giant hogweed can be partly controlled by using grazing sheep and cattle which are immune to the plant’s poison.

But pigs suffer the same ill effects as humans.

Careful cutting and digging out the tap root also works, but care must be taken as to how the plants are disposed off.

Grazing and cutting are only of limited advantage in the attack on Japanese knotweed, leaving chemicals as the best means of assault.

But experts say that whatever method is used, great care must be taken – especially in the use of chemicals.

Tweed Forum can provide advice and can be contacted on; by emailing; by calling 01896 849723 or writing to Tweed Forum, South Court, Drygrange Steading, Melrose.