Invasive weeds can cause a range of environmental problems. They suffocate other plantlife, and some are poisonous to animals. Some can damage buildings as they grow. Many are not native to Britain, so the pests and diseases that stop them spreading in their countries of origin are not present here. Some of these weeds grow in grass verges or along river banks. If you spot any of the following weeds in South Gloucestershire, please report them to us. If we are responsible for the land where they are growing, we will deal with them, and if not, we may ask the landowner to deal with them to stop them spreading.
If you spot them on your own land, you should get rid of them quickly – seek specialist advice on what to do. It is illegal to plant them, or cause them to spread in any way.
Common Ragwort
This is a native biennial plant that grows up to one metre tall. It has a large, densely packed head of bright yellow flowers. It is very poisonous to horses, cattle and other animals, so must be kept away from agricultural land. It can also be toxic to humans, and you must avoid touching it. Ragwort is subject to the Weeds Act of 1959, so landowners can be served with enforcement notices to make sure they stop it from spreading.
Japanese Knotweed
This is a perennial plant that forms dense stands of tall, hollow, speckled canes during summer, which die back in autumn. During spring, reddish purple shoots appear and the plant grows rapidly – up to three metres (10 feet) tall. As leaves unfurl, the plant turns green.
Knotweed can damage hard surfaces such as tarmac as it grows. It can grow through the floors of houses, occasionally even through the foundations. It is best to deal with it while it is still small.
Giant Hogweed
This perennial can grow up to seven metres (20 feet) tall. It looks like a larger version of Common Hogweed or Cow Parsley. It has stout, dark reddish-purple stems and spotted leaf stalks that are hollow and produce sturdy bristles. It flowers from mid-May to July, with white flowers clustered into an umbrella head that can be up to 0.8 metres (2.5 feet) across.
Giant Hogweed can cause severe blisters on your skin – if you touch it, wash the area immediately.
Himalayan Balsam
This is an annual herb that can grow up to two metres (6.5 feet) tall. It has upright, purple-tinged stems and white, pink or purple flowers that appear from July to October. It spreads very quickly, particularly along riverbanks or in wetlands.