How are invasive plants a problem?

Many invasive plants were originally introduced for use in gardens and ponds, but have since spread or been deliberately planted in the wild. Their harmful impacts can affect the environment, wildlife, economy or even our health and how we live. Aquatic plants, those which grow in water such as pond and aquarium plants, can be particularly invasive in the wild as many are extremely fast growing and can grow from a tiny plant fragment.

Below are a few examples of the problems that invasive plants can cause if they become established in the wild.

Find out how you can help to prevent the spread of invasive plants

Threaten rare habitats and wildlife

Image of Monbretia crocosmia spp green shoots and red flowers Image of Tanacetum vulgare green shoots and yellow and purple flowers Image of the Tansy beetle (purple and green shell) on a yellow flower

Some species are dependent on a single plant. The highly endangered tansy beetle (left) was reduced to a single population when its sole food source, the native tansy plant (centre left), became rare, partly due to competition from invasive Himalayan balsam (centre right). The Tansy Beetle Action Group has been controlling Himalayan balsam to restore sites across the beetle’s range.

The Lizard Peninsula in Cornwall is home to almost half our native wildflower species, many of which are rare. A number of invasive plants have been introduced here, including montbretia (right) which reduces biodiversity by crowding out other plants, and hottentot fig which can change the nutrient composition and acidity of the soil.

Spread plant diseases

Green folliage of Rhododendron plants

Rhododendron is a host of the plant disease organisms Phytophthora ramorum and P. kernoviae which are a serious threat to native species including oak, beech and larch.

Clog waterways and increase the risk of flooding

Barrier across a waterway partly blocked by plants growing out of the water Purple flowers of Himalayan balsam in bloom on a riverbank

In France, where water primrose (left) has become widespread, it blocks waterways and overgrows ponds and lakes forcing out native wildlife and causing flooding. It is currently only established in a small number of sites in England and Wales, but if it were to establish widely in Britain, it would cost millions of pounds to manage. Any suspected sightings should be reported through iRecord. Plants that grow on riverbanks are also a problem. Himalayan balsam (right) dies back completely over winter leaving the riverbank unstable and vulnerable to erosion, increasing the risk of flooding.

Damage buildings and infrastructure

Green shoots of a Japanese knotweed plant Broken concrete with a Japanese knotweed shoot bursting through

Japanese knotweed is extremely difficult to eradicate and can cause structural damage to roads and houses growing through asphalt and concrete. This can lead to significant delays and costs to development, estimated at £150 million a year.

Interfere with recreation

Green aquatic plant spread across a large expanse of water A canoeist navagating through a mass of aqautic plants

Large mats of invasive aquatic plants can be difficult for boats, canoes and kayaks to pass through, and can interfere with angling. Under the right conditions floating pennywort can grow up to 20 cm a day. It rapidly forms dense mats which affect oxygen levels in the water, crowd out and kill off native wildlife, and damage habitat.

Harm human health

A close up of a red and bumpy rash on the the thigh of a person Giant hogweed flowering on a riverbank with city buildings rising in the background

A tiny amount of the sap of giant hogweed can cause nasty skin blistering on exposure to sunlight. The affected area can remain vulnerable for several years.

Find out how to prevent the spread of invasive plants.

Thin strip of image show tree trunk and bark