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Invasive Species

Invasive Species

Invasive non-native species have been introduced into an area where their natural predators, competitors and diseases are absent.

What are Invasive Species?

Invasive species are plants or animals that spread rapidly and out-compete other species.

Non-native invasive species are animals or plants that have been introduced from outside the UK (non-native), which kill or out-compete native species or destroy wildlife habitats. Schedule 9 of the Wildlife and Countryside Act 1981 lists the non-native invasive species, which are illegal to release into the wild.

Why are they a problem?

Invasive species cost us around £1.7 billion every single year. They challenge native species and habitats, can affect human health and even contribute to extreme environmental events such as flooding in the case of some plant species.

Once a non-native species is introduced, the problem often escalates as the species spread further, and can be difficult to control due to the isolated and inaccessible nature of parts of our countryside.

Problem Species

Not all non-native species are detrimental. Only a small percentage have a negative impact. Listed below are a selection which are a particular problem in Surrey.


Latin Name

Signal Crayfish

Pacifastacus leniusculus

Canada goose

Branta canadensis


Neovison vison

Ring-necked parakeet

Psittacula krameri



Latin Name

Himalayan Balsam

Impatiens glandulifera

Japanese Knotweed

Fallopia japonica


Aquatic Plant

Latin Name

New Zealand Pygmyweed

Crassula helmsii

Water Fern

Azolla filiculoides


Myriophyllum aquaticum

Floating Pennywort

Hydrocotyle ranunculoides

Curly Waterweed

Lagarosiphon major

How You Can Help

When buying plants and flowers, try to buy as locally as possible and avoid imported plants, which may harbour devastating diseases that our native species have no resistance to.

Avoid purchasing non-native invasive species such as:

Garden Plant

Latin Name

Variegated Yellow Archangel 

Lamiastrum galeobdolon subsp. argentatum

Virginia Creeper 

Parthenocissus quinquefolia

Three-cornered Garlic 

Allium triquetrum


Crocosmia x crocosmiiflora


Rhododendron ponticum

Giant Rhubarb

Gunnera tinctoria

Japanese Rose 

Rosa rugosa

Few-flowered Leek 

Allium paradoxum

Yellow Azalea 

Rhododendron luteum