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Invasive plants

Japanese knotweed © Laurie Campbell

Whether you are interested in the environment or not, the problems caused by non-native invasive species affect us all.

What's the problem?

For a start, they cost us billions of pounds to put right - £1.7 billion every single year in Britain alone, according to the Government. Their spread is recognised as one of the greatest threats to the economic well-being of the planet.

Then there's the structural damage to roads, houses and flood defences. Many invasive plants can re-grow from just a tiny fragment of plant matter left in the soil or water meaning it is often impossible to clear an area of unwanted plants in one go - it can take years to put right. Damage to your prospects of selling your home, clogged waterways which can increase flood risks, reduced crop yields and skin-burning sap are a few other ways in which invasive plants invade our lives.

As far as nature is concerned, invasive plants often form monocultures, taking over an area so that they are the only plant growing there. Most invasive plants grow very quickly, preventing light reaching slower-growing or shorter species, and so causing those less competitive plants to die off (while Rhododendron leaves contain a chemical that can mildly suppress seed germination, this is insignificant compared to the effect of shading from the fast-growing canopy). By decreasing plant diversity, the creation of a monoculture can also remove habitats for animals.

To make things worse, non-native invasive plants are often unpalatable to native herbivores like invertebrates. Monocultures of non-native invasive plants can, therefore, lead to reduced food availability in an area as well as reduced habitat. In waterbodies, invasive plants can spread over the surface of the water reducing light and oxygen levels below which can be damaging for both plants and animals.

Do I have any in my garden?

Although the damage caused by invasive non-native plants is real and burgeoning, only a small number of the 70,000 or so non-native plants available to buy in Britain actually pose a risk.

The majority of these non-native plants are unlikely to cause environmental damage now or in future, and we don’t want to unnecessarily curb trade or the enjoyment of plants by gardeners and pond-keepers by suggesting non-native plants shouldn’t be used.

However, the impact that the few highly invasive non-native plants have on sites throughout Britain should not be ignored. So how can we hope to differentiate between plants we should worry about and those which are unlikely to ever be of concern?

The current method is quite time-consuming and so Plantlife has developed a 'Rapid Risk Assessment' screening process. Click here to find out more about this.

As a general rule, Plantlife recommends avoiding the following plants (click link below to download):

• List of non-native invasive species to avoid

How can I help?

It may look pretty, but the water primrose can clog waterways, devastate habitats and cause expensive damage. © Trevor Renals

The simple fact is that more than 60% of invasive plants in the UK are garden escapees. If we as a nation of gardeners have (inadvertently) caused much of the problem, then the good news is that we can solve much of the problem by the choices we make.

Most invasive species are still available for sale, with many garden centres, pet shops, aquarists, DIY stores and supermarkets across the country continuing to sell damaging species. Although the Government has powers to ban the sale of invasive plants, no sales bans are yet in place. But you can do your bit now: tell store managers that you don't want to see non-native invasive plants on sale and don't buy them.

Even if you are a responsible gardener or fish-keeper and dispose of problem plants safely – by composting or burning them or using a municipal garden waste collection – they may be carried into the wild by the wind or by birds and other animals outside of your control. That's why we think avoiding non-native invasive plants in the first place is the most effective choice.

We believe there are plenty of non-invasive plants available to gardeners, landscapers and pond/fish-keepers. That’s why we have produced a series of booklets to help you choose plants that are less likely to cause problems to the environment should they escape from your garden or pond. For more information click on the 'Plants you can use in place of invasive non-natives' link in the left hand menu

The bottom line:

NEVER release ANY garden or aquarium plants into the wild -

• Don't tip them down land drains,

• Don't dump them in the countryside,

• Don't throw them into your normal waste bin.

• Do compost or burn them or use your local council garden waste collection.

Further information

Click on any of the titles below to download a PDF on the subject:

• What is the law regarding non-native invasive plants?
• How do I remove a non-native invasive plant from my land?
• Which species do Plantlife believe are a threat?
• How can I help?
• Can you tell me more about the history and terminology of non-native invasive plants?