Last reviewed 17 December 2018

Laura King outlines the legislation and steps that organisations need to take to protect against invasive plants.

They are renowned as aggressive, destructive, destroyers of biodiversity, a danger to property values and costly to remove. Invasive non-native species (INNS) are often in the news, and the news is rarely positive.

Take for example, Japanese knotweed — characterised as a thug of a plant; stories abound that it grows through concrete, destabilises river banks, “comes back from the dead” and cannot be treated.

Some of these stories do have a basis, in fact, it was reported that removal of Japanese knotweed from just 10 acres of the Olympic Park in London cost in the region of £70 million. Figures from the UK’s INNS Strategy reckoned that the annual cost to the UK economy was in the region of £1.7 billion and according to research released in September this year the weed wiped £20 billion off the total value of the UK property market. To make matters worse, results from the world’s largest study into Japanese knotweed treatments found that there was no definite way to eradicate the plant completely.

Are INNS really so bad?

With such bad press, it’s no wonder that INNS have a reputation. Whether this is fair or not is a matter of debate.

For example, research published by global infrastructure services firm AECOM and the University of Leeds showed that reports of actual damage to buildings from Japanese knotweed were in fact quite rare and certainly no worse than other plants, such as Buddleia.

Furthermore, the news and legislation focuses on a couple of INNS, specifically, those that have a big impact on their local area and often do result in a localised, large-scale loss of biodiversity. However, it should be remembered that there are many other non-native species found within the UK which are not targeted. Many are unknown, less obvious, or relatively unstudied; others are widely accepted, such as many of our farmed animals and crops.

However, regardless of whether or not INNS should have such a fearsome reputation, there are still clear responsibilities for landowners with regard to controlling these plants and they do need to be taken seriously.

What does the law on INNS say?

In England and Wales, the control of INNS is largely covered by the Wildlife and Countryside Act 1981 that states that it is an offence to plant or otherwise cause INNS to grow in the wild. The species targeted by the Act are listed in schedule 9.

A few years ago, the responsibility to protect land from damage by INNS was bolstered by the Infrastructure Act 2015 which introduced species control orders and agreements for these schedule 9 plants. These agreements and orders mean that landowners approached by the relevant authority are required to take measures to control INNS on their property. In an agreement, the actions required are decided by both parties; a control order is put in place if certain conditions are satisfied, for example if an agreement cannot be reached.

Other legislation may also apply to the control of INNS. For example, any spraying of herbicides must comply with the law, as does any removal of waste containing invasive species. Japanese knotweed, for example, is classed as controlled waste under the Environment Protection Act 1990.

The EU and INNS

The EU Invasive Alien Species Regulation came into effect in the UK in early 2015. It lists 49 species to which additional restrictions apply.

Although most of the species are of marginal importance to the UK, it does include giant hogweed and floating pennywort. In addition, the Royal Horticultural Society lists two ornamental plants, water hyacinth and skunk cabbage, which are widely grown in the UK. Although having these species present on grounds will not result in prosecution, any landowner will need to ensure that the plants do not spread.

In early 2018, the Government launched a consultation on how to enforce the penalties required under the regulation. Broadly speaking, respondents were in favour of enforcement through existing frameworks, but were also in favour of tougher sanctions. As a result, the Government has promised to look into the possibility of larger fines for persistent offenders as well as the feasibility of creating new criminal offences.

It should be noted that as the Invasive Alien Species Regulation is already on the statute books, it will continue to be in place post-Brexit under the European Union (Withdrawal) Act 2018.

Plant ASBOs and nuisance

In 2014, the law did no favours for INNS when the legislation concerned with preventing anti-social behaviour was reformed through the Anti-social Behaviour, Crime and Policing Act 2014. The Act created Community Protection Notices, sometimes referred to as Plant ASBOs, which could be served on individuals or companies to take action to control INNS.

More recently, in a landmark ruling earlier this year, three judges awarded damages to two households whose properties had been invaded by the roots of Japanese knotweed from adjoining land owned by Network Rail. The claim was brought on the basis that the plants were causing a nuisance, and that they interfered with quiet enjoyment of the property.

The ruling found that Network Rail had been in breach of its duties as a landowner and that its treatment of the plant had been inadequate. With obvious consequences for landowners across the country, Network Rail’s appeal was unsuccessful and it was ordered to pay compensation to the homeowners.

What can I do to tackle INNS?

Given some of the well-known difficulties in tackling INNS, it might well be an impossible, and impossibly expensive, task to completely eradicate INNS on landholdings. However, to avoid legal challenges, the problem cannot be ignored. One option is to adopt a targeted risk-assessed approach, the rationale for which should form the basis of an action plan.

This would include the following steps.

  1. Know where your invasive species are — map out all instances of INNS on landholdings. Here, regular monitoring is key. Many of the plants in question will establish quickly and expand rapidly; therefore early identification and action will reduce the cost and scale of any management programme.

  2. Conduct a risk assessment for each location — for example, are the plants near to boundaries, water courses or buildings? In some cases, immediate action should be taken. For example, the sap of giant hogweed is very toxic and cause severe burns. As such, if it is found, efforts should be made to restrict access.

  3. Establish how the INNS became present — it is likely that this will involve a co-ordinated approach with others.

  4. Draw up a management plan — this should detail what actions are required. It should include training for staff as well as sustained monitoring and management of sites.

The GB Non-native Species Secretariat (NNSS) is a good source of information on how to identify INNS, as well as offering advice on management options. It is also recommended that where INNS are present, early advice is sought from an expert.

In summary

  • Stopping the spread of INNS is a legal responsibility and companies can be sued for damages if they do not properly control certain species.

  • Swift and sustained action against the most invasive of plants is the best policy.

  • A targeted, methodical approach is one option for control. This should be based on a mapping exercise, risk assessment and, where necessary, professional advice on the best management methods.

See also Invasive species — not always hostile.