Injurious Weeds Surveys

What are Injurious Weeds?

Injurious weeds are a specific group of native plant species classified as harmful weeds under the Weeds Act 1959.

Unlike non-native invasive species such as Japanese knotweed or Himalayan balsam, injurious weeds are plants that originate in Great Britain, but they share the ability to spread rapidly and cause considerable damage to pasture, forage production, crop yields and grazing animals.

These invasive plants are typically found on bare ground and land under crop production; if many plants are involved, agricultural activities can be put at high risk.

In other parts of the world, including Australia, Canada and the United States, these plants are often referred to as noxious weeds, a term used more broadly to cover various forms of problematic vegetation and many species of dangerous weeds.

The Five Listed Species

The Weeds Act 1959 designates five species as injurious weeds in England and Wales:

• Common ragwort (Senecio jacobaea)
• Spear thistle (Cirsium vulgare)
• Creeping or field thistle (Cirsium arvense)
• Curled dock (Rumex crispus)
• Broad-leaved dock (Rumex obtusifolius)

Each of these species is capable of spreading quickly across a site if left unmanaged, and some, particularly the yellow flowers of common ragwort, are highly toxic to grazing horses, according to the British Horse Society, and subject to the Ragwort Control Bill.

Other livestock can also be harmed by ingesting common ragwort and other plants of a noxious nature.

Relevant Legislation

Several pieces of legislation are relevant to injurious weeds and the management of invasive plant species more broadly in the British Isles.

The Weeds Act 1959 is the primary legislation governing injurious weeds in England and Wales. It enables DEFRA to serve enforcement notices on anyone responsible for land where the five listed species are causing or are likely to cause harm. Natural England may also become involved in cases of non-compliance.

Section 14 of the Wildlife and Countryside Act 1981 makes it an offence to plant or otherwise cause the spread of any listed invasive species, whether native or non-native.

The Environmental Protection Act 1990 classifies removed plant material as controlled waste, meaning it must be disposed of correctly to prevent further spread and environmental contamination.

What is an Injurious Weeds Survey?

An injurious weeds survey is an ecological assessment carried out to identify, map and manage specific native plant species that are legally controlled under UK legislation.

These plants, commonly known as injurious weeds, can cause significant harm to agricultural productivity and livestock, and their presence on a development site can create complications for planning applications if they are not properly addressed.

A qualified ecologist will visit the site, identify any of the listed species present, assess the extent of any infestation and produce a report with recommended management measures.

The findings will give you and your local planning authority the information needed to ensure the development can proceed without unresolved ecological or legal issues.

Why Might You Need an Injurious Weeds Survey?

If one or more of the five listed species is found or suspected on a proposed development site, public bodies such as local authorities will want to see evidence that the issue has been properly assessed and that reasonable efforts are being taken by land managers to control it.

An injurious weeds survey provides exactly that. It demonstrates to planning officers that the ecological and agricultural risks posed by the plants have been professionally evaluated and that a credible management strategy is in place.

Without this, a planning application may be delayed or refused on grounds of insufficient ecological information.

Beyond the planning process, landowners and developers are subject to a legal requirement under the Weeds Act 1959 to prevent the spread of injurious weeds to neighbouring land.

The Department for Environment, Food and Rural Affairs (DEFRA) has the power to issue enforcement notices where this duty is not being met, so obtaining a survey and following through on its recommendations is important both for gaining planning consent and for meeting wider legal obligations.

Injurious Weeds Survey Process

The survey process typically follows four main stages.

Initial Site Assessment

An ecologist will carry out a thorough inspection of all vegetation across the site, identifying and recording any injurious weed species present to assess their ecological impact.

Observations will note relevant conditions such as land use and disturbed soil areas, which can contribute to weed spread, along with the location, density and current extent of any growth.

Mapping and Risk Analysis

Any weed infestations will be mapped and areas of active or likely future spread will be flagged. A risk assessment will determine whether the weeds are likely to affect the outcome of a planning application and what level of management intervention is required.

The potential impact on a large area of adjacent land, including neighbouring gardens and agricultural holdings, will also be considered.

Weed Management Plan

Based on the site visit findings, the ecologist will recommend a management strategy tailored to the species and level of spread present on the site.

Control measures may include herbicide treatment, physical removal or a combination of both, along with soil management guidance to reduce the risk of re-establishment.

Monitoring and Reporting

Depending on the scale of the infestation, the invasive plants in question and survey results, ongoing monitoring may be recommended to confirm that management measures are effective.

A formal injurious weeds survey report will be produced, setting out the findings and the agreed management approach, which can be submitted alongside or in support of a planning application.

Injurious Weeds and Other Invasive Species

Injurious weeds surveys often form part of a wider assessment of vegetation on a site. In some cases a consultant may be called in to investigate complaints from the general public about invasive plants such as creeping thistle on a site.

If a preliminary ecological appraisal or other survey identifies the potential presence of invasive non-native species such as Japanese knotweed, giant hogweed or Himalayan balsam, a separate invasive species survey will be required. These listed plants are governed by different legislation and require their own management plans.

If your site may have both injurious weeds and invasive non-native species, it is worth discussing this with your ecological consultant at the outset so that all relevant surveys can be planned and coordinated efficiently, ensuring that you stay on the right side of legislation.

Booking an Injurious Weeds Survey

The first step is to identify an ecological consultancy with experience in carrying out injurious weeds assessments and producing reports that meet the requirements of your local planning authority.

The ecologists should hold appropriate qualifications and be able to advise on the full scope of vegetation management measures your site may require.

Use our free service to get a fast, no-obligation quote. For further information, fill in the form at the top of this page, and an expert will contact you to help your project move forward.