Why Invasive Plants Pose Big Challenges for London

What are invasive weeds and why are they a problem in London?

Invasive weeds are plants that are typically non-native to the UK and have evolved to become dominant species that threaten our native species. Common plants found across London include Japanese knotweed, Horsetail and Himalayan balsam, but there's also some lesser-known plants such as Japanese rose, Tree of heaven and Three cornered leek.

Is Bamboo an invasive plant in London?

There are several species of Bamboo, the most invasive being the 'running' variety. Being an ornamental garden plant, many London properties planted it as a screen or simply as a feature. However, Bamboo grows much the same as knotweed, it encroaches underneath boundaries into neighbouring properties causing much the same issues. As yet Bamboo is not bound by legislation, however neighbour disputes are common in. 

Because London is a dense urban environment including the Camden, Croydon, Lambeth, Hackney, Westminster and Greenwich boroughs all with a complex network of railways, waterways and high-value real estate, these concerns are often more acute than in rural areas. Let's unpack the top 3 concerns; property value, infrastructure and transport risk and legal liabilities.

1. Property value and mortgages (The "knotweed" fear)

For many Londoners and London boroughs, the primary concern is the financial ruin associated with Japanese Knotweed.

• Mortgage refusal: Banks are notoriously cautious. If knotweed is found within 7 meters of a London property, lenders may refuse a mortgage unless a professional management plan (with an insurance-backed guarantee) is in place. That's why a herbicide treatment plan is often the best option for buyers and sellers of properties with knotweed or other invasive plants. It provides the reassurance people look for.

• Devaluation: An infestation can knock 5% to 20% off a property's value. In the expensive London market, this can represent hundreds of thousands of pounds on the average residential property and is obviously a much higher cost to commercial developers if not managed appropriately and at the right time (pre-contract commencement).

• Damage: Residents worry about the plant's ability to grow through cracks in concrete, drains, and garden walls.

2. Infrastructure & transport risks

London’s infrastructure acts as a "superhighway" for invasive species.

• Railways & canals: Network Rail and the Canal & River Trust are constantly battling weeds like Himalayan balsam and Japanese knotweed which destabilise riverbanks and railway embankments, leading to delays and safety risks. Taking control in early growing season is important to stop the spread. An invasive plants specialist will survey the area to assess the extent of the infestation and ensure works treat or remove all of it in a compliant manner.

• Public safety: Species like Giant hogweed are a specific concern because their sap causes severe skin burns. Local authorities prioritise its removal in high-traffic areas like the Thames Path or borough parks and green spaces. It’s vital for H&S reasons alone to use a highly trained invasive plants contractor who know what they’re doing.

3. Legal liabilities

Because landowners have legal responsibilities for invasive weed control in the UK, Londoners and London property developers are often worried about the legal implications of invasive plants, particularly with knotweed "neighbour dispute" can be a dominant factor when it comes to weed control.

• Private nuisance: Under UK law (and strengthened by recent court cases), if you allow an invasive weed to spread from your property or land not neighbouring property or land, you can be sued for damages and the cost of removal. Working together with neighbours to get rid of the invasive plants (especially knotweed or bamboo) removes the risk of it spreading or returning for both parties.

• Disposal laws: It is a criminal offense to dispose of invasive weeds listed on Schedule 9 of the Wildlife & Countryside Act in regular "green waste" bins, or to fly tip them. Professional disposal is expensive, leading to concerns about the high cost of compliance, but using a professional contractor eliminates this concern as they are licensed to deal with this type of waste.

The Environmental Controls Group has long-standing contracts with many London authorities, such as Hounslow and Haringey who understand how important controlling invasive species is for their parks and green spaces. Most boroughs now include an invasive weed management plan in their targets and we work with our local authority clients to ensure they meet their sustainability goals too.

Because Japanese knotweed is a legal and financial liability, several boroughs have updated their reporting and enforcement systems for 2026:

• Waltham forest: Operates a "Fix My Street" reporting system specifically for invasive species and takes formal legal action against private landowners if they allow plants to spread onto public land.³

• City of London: Through its Biodiversity Action Plan 2021–2026, the Square Mile actively manages over 200 sites with a focus on early detection to prevent damage to historic buildings.

• Tower Hamlets & Haringey: These boroughs have active "Pesticide-Free" campaigns that work alongside council teams to manually clear invasive species in high-density parks.

High-Risk Zone Management (rivers and rails)

Boroughs along the Thames and the Lea Valley are part of the London Invasive Species Initiative (LISI). In 2026, they are prioritising:

• Giant Hogweed: Actively controlled in Richmond, Hounslow, and Kingston to prevent public health incidents (skin burns) on the Thames Path.

• Himalayan Balsam: Targeted through "Balsam Bashing" volunteer events in Enfield and Redbridge to prevent riverbank erosion.

How to check your specific borough

Most London councils now provide a digital map or a "Report It" app specifically for invasive species.

• If you are in Bromley look for...The Biodiversity Action Plan.

• Waltham Forest look for...The "Japanese Knotweed and Other Invasive Plants" reporting portal.

• Hammersmith & Fulham look for...The "Ecological Emergency" policy updates.

• Anywhere in London look for...The GiGL (Greenspace Information for Greater London) database.

The Environmental Controls Group – here to help London control invasive species.