Need a Japanese Knotweed Survey?

What Is Japanese Knotweed?

Japanese knotweed (synonyms Fallopia japonica, also known as Reynoutria japonica and Polygonum cuspidatum) is a rapidly growing, clump forming herbaceous perennial and an invasive non native plant species. Knotweed can grow in a variety of soil types and can quickly colonise areas such as roadsides, hard surfaces, riverbanks, waste ground, brownfield sites and gardens.

Japanese knotweed is a highly specific plant from the buckwheat family with a good potential to cause serious structural and legal problems for landowners. Often confused with similar plants such as giant knotweed, Russian vine, elephant ears, or donkey rhubarb, it has spread far beyond its native range and is now established in places as distant as British Columbia.

Its growth can damage buildings, drains and boundaries and improper disposal may be classed as anti social behaviour under Part II of the Crime and Policing Act, bringing legal consequences. Industry bodies such as the Property Care Association warn that mismanagement can reduce property value and complicate sales, making early identification and professional treatment essential to avoid escalating risk.

Identifying Japanese Knotweed

Spring/Summer: Tall, bamboo-like new growth appears with large green, heart or shovel shaped leaves in the growing season. Stems may have red or purple flecks. Small clusters of white flowers appear in late summer.

Early Autumn/Winter: Leaves die back, and dead stems become brittle and brown. The plant retreats underground but remains alive and ready to regrow in spring. Its rapid growth – up to 10 cm per day – makes early identification vital.

If you suspect the presence of Japanese knotweed on your property, it’s essential to arrange a professional survey. A qualified specialist can confirm its identity and assess the extent of the issue, helping you take swift and effective action.

Where Did Japanese Knotweed Come From?

Originally native to Japan, the plant was introduced to Europe in the 1800s as a garden plant by botanist Philipp von Siebold. Praised for its appeal as an ornamental plant, it was planted widely before its invasive nature became apparent. This difficult weed has since spread across Great Britain, often unknowingly through contaminated soil and watercourses.

Why Is Japanese Knotweed a Problem?

Japanese knotweed is both strong and capable of accelerated growth; it can thrive in cracks and grow within confined areas to cause significant harm to a property or plot of land. This clump forming herbacious perennial grows in dense thickets, often overwhelming native vegetation.

Its persistent or continuing nature and fast-growing rhizomes mean that small areas can quickly expand. This alien species has an extensive root system; it regenerates from fragments of rhizome and stem; often attempts to dig it out result in its spread. Knotweed material and rhizomes can remain dormant for many years before growing rapidly. Issues with Japanese knotweed often occur when it spreads from an untreated area into neighbouring gardens.

Left untreated, this non native species creates problems for property owners as it can:

• Damage building foundations, paving, walls and drains
• Overwhelm other plants
• Interfere with land development projects
• Affect property values and planning applications
• Lead to mortgage refusals
• Spread to neighbouring property

Legal Status in the UK

Japanese knotweed is listed under:

• Schedule 9 of the Wildlife and Countryside Act 1981. It’s an offence to plant or cause it to grow in the wild.
• The Environmental Protection Act 1990. Classified as “controlled waste,” Japanese knotweed must be disposed of at licensed landfill sites.

Allowing Japanese knotweed to spread from your property may be considered a legal offence; it therefore carries a threat of legal action, particularly if it impacts neighbouring gardens or land.

Is Japanese Knotweed Poisonous?

No. It is not toxic and does not pose a risk to human or animal health through touch or ingestion.

Japanese Knotweed Surveys

If this invasive weed is suspected to be growing on your land, you will need to obtain professional identification and advice on controlling Japanese knotweed or destroying it. Commissioning a survey is critical. A Japanese knotweed survey provides:

• Accurate identification of this invasive weed
• Assessment of spread and severity
• Legal guidance and reporting obligations
• A detailed report with recommendations for treatment or how to remove Japanese knotweed. This report is often required for mortgage applications and development projects.

Cost of a Survey

Prices vary depending on the size of the site and complexity of the infestation. Costs can range from £2,000–£3,000 for herbicide treatment to £100,000+ for full removal across larger or heavily affected areas.

Mortgage Implications

Many lenders are cautious about properties with Japanese knotweed. A survey report and a robust Knotweed Management Plan (KMP) may be required to satisfy lenders and secure a mortgage.

The Royal Institution of Chartered Surveyors (RICS) Knotweed Risk Categories

The RICS categorises knotweed presence as follows:

• Category 1: No knotweed on site or nearby
• Category 2: Knotweed on neighbouring land, more than 7m from the boundary
• Category 3: Knotweed within 7m of the boundary
• Category 4: Knotweed on the site, more than 7m from habitable space
• Category 5: Knotweed on site, within 7m of habitable space

Categories 4 and 5 usually require immediate attention and a formal Japanese knotweed survey.

How to Remove Japanese Knotweed

The main treatment options include:

• Chemical treatment: Glyphosate-based herbicides applied to plants: this can take several seasons
• Excavation: Physically removing contaminated soil (most effective) and knotweed material
• Combination approach: Often used by professional contractors to ensure the success of a plan to remove the invasive weed

Specialist companies can provide treatment plans with insurance-backed guarantees for peace of mind.

Japanese Knotweed Management Plans (KMP)

Following a survey, a KMP outlines how the knotweed will be treated or monitored. This is often a requirement for:

• Mortgage applications
• Land development projects
• Environmental compliance

The plan may include herbicide treatment, an excavation strategy, monitoring timelines, and safe disposal methods.

Reporting Japanese Knotweed

You are not legally required to report knotweed on your own land, but doing so helps protect surrounding areas. If you spot it:

• Contact your local council
• Report to the Environment Agency (especially if the plant is sighted near watercourses or fly-tipped) or notify National Rail (if it is located near train lines)

Early reporting helps prevent further spread and legal complications.

Suspect Japanese Knotweed? Take Action Now

If you think Japanese knotweed may be growing on or near your land:

• Contact a qualified ecologist or invasive species specialist for further information
• Arrange a professional survey
• Begin treatment planning as soon as possible

With proper assessment and management, the challenges of Japanese knotweed and other invasive species can be overcome, protecting your property and investment.