The Japanese knotweed glossary

Rhizome

The underground stem system knotweed lives and spreads through - dark and knobbly outside, bright orange inside when snapped. A fragment the size of a fingernail can regrow a whole plant, which is why disturbing knotweed usually spreads it. See how deep do the roots go?

Crown

The woody growing point at the base of the canes, sitting at or just above soil level. Next spring's buds form on the crown - which is why cutting canes down changes nothing underneath.

Stand

A distinct patch of knotweed growth. Surveyors map stands, measure their extent and distance from buildings, and track them across visits.

Cane

A single knotweed stem - green and bamboo-like in summer, dry and orange-brown when dead in winter. Hollow, segmented, and light like a straw when snapped.

Node

The joint on a cane where a leaf emerges. Knotweed's leaves alternate node by node, giving the stem its characteristic zig-zag.

Dormancy

Knotweed's winter state: everything above ground dies, while the rhizome lives on ready to shoot in March. Dormant knotweed is the easiest kind to miss - see knotweed in winter.

Stunted ("bonsai") regrowth

The small, distorted growth knotweed puts out after herbicide treatment - tiny leaves, low sprawl, easy to mistake for a harmless seedling. It signals a suppressed but living rhizome, and it's one of the hardest forms to spot.

Encroachment

Knotweed rhizome crossing a boundary into neighbouring land. Encroachment is what turns knotweed from a gardening problem into a legal one.

Private nuisance

The civil wrong committed when knotweed is allowed to spread from one property to another. It's the basis of most neighbour claims - a civil matter between landowners, not a criminal one. See your rights when a neighbour has knotweed.

Wildlife and Countryside Act 1981 (Schedule 9)

The law that makes it an offence to plant Japanese knotweed or cause it to grow in the wild. Note what it doesn't say: having knotweed on your own land is not an offence. See knotweed and the law.

Controlled waste

The legal status of knotweed material (canes, roots, contaminated soil) under the Environmental Protection Act 1990. It can't go in garden bins or ordinary skips - it must go to a licensed facility via a registered waste carrier.

TA6 Property Information Form

The Law Society form sellers complete in England and Wales, which asks directly whether the property is affected by knotweed - Yes, No, or Not known. Answering it wrongly has real consequences: see declaring knotweed when selling.

Misrepresentation

The legal claim a buyer can bring when a seller's answer (for example "No" to the TA6 knotweed question) turns out to be untrue. Damages can cover treatment costs and lost value.

Management plan

A specialist's written, multi-year programme for controlling knotweed on a property - method, schedule, monitoring visits and completion criteria. The document that reassures lenders and buyers.

Insurance-backed guarantee (IBG)

A guarantee on professional treatment that's underwritten by an insurer, so it survives even if the treatment company goes out of business. Most mortgage lenders lending on an affected property want to see one.

Herbicide programme

The most common treatment: systemic herbicide applied to the leaves (or injected) over several growing seasons, translocating down to suppress the rhizome. Needs leaves to work - which is why nothing is sprayed in winter. See how to get rid of knotweed.

Stem injection

Herbicide injected directly into individual canes - used near water, ponds and sensitive planting where spraying isn't appropriate.

Excavation ("dig and dump")

Physically removing the rhizome and affected soil, either off-site to licensed disposal or managed on-site (burial with a membrane, or a bund). Faster than herbicide and available year-round, at a higher price. See what removal costs.

Root barrier membrane

A heavy-duty vertical membrane installed in the ground to block rhizome spreading across a boundary or into a build area - often used alongside treatment on development sites.

Diminution in value

The reduction in a property's market value attributable to knotweed - commonly estimated at around 5-10% depending on severity and treatment status, and often claimed in disputes alongside treatment costs.

PCA / CSJK

The Property Care Association - the UK trade body for invasive weed specialists - and its surveyor qualification, the Certificated Surveyor in Japanese Knotweed. "PCA-accredited with a CSJK surveyor" is the standard lenders and solicitors recognise. Every KnotweediD confirmed report is reviewed by a PCA CSJK accredited surveyor.

Written by Alexander White PCA Certificated Japanese Knotweed Surveyor (CSJK) About our surveyors →

This glossary is general information, not legal advice or a survey. For a property sale, mortgage application or dispute, always obtain a confirmed survey from a PCA-accredited Japanese knotweed specialist.