Michelmores LLP
Posted on 5 Jul 2021
By Michelmores LLP

What is Japanese Knotweed and why is it a property sale/lease problem?

For those considering the sale or lease of property, or even share sales, Japanese Knotweed is a concept that comes up in pre-contract enquiries and other contractual documentation. We consider what it is, how to identify it, and why this is important.

What is Japanese Knotweed?

The warmer weather – along with the gradual easing of lockdown restrictions – has encouraged more people to spend more time outside. It also creates a welcoming environment for Japanese Knotweed. This is a type of perennial weed, identified by its reddish-purple shoots, thick green asparagus or bamboo-like stems, green matt spade-shaped leaves, and eventually small white/cream flowers.

Why is Japanese Knotweed a problem?

The weed starts to appear in late Spring and grows rapidly, before dying back to ground level in the winter. Its swift growth timescale contrasts with its timely and potentially costly eradication. This is because, unlike common weeds, it is a non-native invasive species with a destructive nature. It is notorious for diminishing the value of properties, causing significant damage, and harming biodiversity.

Is Japanese Knotweed illegal?

It is not illegal to have the weed present on premises, but growing or allowing it to spread onto anyone else's property can risk an abatement notice, nuisance order, or community protection notice. Homeowners can also be the subject of a common-law nuisance claim regardless of whether the weed has caused any physical damage. There is also a risk for company directors, as they risk personal criminal responsibility if their company sells a product contaminated with Japanese Knotweed.

How can Japanese Knotweed be eradicated?

Japanese Knotweed is classed as ‘controlled waste’. As a result, there are strict controls over its eradication and there is a risk of criminal penalties if the weed is improperly disposed of. Professional treatments are therefore generally favoured in particular as they can provide warranties or specific indemnities to prevent lessees inheriting responsibility for the weed, and insurance-backed guarantees which are often required by lenders on a purchase affected by Japanese Knotweed. Given the significant risks it entails, identifying and treating Japanese Knotweed at an early stage is vital.