Gardeners are being urged to be wary of a unknown mistake that could result in them breaking the law. Homeowners who have Japanese knotweed in their gardens are required to control the non-native plant under the Anti-social Behaviour, Crime and Policing Act 2014.

The plant which forms reddish-purple buds at ground level in the spring, usually grows to around two metres tall and reaches it full height in the late summer. While it was first introduced to the country in the 19th century as a garden plant praised for its ornamental qualities, it is now considered an invasive non-native species.

There are a number of reasons why Japanese knotweeds can cause major issues in gardens. Its quick growth throughout spring and summer results in dense strands of Japanese knotweed that displace other plants, reducing the species diversity.

Japanese knotweed can also cause cracks or weaknesses in hard surfaces, where shoots force their way through and produce uneven surfaces. According to the RHS, Japanese knotweeds can even increase the likelihood of flooding, as the plant can "colonise" river banks, streams and ditches.

The negative impacts have required the plant to be under a number of legal controls. It is an offence to plant or cause Japanese knotweed to grow in the wild under the Wildlife and Countryside Act 1981, Section 14.

Penalties for offences under section 14 include fines of up to £5000, imprisonment for up to six months, or in some cases both. If convicted in a higher court case, the prison time can reach up to two years.

Japanese knotweeds also fall under the Anti-Social Behaviour, Crime and Policing Act 2014. While they are not illegal to have in gardens, homeowners are required to control them and prevent them from becoming an issue in the local area.

For legal action to be taken, the plant must have "a detrimental effect of a persistent or continuing nature on the quality of life of those in the locality". If that is the case, property owners may be prosecuted.

Those selling a property are required to state whether the plant is present through a TA6 form, providing information on where it is and a management plan for its removal.

If buying a property, its presence will be stated on the form, which often results in the mortgage lender requiring assurance that it will be dealt with before the agreement of funds and the purchase is completed.