Knotweed warning post

A gardening warning post has pushed Japanese knotweed back into view, highlighting a plant that can disrupt paving, walls and property sales as well as gardens. (rhs.org.uk) The plant in the post was identified by its accepted name, *Reynoutria japonica*, which the Royal Horticultural Society lists as Japanese knotweed. The species is a tall perennial that can reach about 2.1 metres, with cane-like stems and zig-zag leaves. (rhs.org.uk) Japanese knotweed spreads through rhizomes, the underground stems that send up new shoots, and the UK government says new plants can regrow from rhizome pieces as small as 1 centimetre. The same guidance says owners must stop knotweed on their land from spreading off the property. (gov.uk) The property risk is less about a plant “breaking through concrete” by force than about growth exploiting weak points. The Royal Horticultural Society says knotweed can grow up through joints and cracks in hard surfaces, while Environment Agency guidance includes separate advice on protecting structures, hard surfaces and buried services. (rhs.org.uk, gov.uk) That matters in housing transactions because surveyors and lenders still treat knotweed as a material issue. The Royal Institution of Chartered Surveyors brought in a new residential property standard on March 23, 2022, replacing older distance-based guidance with a management-category system tied to condition, spread and impact. (rics.org, ukfinance.org.uk) Some lenders continue to set explicit conditions when knotweed is found. HSBC UK’s entry in the UK Finance Lenders’ Handbook says it can proceed only if damage to outbuildings, paths and fences is minor when Japanese knotweed is identified within the property boundary. (lendershandbook.ukfinance.org.uk) Control is often slow and expensive because cutting alone can spread the problem. The Royal Horticultural Society says hiring a specialist invasive-weed contractor is often the best option, and government disposal rules treat contaminated soil and plant material as controlled waste in many cases. (rhs.org.uk, gov.uk) The legal backdrop is also stricter than many home gardeners expect. In England and Wales, government guidance says landowners can be prosecuted if invasive non-native plants spread and cause nuisance or damage to other land or property. (gov.uk) Japanese knotweed was introduced to Britain as an ornamental plant and is now listed on Schedule 9 of the Wildlife and Countryside Act 1981, which is why specialist advice focuses on identification, containment and disposal as much as digging or spraying. The latest social-media warning did not change the rules, but it did revive a problem that surveyors, lenders and neighbours have been dealing with for years. (rhs.org.uk, gov.uk)