Japanese Knotweed- What It Is And How To Deal With It?

What is Japanese knotweed?
Japanese knotweed is a fast-growing, bamboo-like plant originally found in Japan, China, and Taiwan. It was introduced to the UK in the early 19th century because people admired its attractive appearance—gardeners loved how quickly and densely it grew. However, once it spread, it soon became clear that Japanese knotweed was invasive and destructive. These days, it’s widespread across the UK, particularly in London, South Wales, and the South West.

In the UK, Japanese knotweed can grow up between 15cm and 20cm a day. Its roots can burrow down three metres and sprawl out as far as seven metres horizontally. Not only does this make it difficult for other plants to grow, but it can also break through stone, brick, and even some metals.

What does Japanese knotweed look like?
To deal with Japanese knotweed, you first need to know how to spot it. Its leaves are often described as heart-shaped or shovel-shaped, but one reason it’s tricky to identify is that it changes with the seasons:

• Winter: The plant lies dormant, and its stems turn dark brown.
• Spring: The leaves start getting green and shoots are slowly becoming purple. Around April, the new “asparagus-like” shoots appear, and they can grow a couple of centimetres a day.
• Summer: This is when knotweed really takes off—mature plants can grow up to 20cm a day. The leaves becoming larger and the steams are similar to bamboo ones, with small purple specks. By late summer, you might see small cream-coloured flowers.
• Autumn: As temperatures cool, the leaves turn yellow and start to wilt.

If left unchecked, Japanese knotweed can reach up to three metres tall—so size is another major clue.

Why can Japanese knotweed cause to your property?
Knotweed has a reputation for causing serious structural damage. While it can’t literally pierce solid concrete on its own, it takes advantage of tiny cracks and weaknesses, pushing its way in and making gaps bigger as it grows. That’s how it can end up damaging everything from paving stones and tarmac to retaining walls, foundations, and underground pipes.

Aside from causing expensive damage, Japanese knotweed can drastically lower your property’s value. In a notable case featured on the BBC’s The One Show, a couple in Hertfordshire lost £250,000 on their family home due to knotweed issues.

Knotweed removal and disposal is a difficult and costly operation. We at All Junk Removal recently did big house clearance project just outside London. We discovered Japanese knotweed by chance, while doing the job. We had some experience before, dealing with these plans and here is our advice what to do, once discovered: 

Freshly cut stems and roots must be handled like hazardous material to prevent them from taking hold elsewhere, further commented Stan. Meanwhile, chemical treatments can be time-consuming and require repeated applications, since the roots can lie dormant underground. Digging out every scrap of knotweed in your garden or allotment is like embarking on a minor archaeological excavation – you must unearth every last snippet of root to prevent a new invasion.

If you’re in the process of buying a home that has Japanese knotweed, be aware that some mortgage lenders might turn you down until the issue has been treated or controlled. That’s why it’s so important to spot Japanese knotweed early and take steps to get rid of it before it becomes a major (and costly) problem.