Japanese Knotweed – The Good And The Bad

Japanese knotweed originally introduced into the UK by the victorians to help stabilize the banks of the water features, ponds. lakes and in some cases canals. It was an ideal plant because it established quickly and formed a root system that could hold together even the steepest of soil banks especially where the banks met  the water as the root will happily grow underwater. Japanese knotweed was a fantastic solution to the victorian landscapers and with a number of projects in the UK within a very short space of time had strongholds throughout the UK being transported around to different locations nationwide as it was used in different landscaping schemes.

Then in the late nineties as composting became popular and councils starting to compost large amounts of green material Japanese knotweed increased its hold on the UK spreading further with its seeds often being contained in the compost.

Now Japanese knotweed is a notifiable and controllable weed which is you find any on your land or garden you have a legal obligation to control and eradicate it. Thats not as easy as it sounds

Japanese knotweed (Fallopia japonica) is one of the most talked-about plants in the UK — and for good reason. While it has some surprising benefits, it is widely regarded as one of the most invasive and problematic plants affecting gardens, properties, and landscapes today.

What is Japanese Knotweed?

Japanese knotweed is a fast-growing perennial plant originally introduced from East Asia. It has bamboo-like stems, large heart-shaped leaves, and produces creamy-white flowers in late summer.

It spreads aggressively through underground rhizomes (roots), which can extend several metres horizontally and deep into the soil, making it extremely difficult to eradicate.

The Problem with Japanese Knotweed

1. Highly Invasive Growth

Japanese knotweed grows rapidly and forms dense thickets that suppress surrounding plants, reducing biodiversity and taking over garden spaces.

2. Structural Damage Risk

Its strong root system can exploit cracks in hard surfaces such as paving, walls, and foundations, leading to costly repairs if left unmanaged.

3. Legal Responsibilities

In the UK, it is not illegal to have Japanese knotweed on your property, but you must prevent it from spreading into neighbouring land. Failure to do so can result in legal action.

4. Property Value Impact

The presence of knotweed can affect property sales, with mortgage lenders sometimes refusing loans until the issue is properly treated.

Is There Anything Good About Japanese Knotweed?

Despite its reputation, Japanese knotweed does have some interesting benefits:

1. Wildlife Value (Limited)

The late-season flowers can provide nectar for pollinators when other sources are scarce.

2. Edible Uses

Young shoots can be harvested and eaten, often compared to rhubarb in flavour, and are used in some cuisines.

3. Soil Stabilisation (Historically)

It was originally introduced to help stabilise soil and embankments — although this benefit is now outweighed by its invasive nature.

Controlling Japanese Knotweed

Control is not quick or easy. Key points include:

• Herbicide treatment (e.g. glyphosate-based products) applied repeatedly over several years can be effective
• Do not cut, strim, or move soil containing it, as even small fragments can regrow
• Professional removal is often required for larger infestations using a specialist contractor such as the isle of wight japanese knotweed
• Treatment programmes typically take 2–3 years or more

From our experience at GardenAdvice:

• Small infestations can sometimes be managed with careful, repeated treatment
• Larger areas should be handled by specialists to avoid spreading the problem further

Japanese knotweed is a classic example of a plant that sits between “interesting” and “problematic.” While it has some minor ecological and culinary uses, its aggressive growth and impact on property mean it must be taken seriously.