Japanese knotweed and other garden 'red flags'

Lots of people have heard of Japanese knotweed, but few people know much about it or why it’s a red flag for a property.

When viewing a property, few people give outdoor space more than a cursory look. They’re usually more interested in how much space comes with the property rather than being on the lookout for plants of trees that might be a concern. This guide will explain why Japanese knotweed is bad news for a property and highlight some other common issues to look out for.

In this guide

Japanese knotweed
Why is Japanese knotweed a red flag for a property?
How to get rid of Japanese knotweed
What does Japanese knotweed look like?
Bohemian knotweed
Why is bohemian knotweed a red flag for a property?
What does bohemian knotweek look like?
Bamboo
Why is bamboo a red flag for a property?
What does bamboo look like?
Tree subsidence
Signs of subsidence to look out for

Japanese knotweed

Japanese knotweed is a fast-growing invasive weed. Unfortunately, it is very common in the UK and is considered the area’s most invasive plant.

Why is Japanese knotweed a red flag for a property?

Described by the Environment Agency as “the UK’s most aggressive, destructive and invasive plant”, Japanese knotweed is bad news for your property because of the significant damage it can cause to your home’s structure. Japanese knotweed damage can be so severe that it can make a property unmortgageable.

How to get rid of Japanese knotweed

Mortgage companies may be more willing to consider the property if you have a robust plan for how to get rid of Japanese knotweed.

The weed has very deep roots that are notoriously difficult to get rid of, so it’s important that you hire an experienced professional to manage the removal.

There are several approaches you can take to remove Japanese knotweed. Your main options are:

Herbicide
Digging out
Treatment that combines both approaches

Most reputable companies will offer a guarantee, which means they’ll come back and do further removal work if signs of the weed are spotted within a certain amount of time.

Japanese Knotweed removal cost

The cost of removal will vary depending on the size of the area it’s affecting.

You can expect to pay £1,500-£2,500 for an area of up to 5m², and more than £8,000 for an area of more than 20m².

It is always advisable to hire a professional to remove Japanese knotweed. When looking for a professional to carry out this work, you should look for someone with the following accreditations:

What does Japanese knotweed look like?

The weed has distinctive spade shaped leaves but there are other less damaging weeds that are commonly confused for it. Plants mistaken for Japanese knotweed often include bindweed and giant hogweed. If you’re unsure what it looks like, there are plenty of pictures online to help you identify it. If you think you might have Japanese knotweed in your garden, it’s advisable to contact a professional who will be able to advise you on the best way forward.

Bohemian knotweed

Similar to Japanese knotweed, bohemian knotweed is an invasive weed that has the potential to cause damage to building structures and pipework.

Why is bohemian knotweed a red flag for a property?

Bohemian knotweed spreads very quickly and has the potential to impact the structural integrity of your home.

What does bohemian knotweed look like?

Bohemian knotweed has bamboo-like stems that are round and hollow. They can grow up to 15 feet tall and produce clusters of white flowers.

Bamboo

Is bamboo bad for your garden?

Finding bamboo in a garden can be worrying, but how much of an issue is it?

Bamboo has risen in popularity as a way to create privacy screens in urban gardens, but experts are warning homeowners against introducing the plant to their garden due to its potentially damaging properties.

Why is bamboo a red flag for a property?

Some species of bamboo grow horizontal roots which spread quickly. The roots often grow over 10 metres and can break through brick and concrete. This has the potential to cause significant damage to the structural integrity of your home if the roots get too close to the property.

What does bamboo look like?

Running bamboo, which is the most concerning variety, has rigid and grooved stems. If in doubt, speak to a specialist and ask for advice.

Tree subsidence

Mature trees and plants can be very attractive when viewing a property, both in terms of adding character to a garden and the privacy they often offer.

It is important, however, to be aware of any large trees in close proximity to the house. This is something to be especially aware of it the property sits on clay soil. In certain circumstances, large trees near a property can cause problems with subsidence. This is large trees can take a lot of moisture out of the soil, leading to unstable foundations.

If you’re viewing a property and you spot any large trees in the garden area, it’s worth being extra vigilant for any signs of tree subsidence within the property.

Worst trees for subsidence

The worst trees for causing subsidence are those that consume a large quantity of water. These include oak trees, elm trees and white poplars.

Signs of subsidence to look out for

There are several signs of subsidence to look out for, including cracks and ill-fitting doors and windows. You can read more about what to look for in our subsidence guide.

If you want to sell a property and have concerns about any of the plants in your garden, it is always advisable to get them checked before putting your property on the market. This way, anything worrying can be dealt with and resolved because it causes any problems for your buyer.

Japanese knotweed and other garden ‘red flags’