You may recall a while back we wrote about Japanese Knotweed and how it can seriously affect the structural integrity of your property as well as making it difficult to sell and causing problems with your neighbours. But knotweed isn’t the only bad seed on the block. This week we’re taking a look at 5 invasive species that can seriously devalue your home.

Buying or selling a property is stressful enough without the added stress caused by invasive species growing in your garden! When an unforeseen problem crops up it can potentially disrupt a sale and increase costs whilst you attempt to get it sorted out. This is why it is advisable to take a good look around the garden before you exchange contracts. If you’re not sure what you are looking for, find a friend to help and make sure you let them know how much you appreciate their help if they end up saving the day!

Some invasive species look quite pretty, to the point that you might not realise how potentially damaging they are. This is certainly the case of the first plant on our list, which has very pretty flowers but can cause immeasurable damage and is very hard to get rid of to boot.

Japanese Knotweed

Japanese Knotweed image by Cbaile19, CC0, via Wikimedia Commons

Japanese Knotweed (Fallopia Japonica)

Number one for a reason, Japanese Knotweed is incredibly invasive and also the most difficult to remove. Similar to bamboo, it can grow up to 3 metres (9 feet) tall and its roots can reach 20 metres (60 feet) underground. Which as you can imagine is potentially disastrous for anything underneath your house or adjacent to your property.

Knotweed has been known to destroy pipework and drains, weaken foundations and in extreme cases, it has lead buildings to collapse. And of course, it doesn’t know where your boundaries are, so it will head over into neighbouring properties and merrily weave its way on down the street, causing chaos as it goes. Chaos which – if the plant originated at your place – you are ultimately responsible and liable for.

RICS Homebuyer reports tend to devalue a property by 5–15% if knotweed is found there. You will need professional help to remove the plant as it is incredibly prolific and if even a tiny bit is left it will shoot and regrow from a tiny piece of root or stem.

2. Ivy

Perhaps more surprising on the list as it is so common, Ivy is a native species commonly found growing across Europe and can look quite charming growing around a doorway or covering an old wall, but it can be incredibly damaging.

Ivy will penetrate cracks in walls and masonry, pushing out mortar as it climbs higher and higher, potentially causing damp to seep in through the walls.

There is some good news though, as it is incredibly easy to remove. So before you pop your place on the market you could strip all the Ivy down and it shouldn’t affect the price of your home at all.

However, if you’re looking to buy somewhere that is covered in Ivy, make sure you look underneath to see if it has weakened the walls or caused any damage before you agree to the sale.


Ivy image by Killarnee, CC BY-SA 4.0 <>, via Wikimedia Commons

3. Giant Hogweed

Another non-native invader, Giant Hogweed was brought over from Russia. A relative of our gentle native species, Cow Parsley. Hogweed can cause skin burns and scarring if you get some of the sap on your skin in sunlight.

Typically found near rivers and ponds it can grow up to 10 feet tall and you will find if you have it then buyers may ask you to knock some money off the sale as it can cost up to £15,000 to remove.

Much like Japanese Knotweed, the Giant Hogweed is invasive, fast-spreading and very hard to get rid of.

4. Oak Trees

Although Oak trees do not cause any harm through poisonous sap they can cause problems if they are growing close to your property.

This is because they have a shallow root system which can spread out to 40 metres (120 feet) and if those roots go underneath your property then they will become very difficult to remove once they become established.

They could cause structural problems by cracking foundations, or causing subsidence and other structural defects which can cost thousands of pounds to repair.

And it’s not just Oaks that might cause trouble. Willow and Poplar trees can do the same kind of thing if they are left to grow nearby unchecked.

5. Himalayan Balsam (Impatiens Glandulifera)

As the names suggests, this plant was brought over to the UK from the Himalayas in 1839. A native of the Busy Lizzie, It can grow up to 10 feet tall. It has pretty pink flowers when in bloom but a rather pungent smell and it grows incredibly rapidly, dramatically firing its seeds up to 7 metres when it has finished flowering. Like Giant Hogweed it grows near rivers and often spreads down watercourses.

Authorities such as Exmoor National Park have programs in place to halt the spread of Himalayan Balsam as – like many non-native species – it negatively impacts biodiversity by killing off native plants, stealing their light, nutrients and water and upsetting the local ecosystem.

However although it spread rapidly, it’s not too hard to get rid of. It is incredibly shallow-rooted and easy to pull up so if you’re selling, just make sure you’ve done some thorough weeding before any viewings take place – and if you’re buying a property, check the extent of the invasion and ensure that it is not capable of spreading to a neighbour’s property as this can cause legal issues.

One plant that is often confused with Himalayan Balsam and Knotweed is Himalayan Honeysuckle (Leycesteria Formosa). Although it is also a non-native species it is not known to cause any damage so don’t panic if you find this growing in your garden.

Sorted out all those invasive weeds and ready to make your move? Why not give us a call to see how we can help with a free, no-obligation quote? If you need to store some stuff during the sale or the move, we have secure, stone-built storage facilities right here in the centre of Bridport. We can help you to pack your things and put them straight into storage for you until you’re ready to deal with them, taking all the stress out of moving for you. Give us a call to find out more.

Find more info on non-native invasive plants on the RHS website

Featured Image: Himalayan Balsam by Simplicius, CC BY-SA 3.0 <>, via Wikimedia Commons