A gardener who took to social media for advice after spotting an unidentified weed ended up getting bad news. 

The anonymous green-fingered poster sent snaps of the incriminating plant to the r/GardeningUK subreddit asking: 'What is this weed and how do I get rid of it?'

They added: It's coming across from next door and has spread over the front garden over winter.' 

Replies confirmed that it was the dreaded Japanese knotweed - which is expensive to remove, can grow through walls, and can even stop you from getting a mortgage on your home.

One comment said: 'Uh oh, that's the bad one.'

An anonymous gardener asked r/GardeningUK what their invasive plant was (pictured) and sorrowful commenters confirmed it as Japanese knotweed

However, there was a twist - it was actually an undeclared case of the invasive plant in a house which was up for sale

However, there was another twist.

The original Redditer followed up: 'Thanks all. This has confirmed my worst fears.

'I have told a small lie, this is actually at a property for sale, not my garden. We really liked it, but now we're obviously out.

'The estate agent had no idea, but the owner has clearly been cutting it back aggressively.

'The weed has likely [sic] spread from this property to the adjacent ones, as this property is a historic cottage and the infestation covers about 90sq m..! It's very established and under two TPO'd [tree preservation ordered] walnut trees.

'Is there any need to report it now it's been discovered?'

One reply advised reporting it to the local council but others encouraged the poster to not give up on the property. 

A commenter suggested: 'If you like the property don’t let this put you off. Make an offer contingent on the seller buying a 10 year guarantee remediation plan with a certified provider, and lowball. 

'Buyers who are happy to take this on are few and far between and so you are in a great position. Once the seller has a treatment plan in place you can proceed with mortgage etc. 

'Knotweed remediation is super effective. Wait a couple of years before doing any major garden works in the area. The knotweed company will try and sell you nuts ways to do garden works. 

'If you have no regrowth for 12 months crack on with whatever the garden needs. I speak as someone who did exactly this 5 years ago, and got the house we loved for 15k under asking, in a super competitive market cos we were unfazed by the knotweed. It’s all gone now and we wouldn’t need to declare to a buyer.'

Sellers are obliged to declare Japanese knotweed, but you actually can still by a house with it.

The plant tends to devalue properties by around 10 per cent, but can totally destroy a property's value in the worst cases where the plant is closer to buildings and more entrenched.

It can also put off mortgage lenders, so if you do buy a property with knotweed on, ensure that the seller has a plan already in place to remove it. These will tend to include a 10-year insurance-backed guarantee to complete treatment of the weed.

According to Checkatrade, full Japanese knotweed excavation and removal costs an average of £6,500. 

Despite all the legal obligations, it is certainly worth knowing what to look out for when it comes to house hunting and knotweed.

This is particularly important in areas where knotweed is most common, which tends to be all the big cities. Environet have a knotweed heatmap to help with this.

Knotweed is recognisable due to its thick stems, shovel-shaped leaves, red shoots, small white flowers and orange roots.