Nearly eight out of ten people would be put off buying a property if they discovered there was Japanese knotweed in the garden.
Described by the Environment Agency as 'indisputably the UK's most aggressive, destructive and invasive plant', it spreads rapidly can grow up to 10cm a day.
It's incredibly powerful, and can push its way right through concrete and asphalt - and even destroy homes. Back in 2011, for example, Matthew Jones and Sue Banks in Broxbourne, Hertfordshire were told they would have to knock their house down to get rid of the plant, which had forced its way through the foundations and into the house.
"Attempting to deal with it by cutting it down repeatedly, burning it, burying it or using common weed killers simply won't work as the plant can lie dormant beneath the ground, only to strike again when people least expect it," says Nic Seal, managing director of Environet, which deals with infestations by digging out and sifting the soil.
Many mortgage companies refuse to lend on a house that's got Japanese knotweed nearby. And it isn't the only thing that can blight a house and make it hard to mortgage: here are half a dozen more.
Like Japanese knotweed, Himalayan balsam is an invader from the east, and can grow up to three metres tall. It, too, is very hard to eradicate, meaning many mortgage companies are reluctant to lend.
Many mortgage companies refuse to lend on leasehold properties where the lease has less than 50 years to run. Naturally, these tend to be cheaper - but the buyer will need to come up with cash.
Doubling ground rent
There's been a recent trend for builders to sell homes on a leasehold basis with the ground rent doubling every ten years. While the government may take action, at the moment mortgage companies are unwilling to see their customers commit to such exorbitant terms.
Commercial property nearby
Many lenders reject properties above or next door to shops or other businesses. They reckon that, even if the commercial property is, say, a florist, it could become a smelly takeaway in future, making it harder to sell.
No kitchen or bathroom
Properties without a kitchen or bathroom aren't seen as habitable, and you're unlikely to get the full mortgage. Many lenders, though, will agree to mortgage a property if a swift schedule of works is agreed.
Lenders prefer to stick with what's safe, and are wary of houses built with unusual materials. Concrete prefabs, glass, metal frames and thatched roofs can all ring alarm bells, though shopping around may find one that can help.