'We stretched our budget to buy dream home - only to discover the Japanese knotweed problem'

'We stretched our budget to buy dream home - only to discover the Japanese knotweed problem' Japanese knotweed spreads underground, so Nathan Hannaway and his family had no idea the garden of their fantastic new home was infested by the aggressive and invasive plant A couple who splashed out on an incredible five-bedroom Victorian home had to put their renovation plans on hold after discovering a hidden Japanese knotweed infestation - costing them a further £15,000. Nathan Hannaway and his partner spent £430,000 on the property in the affluent suburb but later found five shoots of the weed in the back garden. This invasive fast-growing weed takes over gardens and can be incredibly difficult to remove as it chokes other plants. It can block light, tears apart fences, sheds and brickwork and cause homeowners choas as it can easily remain undetected until it escalates into a more serious issue. It spreads through an underground network of roots and can wreak havoc on gardens, property values and house sales but some areas suffer more than others. Nathan and his partner have had to spend £15,000 to remove the Japanese knotweed. They had moved from a two-bedroom house in Bury, Greater Manchester, to the address in Whitehall, near Blackburn, Lancashire, and hoped to transform its overgrown garden while creating more space to expand their family. But they became aware of the weed soon after moving in. Nathan, 33, said: "I was quoted £15,000 to remove it - I was shocked. What they found when they excavated was unbelievable. There was so much of it. "When we heard it would be £15,000 to remove - that was a big chunk of our budget for the renovation. Everything I wanted to do with the garden is now on hold." The father of two, who runs a wind-turbine testing company, had initially barely heard of it - so researched its red-speckled stems and walked along nearby riverbanks to see what it looked like. A survey by Environet found knotweed growing in three separate areas of his new home. Nathan was not aware he and his family had moved to the UK's worst postcode for Japanese knotweed. New data shows Whitehall, the small neighbourhood in Darwen, Lancashire, with a population of 9,000, has the highest number of recorded infestations in the country. A total of 92 incidences were logged in BB3 2, which sits in Blackburn with Darwen - itself named Britain's worst-affected borough with 2,135 cases, or 40 per square mile - in figures compiled by leading invasive-plant specialist Environet. Nathan's neighbour Brian Hartley, 84, said he had seen knotweed appear in his garden during the 30 years he has lived there. He said: "If you don't stay on top of it, it spreads like wildfire." Nearby at Blackburn Old Cemetery, fresh clumps have also been cordoned off to stop lawnmowers slicing the plant into fragments and spreading it across the grounds. Maurice Ffelan, 82, of the Friends of Blackburn Old Cemetery, said: "It's a bugger to get rid of. It can grow to 10ft tall." It can also grow up to 10cm a day in the summer heat, reaching up to three metres across a single season. Volunteers injects glyphosate weedkiller into mature stems in an attempt to kill the dense underground root system. Maurice added: "The problem is if you start mowing it, you transfer little bits about and you don't notice until the next year when it suddenly starts popping up everywhere." Guidance from Propertymark, the professional body for estate agents, says knotweed is material information which should be disclosed and warns it can reduce prices, delay transactions and cause sales to collapse. UK's knotweed hotspots Blackburn with Darwen - 2,135 incidences; 40.36 per sq mile Bristol - 1,323; 31.5 per sq mile Bolton - 1,651; 30.59 per sq mile Brent - 464; 27.8 per sq mile St Helens - 1,324; 25.15 per sq mile Cardiff - 1,208; 20.94 per sq mile Newport - 1,752; 20.86 per sq mile Haringey - 236; 20.65 per sq mile Lambeth - 204; 19.39 per sq mile Nottingham - 528; 18.23 per sq mile