A furniture designer has successfully sued the person he brought a house off after he found Japanese knotweed behind his shed. The seller faces a £200,000 court bill after he denied the plant was growing in the garden. The seller had said ‘no’ on the PA6 property information form when it asked if the property had been affected by knotweed. The presence of Knotweed can have a detrimental effect on the value of a property when you come to sell.