I agree with what Claudia has said; removing knotweed stem growth (by whatever method) will leave you in a mess, or the next owners of your property. Property vendors should bear in mind that they are obliged by law to declare the presence of knotweed on the property, even if it's no longer visible. It's worth mentioning that someone who knowingly covers up the existence of Japanese knotweed is likely to find a solicitor's letter on their door mat at some point in the future, claiming for the cost of treatments and guarantees. On another note, there's also a factual error in the text; Japanese knotweed does go to seed but the seeds are infertile as we only have male plants in 'the wild' in the UK. I wonder where we'd be if we had female knotweed plants here too... Trueglory, this is probably way too late, but yes, and contact a specialist who carries the proper accreditations to excavate and remove it.