Is this a case of nasty knotweed?
Q Is this Japanese knotweed? PAUL ADAMS, GREATER LONDON
A I’m afraid the plant in your photo is the pernicious Japanese knotweed. However, it is possible to control and kill it, with perseverance. If the clump isn’t huge, it can be dug out. After digging up the roots, shake off the soil and either place them on a gravel or concrete surface so they dry out completely and die. Or, put smaller pieces in a large container of water to rot. Then they can be composted or added to the green waste bin. You can spray plants with a glyphosate-based weedkiller, or cut the stems to about 60cm (2ft) high and pour the dilute weedkiller into the hollow
stems at this time of year. This will greatly reduce regrowth next year but you’ll have to apply the weedkiller several times to get rid of the plant altogether.