Agree with all Wintersong says. When I moved here the garden was infested with the stuff, but I dug and amputated and dug again. I very occasionally get the odd wispy bit poking up, and nip the top off as soon as I see it, and get as much root out as I can. However, I do have very light free draining soil, so if you are on heavier stuff then a chemiclal blitz may be a very useful adjunct to the elbow grease approach.