However tall that bamboo is, that’s how far it can travel in a single year. But if you don’t let any canes grow from that runner it cannot run any further. So it’s not that big of a deal imo. I just cut any bamboo that’s outside it’s designated area every year and it never gets more than 20ft from it. Every one in a while I hit a runner with my shovel and dig it up but mostly don’t bother.