That’s because you missed rhizomes, not roots. And if you keep cutting the remnants down after you get the main body of the plant out they’ll starve and die eventually, it just takes a few years.

Speaking as someone who has worked with bamboo for a living for over a decade, an ounce of maintenance is definitely worth a pound of cure. Setting up a proper root-pruning system and cutting the young rhizomes twice a year before they have a chance to spread is much easier than chasing it down after the fact.

Now, tropical timber clumping bamboo… those are tough to deal with once they’re mature. They’re like a boulder that grows lol.