Both. Bamboo is very difficult to remove. The roots spread quickly and far underground. Just when you think you've got rid of it, it will pop up again, usually some distance away, and you start all over again.

A friend gave me some "dwarf bamboo" and I planted it in a border. It took over and became a real menace and took me about 3 years to eventually eradicate it completely using a combination of hard work, regular applications of systemic week killer and an industrial blowtorch.

Good luck.

If those methods do not work you might have to call in a B-52 carpet bombing mission. I'm about ready to do that to rid my garden of the Lysemachia 'firecracker' that I planted a few years ago.

I dug one out a few years back, mine I found quite easy to dig out as the root system was just under the soil, it only took me a week thank goodness, maybe mine wasn't as rampant as some of them :o)).
Look at my Blog (PART 2. Another Revamp) its showing the root system. I was always doing revamps but I'm getting older and finding them harder to do LOL.
Good Luck with yours, hope it's not too hard to get out :o))
It would be nice to see a pic of yours so we can see what your up against :o)
Oh! I made use of the canes in my garden as you will see if you look at my Blog.