How to prevent bamboo from spreading around all of the garden ?

If your bamboo can be dug up and placed in the confines of a large pot, then sink the entire pot in the ground, that will help control the spreading bamboo. Another solution is to dig a trench about 24 inches deep and place a barrier of some kind, like solid wood that the bamboo roots cannot penetrate. Unfortunately, spreading bamboo roots are aggressive and will go deeper than any barricade in it's path. A better solution would be to remove the current bamboo and plant a 'clumping' bamboo that is not invasive and grows wild all over the yard.

Get rid of it and buy the non-spreading clumping bamboo- saves all the hassles, and looks just as effective in a small garden.

I have put my solitary bamboo in the ground in their (black plastic) containers.

Then once a year I give them some extra fertilizer.

And also every year I check for and remove runners that grow over the container edge.

Sorry, once it starts to spread it keeps going.I Recommend removing the main clump. It's still going to spread but not as bad or quickly. All you can do is lop off the shutes as they emerge.

You will need an animal that eats bamboo shoots. You can discover this for your self, or will give you this information later.