You planed the wrong kind of bamboo unless you are planning on shooting a remake of Tarzan. The many types of bamboo fall into two broad categories. The walking kind and the clumping kind. It sounds like you have the walking kind and it will take over your yard. Right up the river from me Thomas Edison was paying the Koreshans to grow various strains (for the light bulb experiments) and we still have good examples of several types. When I stole some shoots for my yard, I was careful to get the clumping kind. They can't control the walking stuff that is still popping up everywhere on the site.