There are also a lot of knowledgeable people at the GardenWeb Bamboo forum GardenWeb Bamboo Forum

If your bamboo gets enough water and food, the roots will probably break through the sides of your Rubbermaid containers. Vertical sides for a bamboo container are not advised.

The most desirable way to keep bamboo confined is to dig a trench about two feet deep, beveling the sides inward as you dig down: \__/ and line them with heavy flexible pond liner material (don't worry about the bottom). Bamboo roots travel horizontally and seem to exert a lot of force when confined. The angled side allows the roots to hit the barrier and then deflect them upward, where they are visible. Routine inspection of the perimeter allows you to see when roots are projecting upward and you can lop them off.

Sue