Division of clumping potted plants is easy to do – well, relatively so.  Depending upon the kind and size of your bamboo, also the density of the roots, you may need lots of muscle.  In general, remove the bamboo from the pot, cut the rootball into 2 or 4 parts, then report the divisions and perhaps share the extras with friends.   

“How to Divide a Large Potted Bamboo” includes text and illustrations - http://homeguides.sfgate.com/divide-large-potted-bamboo-27564.html  

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