Transplanting involves digging a large chunk of root ball out of the ground with the culms attached. Try not to transplant bamboo when it is shooting. Dig bamboo either very early in the spring before there’s any chance of shooting or wait for the growth period to be over late in the autumn. You should look for a clump of culms that has come up in the last year or so and which includes at least three or four healthy-looking culms.
A good size for the clump would be at least two feet in diameter unless you are potting, then under 18" in diameter. Bamboo rhizomes are tough but must not be allowed to dry out even for a few minutes. You may have to use a very sharp shovel, ax or saw to separate the rhizomes and roots from the rest of the grove.
If you will be transferring the division by truck, then water the leaves and roots well, wrap the whole rhizome clump in burlap and get it into the ground as quickly as possible.