I assume you are talking about P. nigra. If so. it depends on how large you want it to grow and if you will need to move the pot around.

I would recommend a very large pot. The largest pot that I keep mine in is a 25 gallon pot. The pot doesn't have to be deep, as roots and rhizomes don't go down very far.

It grows about 15 feet in height in the 25 gallon pot as opposed to only 6 feet tall in a three gallon pot. Also, you won't need to water as often in a larger pot.

It grows fairly fast, but you may not see a lot of top growth until the second or third season. I would use a soil that drains well, although black bamboo also does very well in heavy soils. Don't fertilize until it's second season.

Lastly, down here, even a 25 gallon pot will become rootbound fairly quickly, sometimes in only three years. When this happens, divide the rootball into three or more rootballs and replant in more containers.

Good Luck

Kt