Very easy...and do it now before the plant starts shooting this spring. Un-pot it, take a root pruning saw, and saw straight down between the culms. Make sure each section has at least one culm and a reasonable size root ball (too small, and the division may die). When you have your 2-3 pieces, do not do anything to further disturb the dirt or roots; just re-pot each chunk and water well.

Ok Kudzu. I followed your directions and planted the clumps.... three of them in the ground, and one in a pot. Out of the three in the ground, one is doing well, with new green shoots coming up at the base of some of the existing culms. The two others existing leaves are drying out and dying. The clup that I repotted has gone completely dry and looks dead. It's been about three weeks. What do you think?

Well, that should have been a very safe procedure, based on your description. It's hard to diagnose with relatively little info. For the ones that aren't doing well, how big were the root balls that you planted? And have you made sure that all the bamboo have been kept moist? It's pretty clear that the bamboo that are not doing well went into shock, which is not uncommon. That they are losing leaves is not great, but it doesn't mean the plants are dying. Make sure they get plenty of sun and don't dry out. And If you can post some pictures here, I might have a better idea of what the outlook is...

I'm not sure I'd agree with Kudzu about the sun. Since the plants are stressed, I'd keep them shaded for a while until they show signs of improving. You can get some new roots going by watering well with a solution of vitamin B1 or Dyna-Gro K-L-N. If you've still got good leaves, you can also reduce their water requirement by spraying them with an anti-transpirant such as Cloud Cover.

Dave-
You're right. And I should quit answering posts at 2 in the morning!

They do need light, but too much direct sunlight could be (or could have been) a problem. However, since three of them are in the ground, that might be difficult to address.