Rule 1: Black bamboo is like any other bamboo.

Rule 2: Prune out whatever you don't want, whenever you want.

Rule 3: Whatever you prune out will not regenerate.

Rule 4: Whatever you prune out will not hurt future growth.

Kudzu: I disagree with Rule 4. Take the extreme case of cutting down *every* existing culm. Will that hurt future growth? Yes, it will set the plant back a bit, maybe a few years or more. New culms will be smaller. So there must be some limit to the number of culms you can remove without affecting next year's culms... I believe I've heard 30%. That is, you can remove about a third of the existing culms from an established grove and not set it back.

Does that sound right?

alan-
Yes, I agree that clearcutting a bamboo would not be good. The "rules" I was providing were specifically for the OP in the context of the particular issue posed, given that he/she seemed overly hesitant. In a healthy, established bamboo I routinely take out all small stuff, all whip shoots, and all larger culms that look like they are starting to near the end of their useful lives (losing color and having significantly diminished foliage). In a healthy plant this will not affect future growth and may help it...and it won't be that big a proportion of the clump.

Thanks everyone.

So the weird culms that don't come up vertically are whip shoots? Cool, now I know.

smasraum-
Yes, that's correct. I get them every once in a while, even on older clumps. An alternative to either leaving them alone or pruning them out is to bend them up to a vertical position when they are about a foot long and hold them in place with twine attached to another culm. Once it gets to its full height and hardens off, it should stay vertical after the twine is removed.

Good to know, I'll remember that. Actually, I was out pruning earlier, and I think I remember seeing a new whip shoot that I may have to introduce to a little bondage. I'll just tell it "it builds character". :o)