Trim away! You won't hurt anything and you can do this any time of the year with any culms you want to get rid of. There is no downside.

Be aware that when you cut any rhizome within your grove, you are dividing one plant into two. This may leave a small specimen within the larger. I'm not saying it's a problem... I'm just saying...

Thanks. That's what I was wondering. Assuming the portions of the plant on both sides of the cut rhizome are well established, will removing the segment of exposed rhizome lead to smaller culms, from either the larger or smaller part of the plants?
What do most growers do? Just leave the exposed rhizomes alone?
Hansel

Hansel-
I simply get rid of anything I don't want...culms and exposed rhizomes. If the rhizomes are putting up culms, they're generally well-established. Cutting off above-ground rhizomes won't hurt any adjacent culms on either side except, perhaps, ones "downstream" of the cut that are really young and have just come up.

When I'm pruning my groves, I often cut above ground rhizomes that are going directions I don't want them to, and I pull out the part of the rhizome just beyond the cut point to make sure I don't get unwanted culms. As tcstoehr points out above, you're dividing the plant in the ground when you simply cut the rhizome.

Don't over-intellectualize this. Prune out what you don't want and don't worry about it. Good luck.