It's a runner.

What do the mature culms and leaves look like?

Kt

Kentuck,
I have been struggling with this one for many years but I think it might be bissetti. But it's weird be cause is has cold burns on it like a vivax will get. You know the black spots that comes from cold winds when the shoot is young and gets zapped. I thought it was vivax but it doesnt size up like a vivax does and the culms are very thick and strong pretty straight culms too.

Looks like P. Bissetti to me too. I have a couple of groves of bissetti in northern new jersey that look very similar to that. It does get wind burned quite badly without protection, especially near the outside of the groves. What is the average height/diameter of your mature culms? Also, shoot coloration looks mostly like bissetti, but a few more pics couldn't hurt if you have the time.

I have never grown bissetti but have seen groves and photos of it. It does look like bissetti, but I can't be sure from my experience.

How thick are the culms and how tall does the bamboo grow when mature?

Kt

5 years in the ground and this is as big as it has gotten. About 12-15 ft tall and the diameter of the canes is about 3/4 of an inch. The only thing making it seem like it is not bissetti is that it only puts out a few shoots each year. And I thought bissetti put out lots and lots of shoots.

Are there any other unique characteristics about the culms that might help ID it?

Your zone may make the bamboo put up less shoots than say in zone 9.

Kt

If that black cane behind it is the same plant i might guess p. nigra.

There is a cane is the back left of your picture that is starting to look like it's getting darker colored. Also, the bamboo has an ivory band below each node as p. nigra does. Here is a picture of p. nigra shoot a little older than the one you have pictured.

Yeah that is some different divisions. Thats another post.