I can't tell the difference between mine, and they are both mature clumps.

This is the reason that I believe that mine are one and the same plant. According to the ABS website, Oldhamii is more erect and has longer internodes, whereas the Beechyana has shorter internodes and the culms arch outward.

Mine are both tight clumpers with similar branches and leaf size, and have very erect growth habits.

When small, many bamboos resemble others very closely, so don't mix up the labels on the plants.

Kt

Am getting some oldhamii next spring . . . at least that's what I hope it will be.

I have heard, though, that some bamboo at the New Orleans zoo (in the South America exhibit) is oldhamii. There, it is definitely not in tight clumps; there's enough room between culms to walk through and feel like it's a bamboo grove. The one unknown that I can't account for is how much this "grove" is groomed to maintain spacing between the culms.

That's my half-a-cent worth.

Dave