Iris tenax

I have a clump of what I believe to be Iris tenax from a plant swap a couple of years ago. http://www.kcis.org/kciseducation/kcissearchingforiristenax.html

This iris is tough and it has overwintered during our coldest winter without even blinking. It appears healthy and is growing. The roots are very fibrous and tough and are all woven together into what is an incredibly dense ball.

The problem for me is that this iris hasn't flowered for me. I suspect that this may be due in part to the fact that it needs more sun. I'll move it soon. But should I divide it? This clump is huge and has probably 100 single plants in it. Is that why it's not blooming? The center hasn't died out, so it's not obvious whether that is the problem.

Also, should I feed it? If so, with what?

Thanks for your help.

Kathy