It's a perfect time to divide it, and you don't have to give it another haircut. In fact, the divisions will look better if you don't give it another haircut.

FYI, I'm pretty sure it's a variety of Miscanthus sinensis. That's exactly what mine look like right now, and I'm going to be dividing several of them in the next few weeks.

Below is a link to what it looks like fully grown. Would you say it's probably a Miscanthus sinensis? I try to keep a running list of all my plants, and this grass has always been a blank spot.

As far as giving it a haircut (or not) before splitting -- I totally agree that the small sections will look better when they're re-planted. But if the new green growth proves to be too much and is just in the way, I want to confirm that trimming the green growth now won't have any real negative consequences. I assume not, but I just want to be sure.

Here is a link that might be useful:

Peter..it's definitely Miscanthus sinensis, possibly 'Gracillimus' but I'd have to see a close-up of the leaves to be certain. It's a beautiful clump-o-grass! The narrow-bladed Miscanthus are such graceful plants.

The only negative to giving it another haircut this year is short-lived. The blades you cut will continue to grow, with a square edge on the end. Next year, the new blades will be back to normal.