Why not grow it from seed?

Jelitto.com

I grew 288 of them from seed at my last house and planted them on a similar problem area. They ended up OK but showed some variability in height, vigor, blade width, etc. I was hoping to have this site planted with all the same clone and avoid those slight but noticeable variations. If dividing these clumps into individual stems is not feasible, then I will go the seed route. Part of my previous variation problem could have been that the seed I used was harvested by me not purchased, although there were no other grasses in the area and this was an island planting around a commercial building. (The island was in the middle of a river)

You can divide the grass down to a single active growth tip & attached root. The trick is to divide the grass when it is just starting to shoot. A stem does not guarantee a new shoot. Obviously, your best chances will come from divisions made from the outside of your old clump. Take careful note of the planting depth relative to root & stem. Once divided down to individual shoots it is very easy to plant too deeply and that is definitely not good!
a.

good luck!
Personally I find Pennisetums much easier to propagate from seed. Of course that eliminates cultivars or in your case clones of a desirable parent.

Achnatherum, thanks. That's what I was hoping someone would verify for me. I guess what I'll do is divide it up into managable size divisions and then hose it off very well so that I can see where to cut better. I'll try it and see how successful I am. Perhaps I'll leave a good portion of the original plant so that it can recover and make more stems for next year if I don't get enough.

Paul,
I would keep a piece back too - I always err on the side of caution :o)
Once you cut your grass into 4 or 5 pieces you should be able to 'tease' it apart into increasingly smaller pieces. A grower I worked for wouldn't let us 'chop' grasses up from any size - he was always trying to get the most out of every clump. However, my hands are not as strong as they once were so, chopping the clump intto wedges first really works well for me.

Another cavet: try not to let the roots dry out at all while you are making your divisions.

Here are some examples of 1 shoot divisions - not pennisetums .... sorry.

Achnatherum,

Great picture! Now I know exactly what to look for and just have to get the timing right. I think I'll just forget about using the plant in the greenhouse and divide another decent specimen that is still planted in the yard. Spring is probably a better time to do the dividing anyway. Most things I've tried to divide out of the optimum time frame didn't gain me much, if anything, anyway. Good grief, it's still December and I'm already looking for things to plant and seeds to order. I'm going to be a basket case by the time March/April gets here.

just divide it into 10 clumps and divide all of them again next year. That way you'll have better looking clumps that won't "get lost" in your landscape.