Many (most?) clumping ornamental grasses expand slowly outward, so the newest growth is on the edges and the older growth in the center of the plant. And it is the center growth that tends to die out over time.

Rather than just digging around the edges. leaving only the old center section, it is preferable to take pie shaped wedges as divisions if you don't want to dig up the entire plant. This will leave at least some viable, fresh new growth with the original plant.

That makes sense. I suppose the downside to leaving it in the ground is that the part left behind must be offset from the center to leave a viable plant. I'm about to go out and do some digging.

I saw a demonstration at a large grass garden here in Oklahoma where they cored out the centers of large grasses like you core an apple with a sawzall tool after trimming them down in late winter/early spring. They cored out the whole dead or dying centers and filled the holes with good soil, it went pretty fast. The grass will then put out new vital growth back into the center. They had such a massive number of grasses to deal with that the chore of digging and dividing had become too laborious but once they discovered this less invasive and labor intensive method things got a lot easier. It was cool to watch, that sawzall made short work of it.

I think a sawzall is an excellent tool for this practice regardless of your methods for dividing grasses. I use an old pruning saw and even that is very hard work! It IS a rather labor intensive process :-)

I watched a YouTube video on ornamental grasses and came upon another idea for dividing:. Haven't tried it yet, but here's what was said: Dig half way around the root ball, cut the root ball in half with a Sawzall, refill with garden soil.

Sounds easier than digging it out and dividing,,which I've been doing, but it probably does leave a flat spot on the cut side. Perhaps,there's a way to shape it a bit.