Now is a great time to prune ornamental grass. It's not unusual for me to trim some types back again around mid-summer (but well before they begin blooming) to keep them from getting so tall that they collapse. Grass is easy and forgiving!

When I grew pampas grass I pruned it to about 2 ft. each year. I've heard of people burning the clumps to the ground on occasion to control/rejuvenate them, but I never got the courage ;-) Good luck!

Thanks! I was afraid I waited too late.