When And How Do I Trim Ornamental Grasses?

Anytime from February to early April is the time to cut back your ornamental grasses.  Some gardeners like to cut them back in late fall because the snow will smash them down, leaving them untidy.  I, however, think the dormant grasses look interesting in the winter with snow and frost on them.  I wait until spring to cut them down.  Then, the best thing to do is to cut them down as short as you can, any way you can.  I use hand pruners and cut off handfuls at a time.  You can use hedge trimmers, power trimmers or a sawzall.  The cool season grasses (Festuca, Calamagrostis(Karl Foerster Grass) and Helictotricon(Blue Oat Grass) will start growing in April, so they need to be trimmed before then.  The warm season grasses, like Miscanthus and Panicum virgatum will start growing in late April and May, but cut them back now so they are ready.

Festuca mairei - on the left, before trimming - on the right, after trimming