Ornamental grass varieties are a wonderful addition to any landscape. They provide color, texture, beauty and interest the whole year round. Especially when left in tact through late fall and early winter.

Cutting back grasses while they are dormant gives you the opportunity to dig up oversize clumps to divide them into new starts. New starts that will hit the ground growing as soon as spring rolls around!
Cutting back grasses is actually quite simple, especially if you have the right equipment. Although you can cut grasses back by hand with shears, a battery powered reciprocating saw or hedge trimmer will work wonders to speed things up. Electric shears, hedge trimmers and even a chain saw will work as well.
Although grasses can be cut all the way to ground level, leaving a few inches above the ground is best. It not only keeps a bit of interest in the landscape, but gives a nice base for the new shoots to have for support.
How To Divide Clumps To Form New Plants:
When clumps become too large, late winter / early spring is the time to divide to create new plants. Ornamental grasses grow from the inside out. That means new growth will always occur on the outside rings of the clumps, while the center of old clumps dies off.
Begin by digging out the entire root ball of the clump. If it is too large, it can be dug out in sections. The center dead portions can be put directly into the compost pile.

Take a sharp spade to slice through the roots, and then simply replant where needed. As the weather warms in springs, each clump will produce a new plant.
Now it’s time to create new plants! You can create quite a few new starts from an old clump. A sharp shovel or the reciprocating saw makes quick work of splitting them up.
Simply dig a hole for each new clump, and cover around with soil. They do not require any additional soil amending or fertilizers at all. Come spring, they will be ready to grow!
Ornamental grass cuttings are also great to use as focal points in container plantings as well. Simply plant into the center of a big container, and as spring rolls around, it will come to life.
Source: How & Why To Cut Back Ornamental Grasses In Late Winter / Early Spring (oldworldgardenfarms.com)