When it comes to maintaining ornamental grasses, one
photo says it all:
My rule of thumb: Cutback ornamental
grasses in November, after they have turned completely brown but
before the stems start to break loose and blow around the yard,
making a big mess.
Remedial work: Once new growth has
sprouted (like it has in the early-June photo above) the brown stems
can still be pruned out but they will have to be cut one-by-one, so
as not to damage the new green growth.
Cutback Height: 12 to 18 inches tall
(lower for smaller grasses).
Thanksgiving is a good time to do the job in the midwest and
Exception: If you like seeing the brown plumes over the winter months
(they contrast against the snow) and don't mind the ensuing mess,
cutback the grasses in early spring before new growth begins.