Zebra grass

if the foliage still looks good i'd leave it alone. If there are dead bits cut them out.
welcome to GoY by the way.

Im in the south and I usually do mine as late as possible. If it looks OK leave it until it doesnt....

Most grasses are best deal with by "combing" rather than cutting back. The dead bits should come out quite easily.

Alice, that's the evergreen ones - this one is deciduous, so as Milky said - leave the dead stems on it for winter interest, then cut it to the ground in very early spring, before the new shoots appear.

All the stems will die right back as it's a Miscanthus.

ditto to Spritz, with early spring being February to early March

I have a very tall deciduous grass (5ft) that's got scutch grass amongst it so I'm hoping to spray it when it 's dormant. Not sure what 'Zebra grass is but I agree, leave until it starts to look shabby.

zebra grass is a common name used to describe the horizontal banded forms of Miscanthus sinensis, of which the two most often seen are Miscanthus sinensis 'Zebrinus' and 'Strictus'