I harvest mine when the heads are cascading and are a rich "ruby" color. Grab the grass 4-6 inches from the ground -I do a hand full at a time- and cut. I then take the grass by the neck and shake to remove any blades of grass that are not attached. I then rubberband and put in a bucket of water. The grass should give you a second harvest not as tall as the first but useable. If you have waited too long and the heads are a dull brownish color, I would cut it back and wait for the second harvest to use it.

Patty

Thanks Patty! I should have listened to my wife's advice! Do you have any problems with the grass falling over after it gets a certain height? I came back to my field after a heavy rain and my entire patch of grass was flattened and it wasn't a pretty sight!

Yes that is a problem. Last year that happened to me. It was at harvesting stage though, and I had it in landscape fabric (no dirt on the heads) so I was able to cut and use it. I should have used support netting.
Patty

Glad I found this thread...I just collected some seeds from mine and wondered if I could cut it back for a second flowering....

I sooo hate to cut it off just yet as it is peaking at the moment...how long do you think I have?