Earlier in the season, I have switched to arugula for cover crop. It's fast growing and I can harvest and sell some, if the rains keep it tasting good. I also believe it helps with fungal issues and diseases that the Music Seed Garlic and Duganski Seed Garlic (both hardneck varieites) can be susceptible to. "Wild" arugula will overwinter here in Southwest Colorado and continue growing in the spring, standard arugula winter kills.
-Dave Banga