Mache is the sweetest, most tender salad green and we harvest it all winter and fall. It's one of the few non-bitter greens I've been able to grow in this climate that survive our droughty weather and my inconsistent watering. One warning, though -- it takes forever to sprout and many times I've given up on it, planted something else in its place only to have it finally sprout around the edges of my other plantings. This batch was hiding under the huge leaves of an artichoke plant.
By the way, the last time I checked, mache was about seven or eight dollars for two ounces in a plastic clam shell box at Whole Paycheck, err, I mean, Whole Foods.