There are a wide variety of edible greens growing wild in Kythira (and most other places in Greece, and the world), many of them are in the wild dandelion or chicory family.  This video shows some of the tastier types.  There is some etiquette to foraging... when you come across a patch, don't pick it all. Maybe take one of every 3 so that the plant can continue to self seed and grow for future years.