While no one has ever said to me "Nice dandelions. We should make a salad," it's comforting to know that some of the growing things in Chicago forests are edible. North Park Nature Center (near Pulaski and Peterson) is hosting its City Wilds Festival this weekend, with a native plant sale and a crash course on native plants that are edible. Also includes live animals, composting, children's music and probably a grand old time.