I've been growing rosso trevisano variety all summer now. They are beautiful glorious plants and quite tasty (bitter but good) So far All i've been able to do with them is cook and eat them as if they were bitter kale. But I really want to get them to form heads! I've searched the internet far and wide and have been completely stumped in my search to find out the technique used to get them to make heads. The closest I got was one Italian newschannel youtube video that I couldn't understand. It seemed like they were digging them out in late fall and placing them somewhere dark. Is that true? I'm really really into this and am up for a project. If there is a way to do this that any of you can advise I'll do it!