I was thinking the same thing. Given the small size and looseness of the head, it might be a sprouting variety. That said, I would have expected other heads to be popping up as well. I also wouldn't have expected such a thick central stalk. Maybe just an underdeveloped naturalized version of a regular broccoli or one with poor fertility?
It might be a species of Spigariello/Spigarello. Italian leaf broccoli. It's very good. The leaves are soft and the taste is not bitter like some cole type leaves. I got mine from Johnny's seeds. It does produce small heads but is mainly grown for the leaves.
Or it could be something else. Lots of the brassicas look alike. Do a google image search for Spigariello and see what you think.
Some are more frilly than others. This is what mine look like (though not quite as lush) (photo from the internet)
Location: Germany (Bavaria)
posted 4 years ago
thank you for all your help!!! Of cause it have to be some varity of "Spigarello Broccoli" as you told me. There are a lot of pics and I'm quite sure! Tank you all! Broccoli forever!!!
Don't worry be happy!
Diego Footer on Permaculture Based Homesteads - from the Eat Your Dirt Summit