Jim Dixon:
I have no idea what a mangelwurzel is. I infer it's something in the same family, but I have never heard them mentioned in the US.

However, I have eaten turnip greens. I rather like greens: kale, turnip, mustard, collard. I buy them in cans.

On holidays in Croatia last year, mangelworzel greens regularly featured on menus. Not a culinary delight to which I hade previously been exposed - but I've known worse!

Regards
p.s. They usually had a spice and a nut chopped through them. Damned if I can remember what...