Hi saddad,
Not sure which variety you are talking about, but I grow these two,"Osaka Purple " Mustard Greens for cooking & Giant Miike mustard greens
from the real seed company, they grow right through the winter with no protection, I have some enviromesh over them just to stop the flying rats.
They have a hot mustardy flavour when raw but when they are steamed (like spinach) they are very tasty ;D
Adrian.