Or ******* cabbage repistrum rugosum? it is shorter and hairier than my parents are married cabbage brassica olerarea.
As for edible it has a flower with four petals and grows in a rosette, i would at least taste it, but that is just me, I do so at my own risk.
]edit; censor wont allow common name so latin included for clarity
'illegitimate' cabbage has round buds, wild cabbage and wild turnip have long smooth buds, and the other yellow flowered species have long segmented buds.