In article , John Towill
writes
I know that the tops of sprout plants can be eaten like cabbage, but one of
mine has formed a large hard cabbage head on the top. I have never seen
this before, is it unusual?

Sprout tops make very good greens for the kitchen but we have always
waited until the sprouts have been picked before taking them. Your
unusual top growth could be some kind of unintended hybridisation, or it
could be because milder than average autumn temperatures have encouraged
extra growth. Whatever the reason, the greens should be safely edible.
--
Alan & Joan Gould - North Lincs.