Could be Rape, could be wild mustard. Need a closer/better picture. Hard to tell the two apart sometimes.
If it is wild Mustard the Deer will eat it after the first frost. Natures anti freeze makes it sweet.
If it is Woad you have real issues. Woad is some bad Mojo.
The farmer recommending you mow it indicates it may be wild Mustard.
Last edited by MudderChuck; 09-30-2015 at 07:56 PM.