Charlock

Wild Mustard.

Extra: While I was taking the picture Noah saw two deer in the field below and was away... he chased them out of sight over the hill, with no hope of recall. Then he came back. I threw his ball, and when he chased it he put up a hare. And was gone again, out of sight, over the hill... He came back without the ball, tongue hanging out, and had a bit of a lie-down and a drink of water before we went home.