Yes, that is mustard we're seeing already.
It seems to be out early this year, but maybe that is just because it's been so rainy & cold recently. I took these pictures on January 7th.
At one of the vineyards where I take Yogi to chase rabbits, they are in the middle of installing a new trellis system.
Look at all the hardware this new trellising has!
These are the ends of the rows at just one end, and there is a matching set at the other.
Each of the 6 trellis wires will be connected to these ratcheting devices, at each end. This will allow for easy tightening of the trellis wires over the years. Obviously, that convenience comes with a hefty price tag.
The neighboring vineyard shows the vigorous growth capable on the fertile valley floor (can you find Yogi in the picture?). This vineyard is in the process of being pruned.
In the opposite direction is an already pruned vineyard with Mt. St. Helena in the background.