Empty plot over the winter - to cover or not

Another vote for phacelia!
I bung seeds down as I clear the ground in the autumn and it germinates pretty fast. If the winter is harsh it will die but still cover and protect the soil, if it is mild it'll be flowering by April if not before. And the plants are not too hard to lift and compost when the time comes.
Bees love it.
It is the only green manure I grow as it is easy going!