Now is the best time, don't mulch if you are planting straight away as the frost is essential for making the sugars/starch in the plant evolve to make for a better crop. Mulch it when it starts shooting to protect the stalks from late frosts, some say that frosted stalks are poisonous, but as you can freeze the stuff it does seem a bit far fetched. An old trick was to force it on when it started shooting with an old bucket put over the crown. You probably knew that anyway.