Join Date: Dec 2011
Location: Washington State
Whether or not you blanket has nothing to do with when a horse sheds their coat. The only way to change when your horse sheds is to put/keep them under lights - which means keeping them inside for a certain amount of time each day until the days get longer.
If lights aren't an option, you could always go ahead and have your horse body clipped, in which case you'll need to blanket. Since you're in a colder climate I'd start with a mid-weight blanket and buy others as needed for if/when you're horse is clipped.