I have planted garlic in freezing temperatures late November and other times when it was so cold your fingers would be numb... we never did anything to warm the soil for planting or afterwards, and there is often no mulch to put on either (especially at the farm) and most times it doesn't affect the crop in any way. Our garlic never breaks ground before winter here, not even when planted first week of October. So don't worry about the garlic, but take care of your fingers - pick a nice day for that.
