The answer to that question is obviousy it depends where you are living. Different areas, referred to as zones, are prone to different tpes of vegitation. Hobby gardners and serious farms alike have turned to the Farmers Almanac for decades on guidance to the best planting days. You can locate your zone, long range weather forecasts and the best planting days at
http://www.farmersalmanac.com. After consulting the almanac I went to my garden to do some preperation for the spring. I came across three plants that had obviously germinated from last seasons planting. I wasn't surprised since the winter has been mild.