Oh yes do contact the garden centers. The people there have been doing things for year and they know the weather in the areas they work, so they would definitely be able to give you advice as to how to work the weather in your area.
I like those paper-plant-holder-thingies. It was just easy to rip the planter open and plant the seedling and leave the pot in the soil. It did take it forever to degrade though. But I just counted that as further food for the plants
