Ideal planting is February - April. Since we get the rhizomes late in their planting cycle, you should plan to get them in to ground pretty quickly. They should be refrigerated in a water misted ziplock bag until they are ready to go into the ground.
You may plant the rhizomes in pots and move them into the ground in June when the ground has warmed. It's a good idea to till the ground you are planting the rhizome into, to loosen the soil and help clear any weeds.