Calla lilies are tropical bulbs of the genus Zantedeschia which could be considered winter hardy in zone 8-10; your in zone 6b so you would consider calla lilies annuals if left in the ground.  They do make good house plants and/or container plants. You could dig up the rhizomes (bulbs) at the end of the growing season and store over winter to plant the next year.  If planting outside, the first consideration would be soil pH and the best control over this variable would be to pot them in a pot and treat as a container plant.  The other variables to consider are light, bright light with some direct sun during foliage growth, temperature 55-70 degrees when flowering and then 50 - 55 when dormant, and water, moist but not wet so the bulbs do not rot or shrivel and dry out.  You could treat as a container plant on the deck during summer and then treat as a house plant during winter after an period of dormancy.   

Please see attached.