USDA Plant Hardiness Zone Map
Excellent seed planting/transplanting guide from the University of Maine: Maine Vegetable Gardening: Keep Your Garden Growing — Plant from Spring to Fall
Zones 5-6 Planting Schedule
Vegetables that you can grow in Zone 5 include: asparagus, beans, beets, broccoli, cabbage, cantaloupe, carrot, cauliflower, collard, corn, cucumber, eggplant, kale, kohlrabi, lettuce, mustard, okra, onion, peas, peppers, potatoes, radish, spinach, squash, tomato, turnip, and watermelon.
In summertime, wild raspberries, blackberries, and blueberries grow in abundance in Casco.
How to grow wild Maine lowbush blueberry from seed