Peas that have been canned or frozen are vastly inferior to a freshly harvested springtime pea. They might as well be completely unrelated vegetables. When people first try the fresh ones, they usually say something like, "These are the best peas I've ever tasted in my entire life."
Now's the time for your own pea-k experience. According to Jesus Muñoz of Glendale's Crooked Sky Farms, once the peas mature on the vine, they must be harvested quickly, and then the vine dies -- that's why their appearances in markets are rare and brief. Crooked Sky grows three varieties of field pea, and the first one to mature, the English pea, is hitting market stalls now.
Although you can eat the entire pod uncooked or cooked (raw, it's a lot like a snow pea or a sugar snap pea), it's best enjoyed before the peas inside get big and the outer pod becomes tough and sad-looking -- at that point, it's better to shell and cook the peas. If you don't have livestock to feed, throw the empty pods on the compost pile.
Crooked Sky maintains stalls at Ahwatukee Farmers' Market on Sunday and Downtown Phoenix and Roadrunner Park markets on Saturday.
Peas be with you!