Peas are at their peak when spring turns to summer but before the days are truly hot. According to Farmer Lee Jones of The Chef’s Garden, Huron, Ohio, even half a day of hot sun can speed the conversion of sugar to starch in peas, both on the vine and off. In hot conditions, farmers sometimes shell peas to keep them from overheating in the pod, which can act as an incubator. Whether you’re buying peas shelled or in their pods, the important thing is to get a taste to ensure that they’re sweet; at a farmers’ market you can usually ask for a sample. If buying in the pod, you’ll need about a pound for a cup of peas.