Plum Islands grow wild on hard, pebbled bottoms in the waterways and rivers of the Plum Island Sound in Ipswich, Massachusetts. The oysters take 3-4 years to reach market size. Plum Island oysters are unique in apperance. The shells are deep cupped, green, and fluted. The meats are extremely plump with a mild but obvious seaweed flavor. Plum Islands are only available in fall and winter months.