Cranberries are a unique fruit, known for their tart flavor and their appearance floating in water during the autumn harvest. This fruit is native to North America and grows on low-running, woody vines in specialized environments called bogs. Bogs are characterized by acidic peat soil and a layer of clean sand. The commercial harvest typically occurs between mid-September and early November, when the berries have developed their distinctive deep-red color.
The Internal Air Pockets That Cause Floating
The cranberry’s ability to float is a direct result of its biological structure. Each berry contains four distinct air chambers within its flesh, which act as natural buoyancy aids. These internal air pockets significantly reduce the fruit’s overall density, making the cranberry lighter than water. This low density allows the berries to rise to the surface when submerged, a characteristic central to the most common harvesting method.
The air pockets also serve a biological purpose beyond human harvesting, as they allow the berries to float along rivers and streams to naturally disperse their seeds. Furthermore, the air chambers contribute to the fruit’s physical resilience, giving a fresh cranberry the ability to bounce when dropped onto a hard surface. This natural buoyancy test helps growers separate good fruit from damaged or spoiled berries that have compromised internal structure and would sink.
Wet Harvesting: The Process of Utilizing Buoyancy
Wet harvesting is the most common commercial method and relies entirely on the cranberry’s ability to float. The process begins by flooding the bog with six to eight inches of water above the vines. Growers then introduce specialized machinery, often called water reels or “eggbeaters,” into the flooded bed. These machines feature metal beaters that churn the water, gently knocking the ripe berries from the vine.
Once dislodged, the cranberries float immediately to the surface. The next step involves corralling the floating mass of fruit using large, interlocking barriers called booms. Booms gather the berries into dense, bright-red patches at one end of the bog for efficient collection. The final stage involves removing the berries from the water using a specialized pump or conveyor system that lifts them into transport trucks.
Comparing Wet and Dry Harvesting Methods
Cranberry growers utilize two distinct methods, wet and dry, based primarily on the intended market for the finished product. The wet harvest method accounts for over 90% of the total crop and is used for berries destined for processing into goods like juice, sauce, and dried cranberries. Because the water reel machines cause bruising and the berries are submerged, these cranberries must be cleaned and processed almost immediately.
The remaining crop is collected using the dry harvest method, which is reserved exclusively for fresh fruit sold in grocery stores. This method does not involve flooding the bog and instead uses specialized walk-behind mechanical pickers. These machines operate by combing the berries directly from the vines into burlap bags or boxes.
Dry harvesting is a more laborious and less efficient process than the wet method, but it is necessary because the fruit must be handled gently. Dry-picked cranberries experience less damage and bruising, which maximizes their shelf life and quality for the fresh market. After harvesting, the fruit is subjected to quality control measures, including the bounce test, before packaging.