Cranberries are a unique North American fruit, native to wetlands, and their cultivation relies on a specialized environment known as a bog. The cranberry plant is a perennial, low-lying vine. The majority of the commercial supply comes from Wisconsin, Massachusetts, New Jersey, Oregon, and Washington, regions that provide the necessary combination of sandy soil, abundant fresh water, and a cold winter dormancy period. Cranberry vines do not grow underwater, but constructed bogs allow growers precise control over water levels for protection and harvesting.
Establishing the Cranberry Bog
Creating a cranberry bog requires significant initial land preparation to ensure proper water management and vine health. The ideal location features a fresh water source and naturally acidic soil, with a preferred pH between 4.5 and 5.5. Growers prepare the land by grading it meticulously to create a flat, level surface, which is essential for uniform flooding and drainage. This process often involves layering the bed with sand, peat, and gravel to replicate the natural wetland environment.
Beneath these layers, a firm base of clay or an impermeable layer prevents water from leaching into the groundwater, turning the bog into an effective reservoir. Extensive drainage and irrigation systems, including ditches and sprinklers, are installed before planting to allow for rapid water movement. Cranberries are typically planted using pre-rooted cuttings or by spreading pruned vines from established bogs across the new bed. These vines are then pressed into the sand, where they root and form the dense mat necessary for future harvests.
Year-Round Management of the Vines
Once established, the crop’s success depends on careful, year-round maintenance of the perennial vines. One distinctive practice is sanding, where a thin layer of sand (1/2 to 2 inches thick) is applied to the bog surface every few years. This periodic sanding encourages horizontal runners to root, stimulating the growth of new upright, fruit-bearing stems, which functions as a pruning mechanism. Sanding also helps control pests and weeds by burying seeds and insect eggs, improves drainage, and promotes nutrient release in the acidic peat soil.
Water management is a continuous effort throughout the non-harvest growing season. Sprinkler systems are used for regular irrigation to maintain soil moisture, which is important given the cranberry vine’s underdeveloped root system. The sprinklers are also used for frost protection during the spring and fall shoulder seasons. When temperatures drop toward freezing, water is applied through the sprinklers, and as it freezes, it releases latent heat that protects the sensitive buds and berries from damage.
Growers must also actively manage pests, diseases, and the dense growth of the vines. A heavy canopy of vines can accumulate, requiring occasional mechanical pruning to maintain productivity. In the late fall, after the harvest, the bogs are flooded deeply, and this water remains on the vines throughout the winter, often freezing over. This winter flood protects the dormant vines and buds from the extreme cold temperatures and harsh winds.
Harvesting the Crop
The cranberry harvest occurs annually from mid-September through early November, and the method used depends on the intended market for the fruit. The vast majority of cranberries, over 90%, are gathered using the wet harvest method, which is used for berries destined for juice, sauces, and other processed goods. This process begins when the bog is flooded with up to 18 inches of water, usually the night before the harvest.
Specialized harvesting machines, sometimes nicknamed “egg-beaters” or water reels, are driven through the flooded beds to gently agitate the water and dislodge the berries from the vines. Cranberries float because they contain small air pockets inside the fruit. Once detached, the berries rise to the surface of the water, where they are corralled using wooden or plastic booms. They are then loaded by conveyor or pumped directly into trucks for transport to a receiving station.
A smaller portion of the crop is collected using the dry harvest method, which is used for fresh fruit sold in grocery stores. Dry harvesting utilizes specialized walk-behind machines that comb the berries off the vines into burlap bags. This method is gentler on the fruit, resulting in less bruising and a longer shelf life necessary for fresh consumption.