Cranberry beds are ringed by drainage ditches to allow water to drain from beds. Many beds have one of more drainage tile lines running the width of the bed. The water table is manipulated during the growing season to remain 12 to 18 inches below the surface of the bed. Because sites suitable for cranberry production are frequently low lying, frost is a constant threat. Air temperatures below 32 degrees F can damage new growth, flowers and immature fruit.
Water is applied to the cranberry vines through the sprinklers.
As the liquid water changes to ice, heat is released. This heat, called the heat of fusion, is sufficient to protect the vines if the air temperatures do not go too low. Liquid water must be present on the vines at all times or the temperature will quickly drop and the vines or fruit damaged. Frost forecasts are provide twice daily in the spring and fall based on weather observations, satellite imagery and computer modeling. Because cranberries are a perennial crop, they must survive Wisconsin's harsh winters.