Ask A Master Gardener – Cranberries

Cranberry blossoms, Warrens, Wis, June 21, 2007.  (Photo © Andy Manis)

Cranberry blossoms, Warrens, Wis, June 21, 2007. (Photo © Andy Manis)


What comes to mind when you hear the word cranberry – a small red berry with a tart, tangy flavor, the jellied cranberry sauce served at Thanksgiving, or the Ocean Spray commercials seen on television?

Cranberries (Vaccinium macrocarpon) are a native plant, a “super fruit,” and have a rich history in Wisconsin. Here, commercial production began about 1860 near Berlin, and today many growers are fourth and fifth generation of growers on the same farms.  Wisconsin has the ideal landscape and weather for growing cranberries.  Since 1995 we have been the nation’s leading producer of cranberries, producing nearly sixty percent of the crop.

The cranberry was a staple of Native Americans as early as 1550. Cranberries were eaten fresh, used in cooking, as a preservative, as medicine, and for dyeing fabric.  The Pilgrims learned how to use cranberries from the Native Americans.  The early colonists called the fruit “crane berry,” as the flower of the plant resembled the head and neck of a crane.

Cranberries naturally grow in acid bogs or marshlands, generally an area where no other crop can be grown, the soil pH is usually between 4.0 and 5.5. Cranberry bog soil is unique in that it consists of alternating layers of sand and organic matter.  Cranberries do not grow under water or in standing water, they need a moist but well-drained soil for proper root growth and function.

The cranberry plant is a low-growing, trailing woody evergreen vine that produces stems or runners from one to six feet long. The leaves are tiny and oblong in shape.  In Wisconsin, cranberries flower in late June and early July.  Berries start to develop after pollination and will change in color from green, to white, to dark red at maturity.

Cranberries are self-fruitful, meaning the pollen from a flower can pollinate itself. Insects, such as native flies, bumble bees and wild bees do the task of pollination.  Many farmers also hire beekeepers to bring hives of honeybees to the fields to help with pollination.  Scientist at UW-Madison have been testing whether planting wildflowers around cranberry fields will help attract native bees to improve pollination and crop yield.

Cranberry pests include several insects that attack the fruit or vines of the plant, fungal diseases, and weeds. Pests can reduce yields and fruit quality. Cranberry growers follow the principles of Integrated Pest Management (IPM), monitoring pest activity and controlling pests when necessary.

Water is used to protect the plants in the winter.  Bogs are covered with water that freezes, the ice layer protects the vines from extreme cold and fluctuating temperatures.  Sprinkler systems or flooding provide water to protect the buds and berries from frost, control pests, and help in the harvesting process.


Cranberries are harvested in the fall – generally mid-September through mid-November. There are two ways of harvesting – dry and wet.  Fresh fruit growers use the dry method.  This method requires hand picking or the use of mechanical pickers to remove the berries from the vines.  Wet harvesting is used with cranberries that will be used for juice, sauce or sweetened dried cranberries.  It’s the most common and cost effective practice.  In this process the bog is flooded with water and special equipment is used to churn and loosen the cranberries from the vine.  Cranberries have small air pockets that allow them to float to the surface, making it easier to scoop them up.

Cranberries help maintain a healthy heart, help support memory, and a healthy immune system. They do this by being a good source of Vitamin C and fiber.  They are fat-free, cholesterol-free, low-calorie, and low in sodium and are the highest of all fruits in antioxidants.

Cranberries can be grown in the home garden, (bog not required) as either an ornamental plant or an edible ground cover. A separate bed may be required as cranberries require sandy, acidic soil.  The top six to eight inches of soil would need to be replaced with a mixture of peat moss and sand.  The University of Maine Cooperative Extension ( has information on successfully growing cranberries in the home garden.

cranberry-picIn case you are wondering, jellied cranberry sauce has been around since 1930 and contains 200 cranberries per can. It was Ocean Spray’s first product, and was produced to extend the selling season of cranberries.  Fresh cranberries had a short selling period; canning the cranberries made them available year-round.  Ocean Spray was started in 1930 by three cranberry growers.  Today, Ocean Spray cooperative has grown to more than 700 grower families across North America.

Christea Jacobs

UW-Extension Certified Master Gardener

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