Sunday, September 7, 2008

Apple #339: Cranberries

Talking to a friend the other day, the subject of cranberry juice and harvesting cranberries came up. We both knew that the berry bushes get flooded with water so that the berries will float, but neither of us knew why. So it's time for your Apple Lady to find out.

Bowl of fresh cranberries
(Photo from the Cape Cod Cranberry Growers' Association)

  • Cranberries grow on low-lying vines, much like strawberries do.
  • The cranberry vines thrive in very acidic soil that is a mixture of peat, sand, gravel, and clay, but mainly peat with a layer of sand on top.
  • Peat, by the way, is spongy, fibrous stuff that is made up of partially decayed dead plants and other organic matter. You can grow other stuff in it, or you can dry it out and burn it.

A hunk of peat. If you wait longer and let this stuff get buried and compressed by more and more layers of peat above it, eventually it will turn into coal.
(Photo from Wyoming Coal)

  • The combination of sand, peat, gravel, and clay occurs in bowl-like wetlands that were scooped out thousands of years ago by the Ice Age glaciers.
  • Most cranberries are grown in the Northeastern US, a few northern Midwest states, and in Canada -- places where the glaciers carved out wetlands with the soil composition that cranberry vines like, and where the growing season is from April to November, which is also what the cranberries like. Some cranberries are also grown in Chile.
  • Of the 1,000+ cranberry growers in the US and Canada, 400 of them are in Massachusetts. So if you want to see a cranberry bog in action, Massachusetts is the best place to go.
  • Cranberries really like water, so growers will give them lots of water at every stage of the growing process.
  • Winter is the dormant period when the vines aren't doing much of anything. But cranberry growers will flood their cranberry bogs during the winter to keep the vines from getting damaged by cold snaps or ice storms or other harmful winter weather.
  • Growers will also clear away bushes and trees that might be growing around the perimeter of the bog. Keeping a space clear all the way around the bog helps to aerate the vines and keeps weeds and bugs and other nasties from getting to the cranberry vines.

Most cranberry bogs also have a ditch around them, which helps keep the water in, and weeds and pests out.
(Photo from the Garden Grapevine)

  • The growers might also lay down some sand on the soil before flooding the bog, if the sand layer is getting too thin. The sand helps keep out the bugs and weeds and fungus that could attack the plants.
  • In the spring, growers will pump the water out of the bogs, fertilize the plants, apply some weed-killer, etc. Sometimes in late spring, the growers might flood the bogs again to control weeds and pests.
  • Here's another way in which water actually helps protect the cranberries: in early spring, when there's still a danger of late frost, the growers will keep a little bit of moisture on the plants as a way to protect them from that possible frost. When the moisture freezes, which happens before the plants would freeze, the freezing process emits heat and keeps the plants warm.
  • So it sounds like, if you're in doubt about your cranberry vines, just give them more water.
  • In late spring, the plants begin to bloom. The blossoms are white or light pink, and the way the petals twist, they look like the head of the crane. This shape is what made Dutch and German settlers call them "crane berries," a name which was later shortened to "cranberries."

Cranberry blossoms, thought to resemble the heads of cranes.
(Photo from the Cranberry Blossom Festival page)

  • During the summer, growers will continue to fend off the weeds and the bugs. Because cranberry vines need one inch of water per week during this part of the growing season, the growers will also sprinkle the vines pretty regularly to supplement rainfall.
  • Growers will also bring in beekeepers to let loose their bees and pollinate the plants.
  • Fall is harvesting time. Cranberries can be harvested one of two ways, dry or wet. In dry harvesting, people push walk-behind harvesting machines that look like oversized, fancy wheelbarrows, which scoop the berries off the vines into boxes.

A walk-behind machine used in dry harvesting cranberries.
(Photo from the Cape Cod Cranberry Growers' Association)

  • Wet harvesting is what you see most often on TV. In fact, 85% of cranberries are harvested this way. The reason lots of cranberries are harvested in water is because the berries have a pocket of air in the fruit, which means they will float.

Cranberries cut open, revealing their magical air pockets
(Photo from medGadget, a medical technology blog)

  • In wet harvesting, the growers flood the bogs with water, and then they use machines called water reels or water beaters that knock the berries off the bushes, and the berries bob to the surface.

A guy named Dave and his water beater, which is "picking" the cranberries off the vines below the water.
(Photo from Royal Ruby Cranberries)

  • Next the growers use things that are floating rope-like tubes, called "booms," to round up the berries into closely-packed areas. From there, the berries are pumped or conveyed up a lift into a truck.

Booms being used to round up the cranberries
(Photo from The Inside Scoop on Farms: Cranberry Bogs)

How the cranberries get from the flooded bog into a truck
(Photo from
Royal Ruby Cranberries)

  • Whether the berries are harvested using wet or dry methods, they are then sorted by color and whether the berries will bounce. If you get a cranberry that doesn't bounce, you know it's spoiled or bruised or damaged.
  • The guy who first discovered this fact about cranberries, by the way, was John "Peg-Leg" Webb. He was a grower who lived in New Jersey back in the day, and because of his wooden leg, he couldn't carry his berries from the loft in his barn where he stored them. So instead of carrying them down the steps with him, he rolled them. He noticed that the fruit that bounced all the way to the bottom was better than the fruit that didn't bounce, and that in fact the fruit that stayed at the top of the steps was rotten or bruised. So that's how he sorted the good berries from the bad, and other growers started bouncing their berries, too.

A cranberry bouncer, used to this day to sort the good cranberries from the not-so-good.
(Photo by kassita on flickr)

  • Dry berries usually go to the fresh markets, meaning that if you buy fresh, bagged cranberries from the store, they've probably been dry harvested.
  • Wet harvested berries are usually turned into juices or the cranberry sauce for your Thanksgiving dinner, or they're used as ingredients in other processed foods.

Cranberry juice which, besides being tart and tasty, is especially good at dislodging bacteria and is thus useful in fighting off infections.
(Photo from

  • Cranberries are one of only three fruits native to North America. The other two are Concord grapes and blueberries -- which are a distant relative of the cranberry.

Cape Cod Cranberry Growers' Association, How Cranberries Grow
The Inside Scoop on Farms, Cranberry Bogs
Royal Ruby Cranberries, Photo Tour: How Cranberries are Grown
Ocean Spray, What's a Bog?
Winston J. Craig, "The cranberry cure," Vibrant Life, May-June 2002


  1. Wouldn't bouncing the berries cause them to get bruised and thereby make them bad berries?

  2. Yeah, I wondered that, too. But apparently the cranberries are hardy little dudes and are not bothered by being bounced down stairs. My guess is that things like bugs and weather and weeds do more damage than the bouncing.

  3. This was SUCH a great article! I just wanted some general knowledge about cranberries, and this was all fantastic. I especially love the descriptions under the photos, eg "Cranberries cut open, revealing their magical air pockets". Thanks so much!

  4. Congratulations on an interesting article. I have to correct the last factoid, however. Assuming that you mean edible fruits excluding things like squashes, there are many more than 3 edible fruits native to North America. For instance, some raspberries, black berries, some currants/gooseberries, thimble berries, salmon berries, squaw berries, many hawthorns (mayhaw), bunch berries, persimmons, pawpaws,red mulberry, several species of plum (chickasaw, hog, wild), strawberries, prickly pear, dewberries, etc. Many of these are commercially grown or collected as well.

  5. Normally I'd say mea culpa and delete the offending pseudo-factoid. But that piece of information comes from the Cranberry Institute, which seems like it also ought to be a trustworthy source. I'm wondering if there's more to that statement than they said. All those other berries you listed have some species that are native to other regions. Maybe the Cranberry Institute meant that these three fruits are the only ones with all varieties native to North America?

    Anybody else care to ring in on this and clarify?

  6. Well, the Cranberry Institute is a group of cranberry growers who are interested in increasing their sales, not in botanically correct information. That three native fruits factiod smacks more of urban myth than real information. They can't mean that the cranberry, blueberry, and concord grape are the only fruits limited to North America in the sense that all varieties are only in North America. The Pawpaw is totally limited to North America. Concord grapes (and muscadine grapes from the South) are both in the same genus as European grapes (yet somehow muscadines are forgotten), and various blueberry species are found in Eurasia. Additionally, cranberries are found in North America and Eurasia.

  7. Great article. This answered all of my questions regarding cranberries and their processing. Thanks for the pictures, too.

  8. Michigan is good for cranberry growing too.


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