Cranberry fields become ponds when it's time to pick

If you walk through a cranberry field in the middle of summer, you'll stay completely dry. These berries don't grow in ponds or underwater, even though every photo you've seen suggests they do. They actually spend their whole lives growing in dry, sandy soil just like any other berry.

The ocean of red fruit only appears because farmers intentionally sink their own fields. Each tiny cranberry has four secret air pockets hidden inside its tart core. Since the fruit is full of air, it wants to float, but the tough vines hold it pinned to the dirt.

Farmers wait until the fruit is ripe, then they pump millions of gallons of water onto the field. Once the plants are submerged, a machine nicknamed a "beater" drives through the flood. It looks like a giant lawnmower with spinning metal loops that whip the water into a frenzy.

This mechanical thrashing knocks the berries loose from the vines. Because of those internal air bubbles, the fruit shoots to the surface like thousands of tiny red corks. The growers then use long floating barriers to corral the berries into a thick, bobbing carpet so they can be vacuumed up.

This water bath is actually quite violent, which is why your Thanksgiving sauce comes from a can. The thrashing and soaking bruises the fruit and washes away the natural waxy coating that keeps it fresh. Because they spoil so fast after a swim, almost every berry you see floating is headed straight to a processing plant to be turned into juice or jam.

If you want to buy a bag of whole, firm cranberries at the grocery store, those berries never went for a swim. They're harvested by "dry picking" with machines that look like motorized combs. It’s much slower and more expensive, but it’s the only way to keep the fruit fresh enough to sit on a shelf.

Even after the harvest is over and the red pond vanishes, the water comes back one last time. In states like Wisconsin, farmers flood the fields again in the dead of winter to let a thick layer of ice freeze over the plants. This frozen roof acts like a thermal blanket, protecting the vines from bitter winds that would otherwise suck the moisture right out of the wood.