It’s one of the rarest types of coffee. Connoisseurs treasure it for its delicacy. And it is neither a pea nor a berry. So, exactly, what is a peaberry?

To understand, you first need to know how coffee grows. Coffee beans grow within fruits called cherries; when ripe, they turn a vibrant red. Most of the time, the cherry contains two seeds that grow side-by-side. These are typical coffee beans. Growing together within the fruit, they develop that shape that you’re familiar with, with a flat side and a domed side.

About 5-10% of the time, however, only one seed grows within the cherry, possibly due to only one ovule being pollinated. These single beans are called peaberries. (Yes, if you’re curious, it is also possible for three berries to mature in a cherry, though that is even rarer.)

How Are Peaberries Different from Other Coffee Beans?

Because peaberries have the cherry all to themselves, they are shorter, plumper, and rounder than their twinned brethren. Since they are sized and shaped differently from regular beans, they require different roasting techniques, and so they must be sorted and separated. However, all but the most practiced can’t tell from looking whether a cherry is concealing a peaberry or a normal pair of beans. This becomes apparent only after the cherries are processed and dried. Growers use sieves, or sometimes more sophisticated machinery that sorts by weight and size, to differentiate peaberries from the rest of the beans.

Peaberries are not intrinsically superior to other beans, just different. They can appear in all growing regions around the world. The same factors that influence the quality of regular coffee beans, from terroir to processing method to transportation and roasting, affect peaberries in the same way.

Do Peaberries Taste Better than Regular Coffee Beans?

Devotees of peaberries swear that they impart bright acidity, sweetness, and more complex flavors than their counterparts. Some theorize that the peaberries benefit from not having to share nutrients with a sibling bean during maturation and therefore have more flavor, but there is not actual evidence for this.

Any difference in flavor may be a factor of the way they’re roasted. Since they are rounder, they roll more easily in the roaster, making heat transfer more efficient. On the one hand, this means that first crack can come earlier and at a lower temperature than with regular beans, but since they are plumper, it can take longer for heat to penetrate to the center of the bean. Great attention to detail is required so as not to scorch the peaberries.

Why Are Peaberries More Expensive?

Since peaberries occur only in about 5-10% of coffee cherries, they are relatively rare. They must also be sorted and separated, which is usually done by hand. Add to that the mystique and perception that they have a uniquely complex flavor, and peaberries have a cachet that puts them in a class of their own. For these reasons, coffee connoisseurs are happy to pay a premium for these special beans.