The Peaberry Bean
If you've been at the coffee game for a while you might have come across a "Peaberry" coffee. But, what is it? It's a description, not a legend, not a flavor, and certainly not a pea.
As the coffee plant matures it begins to grow "cherries" which produce two coffee seeds (beans) per cherry...usually. Every now and then a plant will produce cherries which produce a single seed (a peaberry) which is visually indistinguishable from the classic cherry anatomy and morphology.
Due to the difficulty of determining which cherries will produce a single bean, the peaberry is discovered during coffee processing (extraction of beans form the cherry). The main differences being in size and shape as the peaberry is rounder (like a pea) and just slightly smaller than a conventional coffee bean.
Due to the rarity and increased labor in separating peaberry from normal coffee seeds these beans have quite the price difference in comparison to regular coffee. There are a few countries that tend to produce more peaberry beans than others including Kenya, Tanzania, and Hawaii (Kona variety) but any coffee plant can produce these beans spontaneously.
Flavor and Roasting
There are those who theorize peaberries are sweeter and fruitier due to the high energy involved by the mother plant in producing one single bean in the cherry amplifying the intensity of their flavor. As far as roasting, a peaberry coffee beans require special attention due to their size and shape to secure an even heat distribution.