What Are Coffee Beans? A Guide to Green Coffee

Ever wonder what’s really inside that bag of green coffee you bought online? Most people picture coffee as dark roasted beans ready for brewing—but long before roasting, there's the raw seed, pulled from a fruit most have never seen. That’s what we’re unpacking here: the actual form of the coffee you eventually drink, how it grows, and why some look different than others.

Coffee ‘beans’ are the seeds found inside coffee cherries, usually two flat, oval seeds per fruit. In about 5% of cherries, only one rounded seed develops—this is called a peaberry. These seeds, often mistaken for beans due to their shape, contain rich endosperm and are the true starting point of all brewed coffee.

What Exactly Is a Coffee Bean?

Despite the common name, the ‘beans’ used to make coffee aren’t beans at all—they are seeds. Specifically, they are the seeds of the coffee cherry (also known as the coffee berry), the fruit produced by coffee plants. Each cherry typically holds two seeds that are flat and oval in shape, lying against each other. However, in a small number of cherries—around 5%—only one seed forms. This lone, rounded seed is known as a peaberry. Though they look like beans and are commonly called beans, they are the true botanical seeds of the coffee plant, containing the embryo and nutrient-rich endosperm needed for growth.

Where Do Coffee Seeds Come From?

Coffee seeds originate inside coffee cherries, the fruit of the coffee plant. Each cherry normally contains two seeds, but occasionally a cherry will develop just a single, rounded seed (peaberry). These seeds are harvested, processed, and dried to become the green coffee beans used by roasters. The familiar flat, oval shape comes from the seeds pressing against each other inside the cherry. Only after roasting do we see the brown ‘beans’ used in brewing.

The Origins and Early Spread of Coffee

The journey of coffee seeds began in Ethiopia around the year 850 CE. Historical accounts suggest that coffee cultivation and consumption started in this region before spreading across the Arabian Peninsula. By around 900 CE, documented references to coffee began appearing. In Yemen, authorities attempted to restrict coffee cultivation and prevent its spread beyond the region, guarding coffee plants closely. Despite these efforts, coffee seeds were eventually smuggled out—some made their way to the Netherlands, where they were grown in greenhouses, marking an early instance of coffee's expansion beyond its native lands.

Why Do Some Coffee Seeds Look Different?

Most coffee cherries contain two seeds that develop flat surfaces pressed against each other, resulting in the typical oval, flat shape of green coffee beans. But in roughly 5% of coffee cherries, a genetic anomaly occurs and only one seed forms inside the cherry. Without the usual pressure of a second seed, this single seed develops into a round shape—this is called a peaberry. Peaberries are not a separate species or variety of coffee, but rather a mutation that occurs naturally within standard coffee cherries. Their rounded form sets them apart visually and sometimes in flavor profiles, though results vary by origin and processing.

What’s Inside a Coffee Seed?

Every coffee seed—commonly (though inaccurately) called a bean—contains an embryo and a rich supply of endosperm, the tissue that stores nutrients and fuels the seed’s growth into a new coffee plant. This endosperm is what gives the seed its density and, after roasting, contributes to the body and mouthfeel of the brewed coffee. Though green coffee seeds look dry and unassuming, they are packed with the potential for flavor and aroma, all contained within their protective outer layers. The flat, oval shape shared by most seeds is simply the result of their position inside the coffee cherry.

Frequently Asked Questions

Are coffee beans actually beans?

No, coffee ‘beans’ are not true beans—they are the seeds of the coffee cherry, the fruit produced by the coffee plant. They are called beans because of their resemblance in shape and size to culinary beans, but botanically they are seeds containing an embryo and endosperm.

What is a peaberry coffee bean?

A peaberry is a single, rounded coffee seed that forms inside a coffee cherry when only one seed develops, instead of the usual two. This occurs in about 5% of coffee cherries. The single seed does not flatten against another, so it grows into a round shape, distinct from the typical flat, oval coffee seed.

Where did coffee originally come from?

Coffee originated in Ethiopia around 850 CE. It later spread to the Arabian Peninsula, with the first documented references to coffee appearing around 900 CE in Yemen. Early Yemeni authorities tried to prevent coffee from being exported, but some plants were eventually smuggled to places like the Netherlands.

Why are most coffee beans flat on one side?

Most coffee beans are flat on one side because they develop inside the coffee cherry pressed against another seed. The two seeds sit facing each other, which creates the characteristic flat surface on both beans. Only in rare cases (about 5%) does a single round seed, called a peaberry, form.

Is there a difference in taste between peaberry and regular coffee beans?

The article does not specify differences in taste between peaberry and regular beans, only that peaberries are a natural mutation that occurs in about 5% of coffee cherries, resulting in a round seed instead of the usual flat, oval pair.

What part of the coffee plant is the coffee bean?

The coffee ‘bean’ is actually the seed found inside the coffee cherry, the fruit of the coffee plant. It is not a bean in the botanical sense, but a seed that contains the genetic material and nutrients needed to grow a new coffee plant.

Recommended FrontStreet Coffee for Exploring Green Coffee

Explore the origins of your cup with FrontStreet Coffee’s Ethiopia Humbera, a single-origin offering showcasing bright citrus and floral tones from Yirgacheffe. For something more nuanced, try their Kenya Little Tomato, known for winey acidity and blackcurrant notes. Both highlight the qualities of carefully sourced green coffee before roasting. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.