Coffee is not a legume, despite common confusion surrounding its botanical identity. Coffee belongs to a completely different plant family than true beans. This misconception arises because the harvested coffee seed visually resembles the dried seeds of true legumes. Understanding the precise botanical classification of both plant types clarifies why coffee is distinct from crops like peas or lentils.
Defining the Legume
A legume is defined by its membership in the Fabaceae family (Leguminosae). This plant family is one of the largest in the world, encompassing nearly 20,000 known species of flowering plants. The defining characteristic of the Fabaceae family is its unique fruit structure: a simple, dry fruit that develops from a single carpel, called a pod or legume.
This pod typically splits open along two seams at maturity to release the seeds inside. Common examples of true legumes include peas, lentils, peanuts, and various types of beans, such as kidney, black, and pinto beans. Many members of this family also engage in a symbiotic relationship with Rhizobia bacteria, allowing them to fix atmospheric nitrogen in root nodules.
The True Botanical Identity of Coffee
The coffee plant belongs to the genus Coffea, which is a member of the Rubiaceae family, commonly referred to as the Madder family. This botanical placement immediately separates coffee from the Fabaceae family and the classification of a legume. The Rubiaceae family is composed primarily of tropical trees and shrubs and also includes plants like gardenia and cinchona.
The item commonly called a coffee “bean” is actually the seed of the coffee plant’s fruit, which is botanically classified as a berry or drupe. This fruit is often referred to as a coffee cherry because of its small, round shape and red or purple color when ripe. Each coffee cherry typically contains two seeds nestled together with their flat sides facing inward.
The structure of the coffee fruit—a fleshy exterior surrounding one or two seeds—is completely different from the dry, splitting pod that defines a true legume. The seeds are separated from the surrounding pulp during processing before being dried and roasted. The seed is more accurately compared to the pit of a stone fruit like a peach or a true cherry, not a pod-borne seed.
Why Coffee is Called a “Bean”
The persistent use of the term “coffee bean” is rooted in common language and physical resemblance, not botanical fact. The roasted coffee seed is an oval, brown object with a crease down the middle, visually mimicking the appearance of many true beans, such as kidney beans. Early traders and consumers adopted the term “bean” because it was the most convenient and familiar way to describe the product in the marketplace.
This linguistic shortcut became deeply embedded in commerce and culture over centuries, establishing the common name used today. While botanists and growers accurately refer to them as seeds, the term “bean” has lost its strict scientific meaning in this context. Common usage has overridden precise scientific classification.