04/16/2026
For all you tomato geeks out there (takes one to know one👍).
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In the world of pomology (the study of fruit), the tomato is a multi-chambered BERRY. These chambers are called locules, and they are the architectural blueprints that determine a tomato’s shape, weight, and culinary use.
The number of locules in a tomato is a genetic trait that defines the "class" of the tomato.
A locule is the open space within the o***y of the flower where the seeds develop. It consists of the outer fleshy wall called the “pericarp”. Then the central core where seeds are attached is the “placenta”. The “locular gel” is the jelly-like substance surrounding the seeds, which holds the majority of the fruit's flavor-defining acids.
The evolution of the tomato from its wild ancestors to the modern beefsteak is essentially a history of locular expansion!
Cherry and Grape Tomatoes (2 Locules)
Wild tomatoes and their closest domesticated relatives, like the cherry tomato, are typically bilocular. They have two clean, symmetrical chambers separated by a single central wall (septum). Because they have fewer walls and a high ratio of gel to flesh, they tend to be "poppy" and burst with juice when bitten. This simple structure makes them very stable and resistant to cracking.
Plum and Roma Tomatoes (2 to 3 Locules)
Often called "paste" tomatoes, these are bred for processing rather than fresh snacking. They usually possess 2 or 3 locules. The goal for a Roma is low moisture. Evolution and breeding have favored thicker pericarp walls and smaller locular cavities with less gel. This results in a "meaty" fruit that stands up well to canning and sauce-making without requiring hours of reduction to boil off excess water.
Standard Round/Slicer Tomatoes (3 to 5 Locules)
These are your classic "supermarket" or "garden" tomatoes. They typically feature 3 to 5 locules arranged in a radial pattern. This increase in locule number creates a firmer, more rounded fruit. The extra internal walls provide structural integrity, allowing the tomato to be sliced without collapsing.
Beefsteak Tomatoes (Multi-locular / 6+ Locules)
The GIANTS of the tomato world are defined by a genetic mutation called fasciation. Beefsteaks are "multi-locular," often containing 10, 20, or even more small, irregular locules scattered throughout the fruit. Instead of a clear central core, the placenta is often branched and "mealy" (in a good way). This complex internal webbing is what gives the beefsteak its massive size and "oblate" (flattened and often ribbed) shape. Because there are so many walls, a single slice of a beefsteak can cover an entire sandwich without falling apart.
The more locules a tomato has, the more "surface area" there is for seed attachment and gel production. However, it also creates more structural complexity, which is why beefsteaks are more prone to catfacing (scarring at the blossom end) and uneven ripening compared to the simple, two-chambered cherry tomato.
