Heirloom tomatoes are not a single type of fruit but a category of open-pollinated, non-hybridized varieties whose seeds have been passed down for generations. Unlike the uniform produce bred for commercial transport and shelf life, heirlooms are grown primarily for their flavor and remarkable diversity. The concept of a standard size does not apply to this group, as their dimensions can range from less than an ounce to over two pounds, depending entirely on the specific cultivar.
Categorizing Heirloom Tomato Sizes
The smallest classification includes cherry and grape types, which typically measure one inch or less in diameter. These petite fruits generally weigh under two ounces, making them ideal for quick snacking or use in salads.
The next size class is the medium, or standard, slicing tomato, often ranging from two to three inches across. These fruits commonly weigh between four and twelve ounces, striking a balance between size and manageability. Varieties like ‘Cherokee Purple’ or ‘Green Zebra’ often fall into this medium range, making them versatile for many kitchen applications.
The largest category is the beefsteak, which includes many of the most famous heirloom varieties, such as ‘Brandywine’. These impressive tomatoes are typically three to six inches in diameter and frequently weigh one pound or more. Some exceptional beefsteak cultivars can even exceed two pounds, representing the maximum potential size for the fruit.
Genetic and Environmental Factors Influencing Size
The single greatest determinant of a tomato’s potential size is its genetic programming, as the cultivar dictates the maximum fruit weight it can achieve. For instance, a cultivar like ‘Brandywine’ is genetically predisposed to be a large fruit, while a ‘Black Cherry’ is not. Specific genes, such as the fw2.2 locus, play a significant role by negatively controlling cell division during the early stages of fruit development. Mutations in this gene that reduce its function have been linked to the evolution of larger-fruited varieties during domestication.
Environmental conditions, however, determine whether a tomato reaches its genetic potential. Consistent water availability is necessary, as irregular watering can stunt fruit growth and cause cracking. Nutrient balance is also a significant factor, with the availability of elements like potassium, phosphorus, and calcium supporting the cell expansion and overall fruit development.
How Size and Shape Determine Culinary Use
Large beefsteak and globe-shaped tomatoes are prized for their high flesh-to-seed ratio and robust, meaty texture, making them the standard choice for slicing. A single slice from these varieties, such as ‘Mortgage Lifter,’ can cover an entire slice of bread, perfect for sandwiches and burgers.
Medium-sized and plum-shaped heirlooms, like ‘Amish Paste,’ contain less water and more solid matter, which makes them excellent for cooking. Their density allows them to break down into rich, flavorful sauces or be preserved through canning without becoming overly watery. Smaller varieties, including cherry and pear shapes, are best utilized whole due to their intense sweetness and thin skins. These small fruits are frequently used for snacking, roasting, or tossing directly into salads.
Beyond size, unique shapes also impact use. For example, the heart-shaped Oxheart varieties are exceptionally dense with few seeds, making them ideal for eating fresh. Ribbed or pleated heirlooms, such as ‘Costoluto Genovese,’ hold their shape well when hollowed out, making them excellent for stuffing or baking.