Heirloom tomatoes, by definition, are not new. They are varieties of the fruit that fell out of mainstream cultivation for various reasons, such as shorter shelf life or delicate skins that make them difficult to transport. But they are often very flavorful, distinctive tasting, have striking appearances or have a combination of those qualities that make them prized by many chefs and consumers.

Over the past couple of decades farmers and horticulturalists have brought the seeds of these distinctive tomato varieties out of storage and have been growing them, providing fruits with distinctive terroir, local appeal and hyper-seasonality.

Heirloom tomatoes come in a wide variety of sizes, shapes, and colors and add a distinctly premium quality when sliced and incorporated into sandwiches, salads and other dishes.

Market research firm Datassential reports that mentions of heirloom tomatoes are up by 60% over the past four years. But there’s still plenty of room for expansion: They are still only found on 5% of menus across the country.

Click through the gallery to learn more about this Flavor of the Week and see how one restaurant is using heirloom tomatoes on its menu.