The tomatillo (Physalis ixocarpa) is a member of the nightshade family just as tomatoes are. However, they should not be confused with green, unripe tomatoes even though tomatillos are sometimes called "green tomatoes", All tomatoes are in a different genus. The tomatillo is also known as a husk tomato, a jam berry, and sometimes called a husk cherry.
Tomatillos originated in Mexico and are a key ingredient in fresh and cooked Latin American green sauces. The tomatillo fruit is surrounded by an inedible, paper-like husk. As the fruit matures, it fills the husk and can split it open by harvest. The husk turns brown, and the fruit can be several colors when ripe – including yellow, red, green, or even purple – depending on the variety planted. Fruits should be picked while still firm in order to have the tart flavor expected for recipes in which they will be used. The purple and red-ripening cultivars often have a slight sweetness, making them more suitable for fruit-like uses such as jams and preserves.
Since Tomatillo plants are highly self-incompatible, two or more plants must be planted close to one another to ensure proper pollination. Isolated tomatillo plants rarely set fruit. Ripe tomatillos will keep refrigerated for about two weeks. They will keep even longer if the husks are removed and the fruits are placed in sealed plastic bags and stored in the refrigerator. They may also be frozen whole or sliced.