The tomatillo (Physalis philadelphica), also known as the Mexican husk tomato, is a plant of the nightshade family bearing small, spherical and green or green-purple fruit of the same name. Tomatillos originated in Mexico and were cultivated in the pre-Columbian era. A staple of Mexican cuisine, they are eaten raw or cooked in a variety of dishes, particularly salsa verde.
The wild tomatillo and related plants are found everywhere in the Americas except in the far north, with the highest diversity in Mexico. In 2017, scientists reported on their discovery and analysis of a fossil tomatillo found in the Patagonian region of Argentina, dated to 52 million years B.P. The finding has pushed back the earliest appearance of the Solanaceae plant family of which the tomatillos are one genus. Tomatillos were domesticated in Mexico before the coming of Europeans, and played an important part in the culture of the Maya and the Aztecs, more important than the tomato. The specific name philadelphica dates from the 18th century.
Tomatillos are a key ingredient in fresh and cooked Mexican and Central-American green sauces. The green color and tart flavor are the main culinary contributions of the fruit. Purple and red-ripening cultivars often have a slight sweetness, unlike the green- and yellow-ripening cultivars, and are therefore generally used in jams and preserves. Like their close relatives, cape gooseberries, tomatillos have a high pectin content. Another characteristic is they tend to have a varying degree of a sappy sticky coating, mostly when used on the green side out of the husk.
Ripe tomatillos keep refrigerated for about two weeks. They keep even longer with the husks removed and the fruit refrigerated in sealed plastic bags. They may also be frozen whole or sliced.