From The Food Encyclopedia by Jacques Rolland and Carol Sherman
Also husk tomato, jamberry. A Mexican perennial, Physalis ixocarpa, originally cultivated by the Aztecs, the tomatillo looks like a green tomato wrapped in a parchment husk; it's related to the cape gooseberry, which is also encased in a husk. It belongs to the nightshade, or Solanaceae, family, along with the tomato, eggplant, pepper, huckleberry and potato. It's technically a berry, firmer than the tomato, about 1 inch (2.5 cm) in diameter, usually harvested when still green and tart; it turns purple or yellowish when fully ripe. The tomatillo is the most trouble-free summer crop to grow in the Northern Hemisphere; it has never suffered any of the diseases that have affected the other solanaceous vegetables, nor do insect pests bother it. It grows in every U.S. state, except Alaska. The husk must be kept on until it's ready to be eaten.
