The tomatillo (Physalis philadelphica or Physalis ixocarpa), often called a husk tomato, is a small, spherical fruit encased in a papery husk and is a staple ingredient in Mexican cuisine, most notably in salsa verde. These plants are botanically classified as tender perennials, meaning they possess the genetic ability to live for multiple years. However, due to their extreme sensitivity to cold, tomatillos are almost universally cultivated as warm-season annuals outside of consistently tropical or subtropical climates. This dual nature explains the common confusion about whether the tomatillo is an annual or a perennial.
Understanding Tomatillo’s Life Cycle
The classification of a plant depends on the length of its life cycle. An annual plant completes its entire life cycle—germination, growth, seed production, and death—within a single growing season. In contrast, a perennial plant lives for more than two years, often growing and producing fruit season after season. The tomatillo belongs to the Solanaceae family, the nightshades, which also includes tomatoes and peppers.
Tomatillos are specifically categorized as “tender perennials” because their long-term survival is contingent upon a consistently warm environment. In their native regions of Mexico and Central America, where frost is absent, a tomatillo plant can persist for several years, demonstrating true perennial behavior. For gardeners in most of the world, however, the plant’s tender nature means it will be killed by the cold, forcing it into an annual cycle.
The Impact of Climate on Survival
The primary factor determining the tomatillo’s lifespan is the presence of frost. Tomatillo plants are highly sensitive to freezing temperatures and will not tolerate even a light frost. Optimal growth occurs in a warm climate, with preferred temperatures ranging between 68 and 100 degrees Fahrenheit (20 to 38 degrees Celsius). If temperatures drop below 61 degrees Fahrenheit (16 degrees Celsius), plant growth becomes poor, and freezing temperatures will kill the plant outright.
Only regions with USDA hardiness zones of 9 or higher, or similar climates that are completely frost-free, allow tomatillos to maintain their perennial status. In these warm environments, the plant can continue to grow, flower, and produce fruit year-round. For the vast majority of gardeners in temperate zones, the predictable arrival of a hard freeze necessitates treating the plant as a temporary, single-season crop.
Cultivating Tomatillos as Annuals (The Standard Practice)
Starting and Transplanting
Because of the temperature limitations, most gardeners start tomatillos indoors to maximize the warm growing season. Seeds should be sown six to eight weeks before the last expected frost date in your area. This head start ensures the plants are ready to be transplanted outdoors once all danger of frost has passed, and the soil temperature has warmed to at least 60 degrees Fahrenheit (15.5 degrees Celsius).
Pollination Requirements
A crucial cultivation detail is the requirement for cross-pollination to produce fruit. Tomatillos are self-incompatible, meaning a single plant cannot pollinate itself or another plant of the same exact genetic makeup. Therefore, gardeners must plant at least two separate tomatillo plants, and ideally two different varieties, to ensure successful fruit set.
Harvest and End of Season
After transplanting, the vigorous plants grow quickly and are generally ready for harvest within 65 to 100 days. The fruit is ready to pick when it fills the papery husk, which turns from green to a tan color and often begins to split open. Once the first frost of autumn arrives, the plant’s life cycle is over, and it should be removed from the garden and composted.