The belief that all heirloom tomatoes are indeterminate is a common misunderstanding among gardeners. This idea arises because many famous and flavorful heirloom varieties, like ‘Brandywine’ or ‘Cherokee Purple,’ exhibit this vigorous growth pattern. However, the term “heirloom” refers to a tomato’s lineage and genetic stability, while “indeterminate” describes its physical growth habit. Understanding these two distinct classifications is important for planning planting space and harvest schedules.
Defining Determinate and Indeterminate Growth
Tomato plants are classified into two growth habits: determinate and indeterminate, which dictate their size, shape, and fruiting pattern. Determinate varieties, often called “bush” tomatoes, grow to a fixed height, typically reaching three to four feet tall. Once the terminal bud produces a flower cluster, the plant’s vertical growth ceases, leading to a compact, self-supporting structure that requires less staking or caging. This habit causes the plant to ripen the majority of its fruit within a short, concentrated period of about two to three weeks. This makes them ideal for gardeners who want a large yield all at once for canning or processing.
Indeterminate tomato plants are true vines that continue to grow, flower, and produce fruit continuously until frost or disease kills the plant. These varieties can reach heights of six to ten feet or more and require significant support, such as tall stakes or heavy-duty cages, to manage their sprawling growth. Since they produce fruit gradually over a long period, indeterminate plants provide a steady, season-long supply of fresh tomatoes, perfect for daily harvesting and fresh eating. These varieties often require regular pruning to maintain an open canopy and direct the plant’s energy toward fruit development.
What Makes a Tomato an Heirloom?
The classification of a tomato as an heirloom relates to its genetic history and production method, not its physical growth habit. Heirloom varieties are open-pollinated, meaning seeds saved from the fruit will grow “true to type” and produce plants identical to the parent, provided cross-pollination is prevented. This distinguishes them from modern F1 hybrid varieties, which do not reproduce true to type from saved seed. A variety is generally considered an heirloom if it has been grown and passed down through generations for a significant period, often benchmarked as 50 years or introduced commercially before 1940. This stability ensures the genetic line is consistent, retaining unique flavors and characteristics.
The Range of Growth Habits in Heirloom Varieties
Since “heirloom” is a historical classification and not a growth classification, these tomatoes can be found across the entire spectrum of growth habits. The most recognized and widely grown heirlooms, especially the large-fruited beefsteak types, are predominantly indeterminate, including famous examples like ‘Brandywine’ and ‘Black Krim’. These vining heirlooms are prized for their complex flavors and ability to produce fresh fruit from mid-summer until the first frost. They demand the most attention in the garden due to their massive size and need for robust trellising.
Determinate heirloom varieties offer a manageable option for home growers. These heirlooms, such as certain ‘Roma’ types or the Russian ‘Black Sea Man,’ grow into compact bushes well-suited for container gardening or smaller spaces. Varieties like ‘Marglobe’ and ‘Rutgers’ are classic determinate heirlooms that produce a concentrated crop. This is beneficial for making large batches of sauce or canning. Knowing the specific growth habit of an heirloom before planting is necessary to provide the correct support and plan for harvest timing.