The San Marzano tomato, beloved for its low acidity and firm, meaty texture, is the gold standard for Italian sauces and canning. Successful cultivation begins with understanding its natural growth pattern. Knowing if a tomato plant is determinate or indeterminate is the foundational step for proper garden planning, impacting required space and harvest timing. This classification dictates the plant’s overall structure and how it produces fruit throughout the growing season.
Defining Determinate and Indeterminate Growth
Tomato plants are categorized into two main growth habits based on how their stems terminate and set fruit. Determinate varieties, often called “bush” types, grow to a predetermined, compact height, typically reaching two to four feet tall. Vegetative growth stops once the terminal bud on each stem produces a flower cluster. This results in the majority of the fruit ripening within a short, concentrated window, ideal for processing large batches at once.
Conversely, indeterminate varieties exhibit a vining habit that continues to expand until killed by frost or disease. These plants are true vines, constantly sending out new stems, leaves, and flower clusters throughout the season. Indeterminate plants do not stop growing at a set height and can easily reach six to eight feet or more. This continuous growth requires significant vertical support but ensures a steady, prolonged harvest from mid-summer until the end of the season.
The San Marzano Verdict: Indeterminate Growth Habit
The traditional, heirloom San Marzano tomato, such as the ‘San Marzano Redorta’ strain, is an indeterminate variety. This means the authentic plants grow as vigorous vines that require substantial planning and maintenance to manage their height and sprawling nature. They produce fruit clusters progressively along the stem for weeks, offering a continuous yield rather than a single burst. These plants will keep growing and setting fruit as long as warm weather persists.
Due to the tomato’s popularity, some seed companies offer “San Marzano-type” varieties or hybrids labeled as determinate or semi-determinate. These newer compact versions are often bred for container gardeners or those who desire a concentrated harvest. Always check the seed packet or plant tag for the specific growth habit, as a determinate type will behave very differently than the traditional indeterminate heirloom.
Gardening Implications of Indeterminate Tomatoes
The indeterminate nature of traditional San Marzano tomatoes requires specific cultivation practices. Since the plants are vigorous vines that can exceed six feet in height, they require strong vertical support from the moment they are transplanted. Simple, light-duty tomato cages are usually insufficient. A sturdy trellis, strong staking system, or the Florida weave method is necessary to bear the weight of the continuous growth and heavy fruit load. Without proper support, the vines will sprawl onto the ground, increasing the risk of soil-borne diseases and pests.
Regular pruning is also highly recommended for this growth type. This involves removing suckers—the small shoots that emerge between the main stem and a leaf branch. Pruning directs the plant’s energy toward fruit production instead of excessive foliage. This maintenance strategy improves air circulation and reduces the likelihood of fungal issues, providing the gardener with a steady supply of flavorful tomatoes for sauces and canning.