The growth habit of a tomato plant dictates nearly every aspect of its cultivation, from the space it requires to the timing of its harvest. Recognizing this fundamental difference is paramount for planning a successful season and managing expectations for fruit production. Whether a variety grows as a compact bush or a sprawling vine directly impacts the necessary support system, pruning strategy, and fertilization schedule. This classification determines if you will harvest a concentrated batch for canning or a steady supply for fresh eating.
Understanding Determinate and Indeterminate Growth
Tomato varieties are classified into two primary growth types, each exhibiting a distinct physiological pattern of stem growth and fruit setting. Determinate varieties, often called “bush” types, grow to a fixed height, typically reaching between three and five feet tall. Their growth terminates when the main stem develops a flower cluster at its tip. This results in the plant setting and ripening the majority of its fruit in a short, concentrated window, often within one to two months, making them ideal for large-batch processing like canning or sauce-making.
In contrast, indeterminate varieties are the “vining” types, which possess an open-ended growth pattern. These plants continuously produce new stems, leaves, and flower clusters along their entire length until frost halts their progress. Indeterminate plants can easily reach heights of six to fifteen feet, requiring significant support, and they provide a steady supply of fruit throughout the entire growing season. A third, less common classification, semi-determinate, offers a more compact vine with a longer production period than the bush types.
The Growth Habit of Plum Tomatoes
The term “plum tomato” refers to the fruit’s elongated, cylindrical shape and its dense, meaty texture, not its botanical growth habit. Therefore, plum tomatoes can be either determinate or indeterminate, depending on the specific variety selected. The most widely grown commercial plum tomato, the classic ‘Roma,’ is genetically a determinate variety. This determinate nature is highly valued in commercial agriculture because the concentrated, simultaneous ripening facilitates an efficient, single-pass mechanical harvest for processing.
However, many heirloom plum tomatoes, such as the famous ‘San Marzano,’ are distinctly indeterminate. The authentic ‘San Marzano’ is a vigorous vining type that requires extensive support and produces its flavorful fruit continuously until frost. Gardeners must always check the seed packet or plant tag for the specific variety, as hybrids of Romas and San Marzanos exist, sometimes exhibiting a semi-determinate or a different growth habit.
Cultivation Techniques Based on Growth Type
The determinate and indeterminate classifications demand fundamentally different approaches to garden management. Determinate plum varieties, like Roma, require minimal support, usually a short, sturdy cage around three to four feet high to bear the weight of their concentrated fruit set. Conversely, indeterminate varieties, such as San Marzano, need tall, heavy-duty structures like six to seven-foot stakes or extensive trellising to support their continuous, sprawling growth.
Pruning techniques also differ significantly between the two types. Determinate plants should not have their suckers—the small shoots that emerge between the main stem and a leaf branch—removed. These shoots produce much of the plant’s limited fruit yield, and removing them substantially reduces the overall harvest. However, removing lower leaves near the soil improves air circulation and disease prevention.
Indeterminate varieties benefit greatly from the regular removal of suckers to manage the plant’s size and focus its energy. Pruning these vining types directs the plant’s resources toward the development of larger, higher-quality fruit. This practice maintains a healthy, manageable plant that continues to produce steadily throughout the season.
The feeding schedule should also align with the growth habit. Determinate plants require a high initial nutrient load, particularly phosphorus and potassium, to support the rapid development of their one large, simultaneous crop. Indeterminate plants, which are continuously growing and fruiting, need a sustained, consistent application of balanced fertilizer throughout the season to maintain steady production.