In biological terms, the tomato plant is a single species – Solanum lycopersicum. However, the variety of shapes and sizes in which it comes might lead you to believe otherwise. Decades of selective breeding and hybridization yielded a wide palette of tomato varieties, each with its own characteristic traits. The main motivation behind developing different tomato varieties is to make them more resilient and nutritious, but also to make them better-suited for specific uses – fresh consumption, cooking, canning, etc. Nevertheless, all tomato varieties can be roughly classified into two types – determinate and indeterminate tomatoes.
This division comes as a result of the different growing patterns the two types display. Determinate tomatoes are usually bushy and dwarfy in stature, while indeterminate varieties are taller. However, the differences don’t stop there. These two kinds of tomato varieties also display quite a few dissimilarities in other areas – the amount of foliage, maintenance needs, ripening time, and texture, size, and nutritive content of the fruit. In practical terms, these differences are essential for choosing a suitable tomato variety for your garden. Let’s look into the qualities and specifics of each type to learn how to make the right choice.
Determinate tomato varieties are most often cultivated for processing purposes (making juice, canning, freezing, etc.), but there are also certain varieties that are for fresh consumption. Although determinate tomatoes are most commonly seen in open fields, there are quite a few varieties preferred by indoor growers. The compact form of the plant and low pruning requirements are two considerable advantages of determinate tomatoes that make them suitable for cultivation in limited space – a common problem for indoor growers. Some of the most common varieties of determinate tomatoes include ‘Roma’, ‘Amelia’, ‘Rutgers,’ and ‘Dwarf Purple Heart’.
Basic qualities of determinate tomatoes:
- limited growth of stems and shoots, so they have a fixed size in maturity (usually up to 5 feet) and a dwarfy, bushy stature, which is why there is no need for staking or other support
- short planting-to-harvest period
- a limited number of flower buds
- fruits ripen at about the same time, in a time period that usually lasts around 10-14 days
- fruits have a high soluble solids content
- cultivated as annual plants
Due to their short stature, no need for growing support, and minimal pruning requirements, these tomatoes are a common choice of many growers seeking to save up on space, time, and maintenance efforts. Their swift development and even maturing makes harvest easy and allow mechanization. Suitable for growing in containers. Determinate tomatoes are commonly grown in temperate and cooler regions because their quick development is suitable for a shorter growing season.
Wild tomatoes, in their area of origin, are perennial plants that grow as vines and produce abundant foliage and small fruits in clusters. Heirloom, old varieties are quite similar to these wild tomatoes and have the same growth patterns, as well as the modern descendants of heirloom varieties. No matter the variety, we call plants with such qualities indeterminate tomatoes. Indeterminate tomatoes are most commonly cultivated for fresh consumption, and many of the well-known varieties, like ‘Beefsteak’, ‘Sungold’, ‘Brandywine’, and ‘Black Cherry’, fall into this group.
Basic qualities of indeterminate tomatoes:
- their stems can grow 6-12 feet and need staking, trellises, or other physical support to grow
- they require regular pruning to provide optimal conditions for flower and fruit development
- a great number of flower buds
- fruits develop slowly and ripen throughout the entire growing season
- grown as annuals but can be grown as perennials
Since indeterminate tomato varieties like warm temperatures and take more time to develop, cultivating them in open fields is common in tropical regions, where the long summer allows the plants to develop fruits steadily and abundantly. Indeterminate varieties are also popular in greenhouses and other indoor growing facilities, but they do require more space than determinate varieties due to their robust, trailing growth.
How to prune the two tomato types
Considering determinate and indeterminate tomato varieties have distinct growing patterns, they require different approaches in care and maintenance, which is especially prominent when it comes to pruning. The great philosophical question of tomato pruning is how many suckers to remove. Both determinate and indeterminate tomatoes produce suckers – small shoots that emerge from spots where stems and branches meet. Suckers can really make or break your tomato yields. They produce leaves, flowers, and carry fruits, significantly contributing to the overall yield, but if there are too many of them, they can negatively affect the size and the quality of the fruits. Knowing how many to remove is the greatest art of tomato cultivation, especially with indeterminate varieties.
Pruning determinate tomatoes
Having limited growth, determinate varieties require minimal pruning efforts to achieve their full potential. The only two things you need to look out for are the low-sitting leaves that are touching the ground, and all suckers below the first set of flower buds. Everything above the first flower set should be left intact until the end of the growing season. Over-pruning determinate tomatoes can seriously hamper the plant’s development and cut yields.
Pruning indeterminate tomatoes
In contrast, indeterminate tomatoes require regular pruning. Their suckers grow vigorously and can spend much of the plant’s energy on creating a big, thick canopy with numerous small fruits. Removing these suckers throughout the season is important for a number of things:
- ensures that the plant invests more energy into producing flowers and fruits
- improves aeration in the canopy, decreasing humidity and thus the likelihood of pathogens infecting the plant
- lessens the space required for plant cultivation
When and how to prune depends on the specific variety, desired shape of the plant, and the part of the growing season. There isn’t a single right way to prune indeterminate tomatoes, and different growers employ different approaches for different varieties. Regardless, all growers can agree on the five basic rules of indeterminate tomato pruning:
- All leaves that are touching the ground should be removed – As they sit too low on the plant, they are not photosynthetically efficient. But far more importantly, they increase the threat of a pathogen attack, as splashes of watering water can transfer harmful bacteria and fungi from the soil to the leaves, infecting the whole plant.
- Remove the flower buds if the plant is too small (less than 14-20 inches, depending on the variety) to improve the growth of roots, stems, and foliage – If the plant started to produce flowers before properly developing stems and foliage, that can support the growth, it is best to remove them, along with the suckers underneath them. Leaving suckers grow will lead to a wide, heavy canopy that requires a lot of space and support to carry fruits throughout the season. The fruits of such plants tend to be small.
- If you are pruning early in the season, always give your plants time to rest from the shock, at least for 1 month.
- Pinch off suckers on a weekly basis during summer – This will ensure that the plant is putting more of its nutrients and energy into fruits during the crucial time of fruit development. Also, it is best to remove suckers when they are small and easy to separate from the plant, as it causes minimal stress.
- Never remove more than a third of the plant’s aerial green mass – Although indeterminate tomatoes benefit from regular pruning, it is very important to not overdo it. Removing too much green mass inflicts great stress on the plants, leading them to focus their energy on recovering instead of flower and fruit development.
Tomatoes are amazing and fun plants to grow. If you have some space and are up for a challenge, get yourself an indeterminate variety, but if you’re tight with available time and looking for something suitable for containers, then a determinate variety is the best option. I hope this text provided more context on the essential differences between the two types. If not, feel free to leave us your questions in the comments.
- Heuvelink, E. (2018). Tomatoes (Crop Production Science in Horticulture, 27). CABI.