To fully understand pruning tomatoes, you need to know the three types of tomatoes. When pruning your tomatoes, first identify which kind of growth habit the plant has: determinate, indeterminate, or semi-determinate.
Pruning Determinate Tomatoes
These tomatoes are sometimes called “bush” tomatoes. They tend to be bushy, more compact, and yield tomatoes all at once. Common tomato varieties considered determinate include most canning tomatoes, like Roma, and similar paste tomatoes. The main reason why people make sauces out of determinate tomatoes is that they tend to give all their fruit at once, making it perfect for sauce recipes. Determinate tomatoes make great tomatoes for those with little space, like patio growers. Pruning tomatoes like determinate Roma varieties is less work than pruning indeterminate varieties because the plant will grow to produce a set of fruit and will not continue to produce over a long period of time. Additionally, since determinate tomatoes are “bushier,” the plants will not require constant pruning like indeterminate tomatoes.
Pruning Indeterminate Tomatoes
These tomatoes are sometimes called “pole” tomatoes. That is because they grow long vine-like stems and tend to need a structure to keep them up off the ground. These tomatoes will yield over a long period instead of all at once. Popular varieties are Yellow Pear and Green Zebra. We have seen these varieties get nine feet or taller with support on our farm. The benefit of growing this kind of tomato is that you have tomatoes all season long in small batches that are easy to handle. A potential negative is that they require a generous amount of staking if you want to keep them tidy.
For a patio grower, we recommend determinate tomatoes because they are better suited for pots. When pruning tomatoes of indeterminate varieties, you will want to remove the suckers to direct the energy into the fruits and discourage the plant from producing excessive new growth in lieu of ripening current tomatoes on the plant. This way of pruning tomatoes is best for varieties you grow using our low and lean Tomahook method. It allows you to maximize yield and minimize the space needed for the plant as you are constantly directing the energy flow into the tomatoes.
These tomatoes are a mix of determinate and indeterminate. They tend to be much more compact than an indeterminate variety of tomato but will yield over a long period. When pruning tomatoes that are semi-determinate varieties, you will want to remove suckers and prune for the shape and size needed to keep the plant neat and tidy. Still, you will be pruning much less than pole varieties like Green Zebra or Lucid Gem.
Keep in mind that this information is strange for Southern California growers because our mild climate allows for tomato production year-round in many places. When we speak about setting fruit all at once, it is the difference of a plant ripening one tomato at a time or, in the case of something like a San Marzano tomato, ripening handfuls of fruit all at once. Both an indeterminate or determinate tomato variety, in a mild climate, can yield for long periods.
Now that you know the various kinds of tomatoes, you can make better decisions about pruning tomatoes.
Final Considerations on Pruning Tomatoes
When growing indeterminate tomatoes, pruning is essential for maximized fruit production. An indeterminate tomato plant will grow copious amounts of foliage and very little fruit if not pruned in a way that tells them where to put their energy. For indeterminate tomatoes, it is important to cut off the suckers. The suckers are the stems that grow between the main stock and a branch. They grow right in the crotch of these two parts and will suck energy from the tomatoes setting above it if not trimmed away.
In the photo below, we show two types of pruning of suckers. One is simple pruning which is recommended in mild areas or coastal areas with more moisture. This pruning allows for better airflow and fewer disease pressures. In areas that get very hot, tomatoes can suffer from sun scald, and because of this, we recommend the Missouri pruning method, which allows for some foliage to be left to shade tomatoes.
Why do you prune off suckers?
On indeterminate plants, the suckers grow new sets of shoots, flowers, and eventually tomatoes. However, the new growth will take vital energy away from the already formed flowers and future tomatoes. By curbing the plant’s innate desire to grow more foliage, you can ensure its energy goes into developing tomatoes.
On determinate tomatoes, this practice is not as essential but still advised. Why? Determinate tomatoes have a set number of tomatoes they will produce, and pruning has little influence on that. However, you still want to prune to minimize the pest issues common with tomatoes, like whiteflies. Increased airflow is vital for any healthy tomato plant.
As discussed above, tomato pruning for semi-determinate tomatoes is a combination of removing excessive suckers and pruning for shape and size. It is not essential as it is with indeterminate tomato plants.