Whether or not to prune tomatoes is perhaps the most famous debate amongst gardeners. There are a number of conflicting opinions about the benefits and drawbacks of pruning tomato plants, mostly regarding the removal of suckers.
Although letting suckers grow out can create new branches and thus more fruit, they should be kept under control to prevent tomato vines becoming a jungle-y and disease-prone mess.
So how do we reach this pruning balance and ensure our tomatoes are both high yielding and healthy? Let’s break it down section by section to really understand the ins and outs of trimming tomatoes.
Why pruning can be beneficial for tomatoes?
Pruning tomatoes is a subject of debate because it is thought that leaving branches and suckers to produce new fruit will increase yield. Although this is true and pruned plants may produce slightly fewer fruits, the fruits are more likely to succeed, reach a large size, and be healthy.
But make sure you check which variety of tomato you have, as even though determinate tomatoes can benefit from end of season pruning to ripen fruits, it is only the indeterminate varieties that need to be regularly pruned to control growth.
A reminder: Determinate tomatoes (bush tomatoes) have a predetermined size they will grow to and will just provide one or two main harvests, and indeterminate (vine tomatoes) varieties will continuously grow and produce fruit until they are stopped by frost or another intervention.
Here are the main reasons why pruning vine tomatoes can be beneficial:
When to prune your tomato plants?
Determinate tomato varieties should only be pruned right at the end of the season, when they are being topped to ripen the fruits.
Since determinate tomatoes have a predetermined growth pattern and will max out at a certain size, pruning is not necessary throughout the season.
However indeterminate tomatoes are known to become monstrously tall and out of hand if action is not taken to prune back ambitious new growth, and should be pruned throughout the season.
Since the methods and techniques differ as the plant matures, the main pruning stages throughout the life cycle of a tomato plant can be divided into three groups:
Early Season Pruning (Only Indeterminate)
The first point at which tomatoes can benefit from pruning is early in the season, right at the transplanting stage and for several weeks afterwards.
Depending on how tall your transplants are, this stage of pruning should take place when the tomatoes are 10-18 inches tall. This is when the plant is focused on establishing itself, so pruning is designed to facilitate that process.
Mid Season Maintenance (Only Indeterminate)
Pruning tomatoes in the middle of the season is focused on plant maintenance and disease prevention, and should be done continuously.
There are no strict guidelines on how tall the plants are at this stage, as they will be constantly growing and producing fruit!
Late Season Topping (Both Determinate and Indeterminate)
The last time your tomatoes will get a pruning is at the very end of the season, and this is the only time determinate tomatoes should be pruned.
This is when the plants have reached their maximum height (for determinate varieties), or you want to stop their growth (indeterminate varieties) and get all the remaining fruits to quickly ripen up before the weather turns, at least 3 weeks before the first frost. Depending on your growing zone, this is usually done in the late summer or early fall.
How to prune tomatoes
Whether you are pruning leaves, branches, flowers or suckers, you should always use sharp and clean pruning shears or scissors.
Make sure your hands are also clean and that the plants are completely dry to prevent spreading disease between them.
Here are the methods for pruning your indeterminate tomatoes at different points in the season:
1: Early-Season Tomato Plant Pruning
Right after your tomatoes have been planted, pruning is focused on helping the plant direct its energy towards establishing itself in the soil and developing a strong root system.
Here’s how to do that:
2: Mid-Season Pruning Of Tomato Plants
Now your tomatoes have gotten out of their initial growing stages, they are probably beginning to set fruit and get some significant height.
Mid season pruning is all about maintenance and keeping a watchful eye out for diseases or pests that could compromise the health of your plants.
You also will notice continuously ripening fruit, and do some modified late season pruning at this stage. These are the basic steps of pruning tomatoes in the middle of the season:
3: Pruning Tomato Plant Later In The Season
At the end of your tomato growing season, you will want to prune both your determinate and indeterminate plants to help the existing fruits ripen up!
The first frost might be coming soon, and you don’t want your plant wasting energy on growing new flowers or leaves, you just want 100% of the energy to be on the fruits.
Follow these steps at the end of the season:
Tomato Pruning Tips To Remember
Maya is a freelance content writer and avid gardener currently based in Sweden. She gained her BA in Environment and Geography in Canada, which is also where she first learnt about the detriments of the industrialized agricultural system. During the summer she began farming through the WWOOF program, and over the next six years has continued to grow and learn at a number of organic farms and gardens across the US and Canada. She is passionate about the role of regenerative agriculture in wildlife conservation and climate change mitigation, and thinks growing your own food is a key part of revolutionizing the system. In her free time she likes to read, garden, and pet nice dogs.