In order to keep tomato plants healthy and free from disease, I always prune my plants. Whether the plants are tall and slender or short and bushy, some selective pruning is always beneficial.
In this article, I’ll share my method for pruning tomato plants properly. I’ll cover indeterminate and determinate types (and the differences for trimming). I will also be specific about timing and technique for pruning your plants.
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What Is Pruning?
Before we get into the process for pruning, I want to cover the basics. What is pruning in the first place, and why is it important for tomato plants?
Pruning is the process of removing select foliage or branches from plants. This is done to encourage a desired growth pattern and avoid overcrowding in your garden.
However, removing random parts of your tomato plant is not good. There are 3 major parts of each tomato plant that you should be aware of. Here, I’ll explain each of them and how they relate to the pruning process.
Tip: Always use clean pruning shears or a sharp blade to prune your tomatoes. Using your fingers can introduce pathogens to your plants.
For indeterminate types, sucker shoots are your primary target for pruning. These secondary stems will attempt to grow from every node on your plants. If allowed to mature, they will rob or “suck” energy from the main stem, hence the name.
However, I don’t always remove suckers, and I’ll explain why when I cover determinate plant varieties. For now, you should learn to identify a sucker shoot when you see one.
The next important part of a tomato plant are the leaf branches. These occur along the main stem and extend outwards with nothing but leaves.
Of course leaves are important for all plants, as they are responsible for generating energy from sunlight. However, I always remove some of the leaves to reduce soil splashing onto the foliage, and to increase aeration throughout the plant.
I’ll get into exactly which tomato leaf branches to prune from your plants based on the type you are growing below.
Trusses (flower shoots)
Finally, the last portion of the plant to focus on are the flower trusses. These extend away from nodes and begin as a small, stiff branches of tiny flower buds. They will continue to grow, and eventually turn into your tomato fruits!
For the most part, we want to leave flower trusses alone. It can be beneficial to prune early flower buds if your plants are still small and indoors, but once they are growing outside, I leave them be to begin forming into tomatoes.
What Type of Tomato Plant Are You Growing?
Before you start trimming your tomato plants randomly, you should first determine which type you are growing. Tomato varieties fall into two large categories: Indeterminate and determinate.
Indeterminate tomatoes are most common, and grow in a continuous manner. Fruits ripen in stages, and plants continue to grow taller throughout the season. As older fruits are ripening, new fruits will be starting to form higher up on the plant. For this reason, indeterminate tomato plants are treated differently for both pruning and supporting. Skip to pruning indeterminate tomatoes.
Determinate tomatoes grow to a finite size, produce a single flush of fruits, and stop growing altogether. Some varieties may produce a second wave of fruits, but more often the plant simply dies after one large, simultaneous harvest. For this reason, pruning is treated differently for these varieties. Skip to pruning determinate tomatoes.
Generally speaking, determinate varieties only require bottom pruning and occasional leaf trimming, while indeterminate varieties require regular removal of sucker shoots and leaf branches.
To figure out which type you are growing, consult with the seed packet you purchased, the seed supplier’s website, or a search of the variety. Like I said, indeterminates are more common for garden varieties.
Note: If you are growing any ‘patio tomato’ varieties, these are most likely determinate plants. They remain small, and set fruit all at the same time.
I’ll get into more details on the technique I use to prune each variety in the sections below. If you’d like more info, learn more about determinate vs indeterminate tomatoes here.
Pruning Indeterminate Tomatoes
So, we’ve established that indeterminate tomatoes are more common for garden varieties. If your plants are indeterminate, this section will explain when and how to properly prune your tomatoes.
When to prune indeterminate tomatoes
After your tomatoes have been alive for about 6-8 weeks, the plant should begin producing sucker shoots. These secondary stems grow from nodes, just above leaf stems on. They start as a single leaf, but will eventually develop into a full-blown stem, with leaves and flowers.
As the season progresses, I prune any sucker shoots that develop. Indeterminate tomatoes are a bit more work than determinates in this regard, as you must continue to look out for new suckers and remove them promptly.
How to prune indeterminate tomatoes
For indeterminate tomatoes, we want to remove all of the sucker shoots, leaving a single, central main stem. This will keep the plant’s energy focused on continued upward growth, leaf branches, and trusses.
Note: Some tomato growers leave 1 sucker shoot on the plant to develop into a stem, and prune the rest. This will leave your plant with 2 main stems that can each be trellised and trained separately. If you have the vertical space this is a viable option as well.
If you leave a sucker shoot to grow, it will eventually form leaf branches and flowers of its own. This causes overcrowding, and uses more nutrients from the ground. This makes the plant more demanding for water, nutrients and space.
Before pruning, I let the suckers reach a large enough size to easily snip away with shears. If you use your hand, the plant injury may become infected.
By keeping the suckers pruned, the plant is less crowded, allowing for better airflow and making it easy to trellis the single main stem. For this, you can use string, but I like to simply use sturdy 8 foot garden stakes for training indeterminate tomatoes.
I also recommend bottom pruning indeterminate varieties. This involves removing leaf stems from the bottom of the plant on an ongoing basis as the plant grows taller. This helps the tomatoes ripen more quickly by sending hormones to the tomatoes, and improves aeration.
I will go into more detail on the process of bottom pruning below (skip there now).
Pruning Determinate Tomatoes
If you are growing determinate tomatoes, pruning is simpler. There is still some pruning to be done, but it mostly involves reducing crowding and improving aeration.
When to prune determinate tomatoes
Determinate tomato varieties often look similar or identical to indeterminates as a plant. However, since we know the plants will only produce a single, large crop, we want leave sucker shoots to develop.
However, as the plant begins to grow larger, I recommend bottom pruning to prevent the plant from becoming cramped. I usually begin pruning about 2-3 weeks after my tomatoes have been put into their final planting location.
How to prune determinate tomatoes
The best technique for pruning determinate tomatoes is to bottom prune, and trim some leaves during the year. This means that the leaf stems are the only part of the plant to remove.
Rather than pruning lots of leaves all at one time, I find it is best to lightly prune determinate plants every 1-2 weeks. I usually slice off 2-3 leaf stems every week and then allow the plant to recover and grow more before pruning again.
Tip: Always use a sharp blade or pruning shears to cut branches from your tomato plants. Breaking branches by hand can make for a messy injury that invites fungal spores and airborne pathogens.
Bottom Pruning and Trimming Tomato Leaves
Bottom pruning and occasional trimming is recommended for both types of tomatoes. These same principles apply to all varieties, and I recommend using these methods.
Bottom pruning is the process of removing foliage from the base of each plant to keep the soil from splashing on the leaves. It also helps improve airflow around the plant, reducing the chances of fungal infection.
For indeterminate varieties in particular, bottom pruning should be done throughout the season. The plants will produce the first set of fruits low on the plant. Once the fruits are beginning to ripen, remove 2-3 sets of leaves weekly, working from the bottom up.
The tomatoes will ripen more quickly when exposed to sunlight and the removal of nearby leaves changes the hormones of the plant. This directs more energy to ripening the fruits.
Trimming tomatoes involves removing leaves from various parts of the plant. This especially applies to determinate types, as they can quickly become overcrowded with multiple sucker stems actively producing leaves.
Trim regularly, about once per week, careful not to damage any developing fruits or trusses. Trimming some leaves will allow wind to blow through the plant instead of forming a high-humidity micro climate within your tomato, inviting blight.
I’ll say it again, always use a clean, sharp knife to get a quick, clean cut on each branch!
Tomato Pruning Tips
Here are a few tips to improve your success when pruning your tomatoes. I use these simple techniques help reduce the chances of disease, and decrease the time it takes for tomatoes to ripen on the plant.
- Remove leaves in the morning. Morning humidity is usually lower than in the afternoon. By trimming leaves or sucker shoots early in the AM, the wounds can heal and dry up before humidity goes up, decreasing the chances of infection.
- Cut leaf stems with a sharp blade. I highly recommend using a sharp blade to get a clean cut on every branch. Some growers use their fingers to break branches off, making for an imperfect wound that is much more susceptible to fungal infection.
- Remove leaves around ripening tomatoes. Trimming leaf branches weekly around ripening tomatoes will help them ripen more quickly. The fruits are exposed to sun, and the hormones from the leaves take away energy from ripening. This is accomplished during bottom pruning, but should be done regularly, especially with indeterminate varieties.
I hope this article helps you with pruning tomatoes in your garden. Without pruning, your plants may very well survive and produce fruit. However, I always prune to have a much healthier-looking and productive tomato garden.