If this is your first year attempting to grow tomatoes, I get it – pruning can be a confusing topic. When I grew my first outdoors indeterminate tomatoes I did minimal pruning, and was quickly overwhelmed by the amount of growth I had to deal with. To make matters worse, my tomato plants suffered from blight because they were so bushy and close together.
In the following year, I decided to prune my indeterminate tomato plants dilligently – and let me tell you, it made all the difference! I had a generous supply of ripe tomatoes all the way to the first frost. So how did I do it, here in zone 6, and how often did I prune my fast-growing tomato plants?
How frequently you prune tomato plants depends on the season and their rate of growth. Once a week should be fine at first, but during the height of summer, two times a week is better. All you need to do is check each tomato plant for suckers and pinch them off as soon as you notice them.
But suckers, while the most important part of pruning, aren’t the only thing to keep in mind. Read on if you want to learn how to make pruning a habit, what to cut and what to avoid.
When should you start pruning your tomato plant?
Pruning actually starts the moment you transplant your tomato plant in the ground. Whether you started your own tomato seedlings or not, you need to prune them considerably before planting them.
Start with pinching the plant’s lower leaves. It’s best to bury your tomato seedlings deep, so there’s really no use for the lower leaves, since they cant photosynthetize in the soil. Don’t worry about the long stem inside the ground – it will set roots and make your plant stronger.
Once you have your tomato seedling in the ground, remove the remaining leaves that might be touching the soil. You don’t want to attract any soil-borne disease into your fragile plants.
Lastly, pinch off any flowers that you might have, since you want your tomato plant to focus its energy into establishing a solid root system and creating new growth.
When the plant is at least 12 inches / 30 cm tall, you can start regularly checking for suckers, which we’ll cover in detail below.
Why prune tomato plants weekly?
The best way to grow indeterminate tomato plants outdoors is on a fence type trellis or using stakes. I chose to use individual stakes for each of my tomato plants. If you don’t prune your tomatoes at all, you’ll end up with a mess, not to mention poor airflow – the perfect recipe for attracting blight and disease.
Pruning weekly is best because those pesky tomato suckers don’t get to an unmanageable size and you can easily pinch them with your fingers instead of scissors or shears.
Tomato suckers grow fast, which I’m sure you’ll learn if you take a two-week vacation in the middle of a hot summer. Good luck deciding which stem to keep and which to discard when you have fruiting branches everywhere!
Another important reason to prune tomato plants weekly is because you’re doing two things at the same time: removing ineffective growth and training your tomato plant to grow up by tying it to your trellis / stake every single week. Soon enough, you’ll end up with tomatoes taller than you!
So what are we pruning exactly?
When pruning, we have to focus on four things:
- Leaves touching the ground
- Leaves beneath the ripening fruit
- Diseased leaves
Leaves touching the ground
This one is pretty self explanatory. You do it when planting your tomato seedlings, and you keep doing it if you notice any soil-level growth, or any leaves that you’ve overlooked. After doing this regularly for a few weeks, you’ll soon have a clean tomato stem at the base of the plant, clear of any growth.
The reason for clearing leaves close to the ground is because we don’t want rain (or water from your hose) splashing from the soil towards the lower leaves and contaminating them. As a general rule, when watering, keep your tomato foliage as dry as possible and only bottom water.
You’ll find tons of resources on suckers, how to identify them, how to prune them, etc. Put simply, suckers are secondary stems that grow at a 45 degree angle from the main stem and the tomato leaf below. They will most likely set flowers and fruit, but their fruits will be smaller and less productive. It’s best that you regularly remove them.
Leaves beneath a fruit that’s ripening
Indeterminate tomatoes grow fruit clusters that ripen starting with the cluster that’s lowest to the ground. In order to prevent the plant’s energy from going to the leaves instead of the fruit, once the fruits are starting to yellow and look glassy, you can remove ALL the leaves below the fruit cluster, so that the plant can focus on ripening those delicious tomatoes.
That being said, you might notice yellowing or wilted leaves sometimes, and it’s okay to snip them off and leave the tomato plant in the ground.
Should you prune suckers that have flowers on them?
The short answer is yes. You’ll see suckers developing flowers and fruit quite fast, but don’t be fooled. They won’t be as productive as the main stem. If you’re growing your indeterminante tomatoes in a single-stemmed manner (and I strongly suggest that you do), you should strive to prune any and ALL suckers.
But even if you do your best, you’ll often notice those sneaky growers to escape you every once in a while. If they already have tomatoes ripening on them, just cut their tops off to prevent further growth and move on.
Many gardeners decide to allow their indeterminate tomatoes to develop two stems – the main one and a sucker that’s low to the ground. If that’s you, that’s perfectly fine, although I should say that this method works best for fence trellises and not so much for individual stakes.
Can you overprune a tomato plant?
If you know WHAT to prune – a.k.a strictly suckers – it’s impossible to overprune an indeterminate tomato plant. The plant will have enough foliage to sustain itself, but not too much to block light or cause airflow problems.
However, if you remove too many essential leaves off the tomato plant, this can lead to sun scald on your tomato fruit. If you notice the plant suffering, like leaves curling or droopy-looking plants, don’t remove those leaves. Tomato leaf curl is rarely a sign of disease, rather, a sign of plant stress, so keep those leaves intact.
Another major pruning mistake is pruning your determinate tomatoes. You really don’t need to do that – these plants have a set amount of leaves and fruit that’s optimal for their growth, and pruning will only hinder their productivity.
Use common sense and keep practicing – you’ll soon learn the perfect balance for your tomato variety and climate.
The last step in regular pruning – topping your tomato plants.
Indeterminate tomatoes will keep growing and setting flowers, well, indeterminately. Until the first frost, that is. That’s why, when you know “winter is coming”, you should take measures and stop the plant from growing so enthusiastically.
In early autumn, we want our tomato plants to focus on ripening the fruit that’s already on the vine, instead of shooting up new growth and flowers that will never make it once the frost hits. So, 30 days before the estimated first frost, I top my tomato plants – which is exactly what it sounds, cutting their top growth off.
I’ve written in detail about what topping tomato plants entails, and you can check that article here.
After topping your tomato plants, you’ll still get suckers that you need to manage, but they won’t be growing at such a fast rate once the weather cools off.
Hopefully, you’ve learned how to make pruning your tomatoes a weekly habit. Don’t be too alarmed if you get off track. That early pruning work that you invested in early summer will pay off in autumn, even if you have some suckers sprawling over your plants.
If you do manage to stay on top of all suckers and top your tomato plants in time – congratulations! You’ve created a clean, tidy and abundant tomato patch for you and your family to enjoy!
P.S. If you’re looking to grow your tomatoes in a polytunnel, don’t forget to check these invaluable tips from my favorite Romanian grandma (oh, and activate those subtitles, too!)