How to Prune Tomato Plants For EXPLOSIVE Growth (the Right Way!)

It’s usually recommended to remove all sideshoots (also known as suckers) from vining or cordon tomatoes – and we’ll look at why that is in a bit – but for the very biggest harvests you may actually want to leave a few of them to grow. So I’m going to show you exactly how I prune my tomatoes to help grow the healthiest plants and give the best results...

Improve Airflow

I grow tomatoes two ways: in the greenhouse, supported by strings hanging from the roof; and out in the garden, tied at regular intervals to upright canes.

I’ve learned the hard way to grow only blight-tolerant tomatoes outside. Too many times I’ve been within a whisker of a hefty harvest, only to lose all those hard-won fruits to this ruthless disease! And this is one of the first reasons to prune tomatoes – to remove excess foliage so that more air and light can reach all parts of the plant, which is super important if you’re growing your tomatoes close together. This in turn reduces the risk of disease – not just blight, but other diseases like fusarium wilt, mildew and septoria leaf spot.

For me, pruning starts at the bottom of the plant. First I remove any leaves that are touching the soil. Wet leaves are a danger point for disease, so removing ones in contact with the often-damp ground greatly reduces the risk. Then, as plants grow I like to remove all of the lowest leaves, right up to the first developing truss of flowers or fruits. This gives several inches of clear stem, minimising splashback from the soil at watering time or when it rains. It also enables air to circulate better so leaves dry faster, making it much harder for fungal spores to establish.

It also means I can fit in some lower growing plants at the base of my tomatoes to make even more of the space I have. That might be salad leaves, basil, or companion flowers like marigolds.

Pruning Tomato Suckers

The next thing to prune are the sideshoots, or suckers. Leafy side branches sprout from the main stem, but between the leaf and the stem, at about a 45-degree angle, grow suckers. I like to think of suckers as growing in the ‘armpit’ of the leaf-stem union!

If we leave the sucker to grow it will produce another full-on stem, producing more leaves and suckers of its own. This would create more of a bushy plant, so to ensure good air circulation in tighter spaces like greenhouses we want to remove them. The simplest way to do that is just to click them off between your finger and thumb. Check your vines every couple of days and nip off any new ones each time.

If you’ve missed one that’s grown a bit bigger, cut it off with sharp knife or pruners to avoid any risk of tearing the main stem. If you’ve noticed any tomato diseases on your plants, it’s good practise to wipe the blade between plants with something like isopropyl alcohol to avoid transferring diseases between plants.

Removing suckers keeps sky-bound tomatoes growing as a single stem, which means we can grow plants more closely while still enjoying good airflow and light. In the greenhouse I grow several different varieties side-by-side, so pruning means I can enjoy a range of different tomatoes without taking up loads of space. If I didn’t prune out my suckers, not only would my tomatoes become an overcrowded, difficult-to-manage tangle, but the roots would need to expend a lot of energy to support all that leafy growth at the expense of flowers and, ultimately, fruit.

So by removing those suckers, my tomatoes have no option but to do two things: continue growing upwards from the main stem, and produce trusses of flowers and fruit. By concentrating our plants’ energy onto flower and fruit production, we’ll get those first tasty toms a lot sooner. That’s really important in cooler climates with shorter growing seasons like mine. So long, suckers!

When Not to Remove Suckers

So if removing suckers gives fruits earlier in the season and ensures better airflow, when should you not prune?

If you have more space between your plants then you could try leaving one or two suckers grow (making sure to support them) and produce fruits of their own. This will produce a multi-headed tomato plant that will have the potential to produce many more fruits on the same plant. It's a great way to make individual plants go that much further, and stretch budgets by getting more from your plants.

Another reason to leave some suckers in place is to shade slower-growing fruits from harsh sunshine to prevent sunscald. This is not so much of a problem in my cool climate, so it’s not an issue I’ve personally experienced, but in very hot climates it may be something to consider. You could always prune the suckers to keep them to a manageable size if you need to, just retaining enough leaves to shade those fruits.

Another reason to leave at least some suckers would be to produce more fruits further up the plant. This summer is winding up to be one of the warmest on record where I live, which means I’m getting growth rates more often associated with Mediterranean regions. It’s still early summer right now, and the vines are just about reaching the top of the greenhouse. With at least another two and a half months of summer left, I’m running the risk of the fruits setting much earlier than usual but then leaving little else to look forward to.

So what I’m going to do is allow maybe three or four suckers per vine to develop and produce one truss of fruits each. I’ll then nip out the growing point at the top of the sucker beyond the truss, which will limit any further growth so that that the fruits on each sucker can swell and ripen in good time. That means I should enjoy more tomatoes from each plant than I might otherwise have had without compromising air circulation too much.

If you’re in a warm climate with a nice long growing season, you may find that pruning isn’t really necessary at all! Plants will grow very vigorously and will have plenty of time to ripen all fruits that are produced. Having said that, I’d still recommend pruning off lower leaves to enhance airflow, because fungal diseases can be a real challenge in hotter regions.

‘Stopping’ Indeterminate Tomatoes

The main, central stem of indeterminate (a.k.a. cordon or vining) tomatoes can grow on and on…and on! In commercial greenhouses they’re left to grow to epic heights, reaching near the top of the glasshouse and then often looping back down again like great big jungle vines.

But for gardeners this isn’t usually a great idea. One final bit of pruning you can do is to ‘stop’ cordon tomatoes by simply pinching out the top of the main stem when it reaches the top of supports or the roof of the greenhouse. This will reroute the plant’s energy into forming and ripening fruits instead, and avoids fruits produced high up on the plant that won’t have time to ripen before the first frosts.

Grow New Plants For Free From Tomato Prunings

If you’re in a warmer climate than mine, with a longer growing season, you could make good use of pruned-out suckers by growing them into new plants. Remove most of its leaves then either pop it into water, or plant it up into a pot of multi-purpose potting mix. Once you see roots or new growth, plant it as you would any other tomato. It will grow really quickly into a new plant. This is a very nifty way to propagate new tomato plants for free and boost your harvests for the second part of summer and on into autumn.

Pruning Determinate Tomatoes

Determinate (bush) tomatoes are super simple to grow. Pruning would actually reduce fruiting on these kinds of plants because the fruits are all produced at the end of each sucker or stem. The only pruning I’d recommended would be to remove the very lowest leaves to give a stretch of clear stem at the bottom of the plant to reduce splashback and the risk of disease.

And honestly, that is it. So if you still don’t like the idea of pruning, bush tomatoes could be for you!

Plants Related to this Article

Tomato (Cherry) Grow Guide

Tomato (Regular) Grow Guide