A Guide to Topping Tomato Plants: How, When, and Why?

Topping tomato plants is an essential part of the gardening calendar, and it’s not a one-off! From early summer, right through to harvest, topping tomatoes keeps your plants in check, and helps to produce more reliable harvests. But! There are some really big mistakes you can make, so let’s take a look at exactly what to do, and what not to do when topping tomato plants.

Timing, height, variety, and location will all affect how and when you top tomato plants. Most importantly though, not all tomatoes need topping. Determinate tomatoes (those with pre-determined growing heights), also called bush tomatoes, don’t need topping at all. Indeterminate, or cordon tomatoes, are a constant battle to reign in their height.

What is topping tomato plants?

Topping tomato plants is as simple as it sounds; cutting off the tops of tomato plants. There are, however, a few different methods. My preferred method is to top off cordon tomato plants when they reach around 6ft, and then keep on going. 

Cutting back to the top growth of tomatoes every few weeks makes sure that they focus their energy on the developing flowers and fruit below, without wasting time growing new trusses at their tips. 

Topping tomato plants Vs pinching out tips

You might also have come across the term ‘pinching out tips’, or ‘pinching tomato tips’. This is done to pretty much all young tomato seedlings to encourage lateral growth, and it is more of a choice than a necessity. 

In short: pinching out tomato tips promotes more productive, but shorter plants, and is done early in the growing season; topping tomato plants stunts growth, and should be done throughout the growing season. 

Note: Pinching out can also refer to pinching out side shoots and suckers. This just means removing the diagonal shoots between the truss and main stem and should also be done regularly throughout the season.

The benefits of topping tomato plants

Before I go into detail about the benefits of topping tomato plants, there are some negatives, depending on where you live, and how you grow tomatoes.

But, with that short list of negatives aside, nearly all other outcomes are positive, and avoiding the negatives is all a matter of good tomato management.

Topping tomatoes produces bigger fruit

The most obvious advantage of topping tomato plants is bigger fruit. By topping tomato plants regularly, you are focussing their energy on the flowers and fruit they have already begun working on. 

That means more water for the fruit lower down, and more nutrients to share between existing tomatoes.

Topping tomatoes leads to more even ripening

If you plan on making batches of tomato ketchup, pasta sauces, or soups, topping off indeterminate or cordon tomatoes regularly can help them ripen more evenly. Remember, cordon tomatoes will keep trying to grow, and continue producing new fruit until the plant dies. 

If you top the plants so to around 6ft, more fruit will ripen all at once, producing a tighter harvest window for all that batch-cooking joy!

Topping tomatoes provides better air circulation and ventilation

Any pruning, whether it’s pinching out suckers, or trimming the low growth at the base of tomatoes, helps to improve air circulation, and will allow light into the plant. Better ventilation reduces diseases, and more sunlight helps to ripen fruit faster.

Topping tomatoes makes them easier to train

As well as making tomatoes easier to train, topping tomatoes also reduces the weight of plants and the burden on your supports. Trellis, twine, tomato cages, and tepees, are all great ways to support tomato plants, and topping tomato plants keeps them in check so they don’t outgrow their supports.

If that’s the only reason you decide to top your tomatoes, it’s a good one.

How to top your tomato plants

OK, so we know why we top tomato plants but how, exactly, should it be done?

Well, that depends on where you’re growing them, and the reason for topping them. In cooler climates, the aim of topping is to reduce new growth and improve ventilation. In warmer climates, it’s to reduce disease and help train them.

Topping tomato plants in cool climates should be done every two to three weeks, whenever there is new growth at the top of the plant. To reduce how often you do this, there’s a right place to cut, and a wrong place:

In warm climates, topping tomatoes is all about disease control and training. There’s no right way or wrong way to do it, but it’s often only necessary to top tomato plants in zone 9-11 when they reach 8ft, and the weather begins to cool right down. Cut below a node, as above to reduce re-growth and focus energy and light on ripening fruits.

When to top off tomato plants?

In really warm climates, tomatoes can continue growing into winter and will crop in a repetitive cycle. For me, in my chilly northern spot, my tomatoes tend to stop ripening around late October, when the sun begins to drop and the days are dramatically shortening, so allowing any growth above 6ft at any point in the year is simply counterproductive.

Top tomatoes when they reach 6ft in cool climates (zone 8 or lower)

In cool climates like ours, topping tomatoes should be a fortnightly task. If they ever exceed 6ft, the chances are, that fruit won’t ripen in time for harvest. 

The cooler afternoons here even in summer mean that every drop of sunlight is needed to ripen fruits too, and anything over 6ft will shade out other plants, and the fruit lower down.

Top tomatoes if the greenhouse becomes too humid

If your greenhouse begins to exceed humidity of 75%, there’s a heightened risk of blight and other fungal problems. Removing the top growth on any tomato plant will reduce shade, and increase the heat, helping to decrease trapped humidity, and improve ventilation.

Humidity sensors are indispensable tools and can be picked up for next to nothing online.

Top tomatoes when the days begin to shorten

After the summer solstice, when days begin to shorten to less than ten hours of sunlight, any undersized fruit is unlikely to grow further and certainly won’t ripen. 

Remove any tall trusses, in the fall, and top your plants just below a node to discourage regrowth. This will speed up the ripening of lower fruit.

Top tomatoes ahead of frost

If you’re lucky enough to grow tomatoes in zone 9 or above, tomatoes can and do, continue cropping well into November, even early December in some Southern regions. But, if frost is forecast, it’s time to top your tomato plants one last time, and close any greenhouse windows to conserve heat. As soon as the plants begin to wilt, harvest any remaining fruit and ripen it indoors.

How NOT to top your tomato plants?

Now you know how and when to top tomato plants, make sure you’re not making any of these simple mistakes:

Takeaway

There are no climates where topping tomatoes isn’t necessary at least once a year. Follow our guide, and adapt it to your own growing conditions, remembering that greenhouse tomatoes have different needs to outdoor crops, and determinate or bush tomatoes don’t need topping at all.

Crucially, topping tomatoes is part of a wider routine of caring for tomato plants, and shouldn’t be used as the be-all and end-all. If you’re planning your planting for next year, check out our guides to growing tomatoes in grow bags, how to train tomatoes, and how to prune them all year round, before getting to grips with how to top tomato plants.