I’ve written about this subject before, but I keep getting so much feedback on the subject I figure the information is worth repeating. And what I’ll try to get across here—hopefully more clearly this time around—is that you don’t necessarily need to remove tomato suckers … and, in fact, you can’t, because tomatoes don’t produce suckers. And you can’t remove something that doesn’t exist, can you?
A sucker is, by definition, a stem that never produces either flowers or fruits. Logically, you’d want to remove suckers from your tomatoes if they had any.
The thing is, though, they don’t. Those green stems that start to form at leaf axils (see the photo above) are not suckers, they’re simply secondary stems. Branches if you prefer. Left to grow, they will produce both flowers and fruit… and therefore aren’t suckers. Studies show that tomatoes whose side stems are left in place produce more fruit than ones whose secondary stems are removed, although the fruit may be somewhat smaller. Still, there is a net gain in total tomato production by weight, so you get more “tomato” to eat by not pruning… sometimes considerably more.
Suckers Drain Energy, Stems Provide It
It’s important to understand that, as the word “sucker” is clearly pejorative. When you hear it, you automatically imagine the sucker stealing energy from the plant. It sounds like something you should get rid of. On the other hand, the word “stem,” the true term, is a neutral word, neither negative nor positive. You have to ask yourself what is the advantage of removing a stem from a tomato plant.
And here’s the really important point: since stems produce leaves and leaves carry out photosynthesis, stems don’t “suck” the energy out of the plant. Instead, they provide energy. All the energy of most plants comes from photosynthesis and photosynthesis is carried out by the green parts of the plant. Since these secondary stems are not only green, but bear leaves, they add considerable energy the plant can use to grow more vigorously and produce more fruits.
Yes, tomato plants will actually be stronger and grow more vigorously if you don’t prune off the secondary stems. It’s as simple as that!
Why Then All the Insistence on Removing “Suckers”?
Generations of gardeners have been taught that removing secondary stems from tomatoes is important. In fact, the practice is now so firmly entrenched that most people just do it, without ever questioning why. But there is a reason people first started doing it… and here it is:
When a tomato plant is grown on a stake in order to keep it from sprawling rather than on a trellis as had been the method used before the 20th century, there is a limit to the number of stems that can be attached to the support. Our ancestors decided to remove the secondary stems in order to better attach the plant to its stake. If you use a single stake, traditionally you’d keep only the main stem and remove all the others. If you use two stakes (a fairly common technique), a second stem is allowed to grow and produce fruit while all others are removed.
So, the reason behind removing secondary stems never had anything to do with improving the harvest, but rather was strictly a question of staking the plant in a logical manner.
When tomato cages first began popular towards the end of the 20th century, that changed the situation. As they support the plant on all sides, removing the secondary stems is no longer necessary: there is a structure around the whole plant that can hold up even the lankiest stem. As soon as any stem starts to grow outside of the cage, simply push it back inside. It couldn’t be easier! Except that most gardeners continue to remove secondary stems even on caged tomatoes without even asking themselves why.
Of course, typical tomato cages are designed for determinate tomatoes, which are relatively small plants. To support an indeterminate tomato, like the popular and very vigorous cherry tomato ‘Sweet 100’, a huge plant with multiple stems, takes a large tomato cage. They are less common, but they can still be found in better garden centers or you can make your own.
So there you go: if you’re using an appropriately sized tomato cage, you no longer need to remove any secondary stems.
The Advantage of Pruning Secondary Stems
There is, however, one advantage to removing secondary stems. As the plant will now produce less fruit, it will put a little more energy into its reduced crop and each fruit will be slightly larger.
The Advantages of Not Pruning Secondary Stems
If you don’t remove secondary stems, you will usually harvest about twice as many tomatoes, although they will be slightly smaller than the tomatoes produced by a pruned plant. On the other hand, they often taste better because the plant has more leaves and therefore more energy… and leaves convert solar energy into sugar.
Also, pruning tomatoes leaves a wound that harmful microbes can use to penetrate your plant, something you avoid if you don’t prune. If you do decide to remove the secondary stems, make sure you sterilize your pruning shears between each cut. It’s very easy to accidentally transmit diseases, notably viruses, from one tomato plant to another.
Obviously, though, the biggest advantage of not removing secondary stems is simply that it requires less effort. Long live laidback gardening!
A Few Misconceptions About Pruning Tomatoes
Some gardeners claim that letting all the branches grow will delay the harvest, but in fact, it really has no effect on maturation. The variety of tomato, the growing conditions, the weather and other factors do influence the speed at which tomatoes mature, but not pruning. An unpruned tomato plant will produce fruits as quickly as a pruned plant, sometimes more quickly. After all, it has more energy to put into it.
Other people claim that tomato fruits must be exposed to the sun in order to ripen and therefore on a pruned plant, with reduced foliage, the fruits will be less likely to be hidden by foliage and thus the fruits will ripen faster. But in fact, this is not the case either: even fruits that are completely hidden by leaves ripen perfectly well. It’s the leaves that must be exposed to the sun, not the fruits. Worse, fruits suddenly exposed directly to full sun as a result overzealous pruning can suffer from sun scald and becomes essentially unusable.
The gardeners in cold climates often insist they have to prune their tomatoes that because of their short growing season. They’re convinced that tomato plants whose secondary stems are removed will mature more quickly. I repeat, the more green leaves a tomato plant has, the more energy it will have … a big advantage when your growing season is short.
(There are ways to get tomatoes to mature more quickly in short season climates, notably by choosing extra early or cold-resistant varieties, growing them under cover to keep cold air away, fertilizing well, never letting the root system dry out and removing any late-season flowers that won’t have time to produce mature fruit. Removing healthy stems and foliage is not on the list.)
Do Remove Yellowing Leaves
No matter whether you grow tomatoes staked or in a cage, pruned or unpruned, it’s always wise to remove yellowing and dead leaves. They no longer contribute to the growth of the plant and can harbor diseases.
To Prune or Not to Prune?
Now that you know a little more about the situation, it’s up to you to decide whether you want to remove your tomato’s secondary stems so you can tie it to a stake or grow it inside a cage so you can forget about pruning entirely. Personally, I switched to tomato cages years ago and never prune healthy stems. Most years we end up with more tomatoes than we know what to do with… on only two plants!