I manage the growth of my tomato plants in order to keep them growing on one or two main stems. Left to their own devices, tomato plants will produce many branches, flop over, and become a tangled mess. This isn’t good for the condition of the fruit–it will rot more easily on the ground, and be more susceptible to insect pests and diseases–or for the quantity of fruit produced. If the plant is spending all of its energy producing extra branches and leaves it has less to spend on producing tomatoes.
By keeping the plants pruned to one or two main stems it makes it easier for me to keep them supported as they grow–and some of mine grow 10′ tall or more, so it’s an important consideration. I explain the best method I’ve found for that in the post Supporting heirloom tomatoes
If this idea of pruning tomato plants is new to you, please read the following explanation of how a tomato plant functions (the rest of you can skip down to the heading “Pruning Tomato Plants”)
The tomato in the above photo has one main stem.
Note the leaves growing off the sides of that stem–the plant needs leaves in order to take in sunlight and convert it to energy so that it can grow. Leaves will never bear fruit but they’re an important part of enabling fruit production.
Near the top of the plant you can see a fruiting branch–this is where the plant produces flowers that get pollinated and turn into fruit (i.e. baby tomatoes).
Between the main stem and the leaves there are suckers–these are the new bits of growth that, if left alone, will form additional stems (that will themselves sprout leaves, fruiting stems, and more suckers).
You might think that more stems would result in more fruit. This is true, to a point, but from everything I’ve read, if you have more than a couple main stems the plant spends so much energy growing the stem and the leaves on that stem that you actually end up with fewer and/or smaller tomatoes than if you kept the plant pruned. I like to think of pruning tomatoes as keeping the plant’s energies focused on producing tomatoes, which I can eat, rather than producing leaves and stems, which I can’t eat.
However, keeping the plant focused on fruit production takes diligence–it’s natural state is to send out as many suckers as possible. If you look at the photo below, I’ve highlighted four suckers ready to be pruned off this one little plant.
Pruning Tomato Plants
To remove a sucker you can just pinch it off with your fingers:
This is the best way to remove small suckers, as you want to cut it off as close to the stem as possible (i.e. not leaving any behind). Your fingernails can get into that small space much better than a pair of secateurs or scissors.
However, if the sucker is too big to pinch off easily, there is a risk that you could take a good chunk of the stem and outer “skin” of the main stem off. If the sucker you need to remove is that big, you’re better to use secateurs to cut the sucker out.
Tomato plants continue to keep sending out suckers as they grow. In order to keep them pruned to one or two main stems you need to examine them and pinch out any new suckers at least once a week. I really enjoy watching my tomatoes grow so I tend to wander into the patch every few days to see how they’re doing, pinch off any suckers, and wind the plants up the tomato supports. It’s one of the most pleasant parts of gardening for me.