Now is a good time to think about pruning – bush varieties don’t need pruning but tall varieties do. This is the way I like to prune my tall (aka cordon and indeterminate), tomato plants.
Leaf Pruning – please read carefully before chopping!
It’s a good idea to remove leaf branches up to the first truss when the first truss has started to set fruit. However, it is important to understand that the closest leaf branch to each truss of fruit, provides the tomatoes on that truss with the energy they need for growth and taste.
In other words, each leaf branch provides energy for its nearest truss.
This is important to keep in mind when we are removing leaf branches if we want maximum growth and taste.
Remove the middle branch when plants are too vegetative (leafy)
For example, if there are three leaf branches between the first and second trusses, the best way to prune is to remove the middle leaf branch, leaving the branches nearest the trusses.
It’s good to keep leaf branches below and above each truss as the fruit are swelling, but once the tomatoes have begun to ripen, all the leaf branches up to that truss can be removed.
We want energy to go into fruit production – not making a lot of leaves!
Leaves below the first truss
Below the first truss, leaves lose their colour early because the growing tip removes their nitrogen and magnesium etc. – the growing tip gets preference! All the leaf branches can be removed (gradually) up to the first truss when the tomatoes on the first truss have started to set fruit.
The second truss and above
Removing all of the leaf branches up to the second truss can be done when the fruit on the second truss is ripening (not just setting). In other words, leaf branches can be removed up to the truss that is producing ripe fruit.
By this time, the ripening fruit will have received plenty of sugars from their nearest leaf branches.
Four of Five Trusses Outside
If you are only growing four or five trusses, I wouldn’t worry too much about removing all branches up to the ripening truss – just remove leaf branches up to the first or second truss, middle leaf branches as fruit are swelling, and trim long leaf branches if necessary.
You may wonder why we need to prune at all?
It’s because we need to keep a balance of leaves/fruit and keep a plant producing enough energy from the leaves to supply to the fruit.
Tomato plants have two phases of growth
- The vegetative phase – producing the stems and leaves etc.
- The generative/reproductive phase – producing the flowers and fruit .
The plant begins its life in the vegetative phase and when flowering and fruiting begins, it moves into its reproductive phase.
However, these phases are not mutually exclusive – in the second phase of flowering and fruiting, we still want plants to be growing stems and leaves to support higher trusses, but the main objective is to provide enough energy for the continued growth of the plant and tomatoes over a given period of time. This means that a balance of vegetative and reproductive growth is required.
This is where pruning comes in … also known as plant steering.
We want to direct energy from the leaves to the fruit. We don’t want to create a lot of big luxurious fat juicy leaves that when they get a bit older will become a drain on the plant’s energy and reduce the amount of tomatoes we get! By the way, tomato leaves are poisonous – don’t eat them!
Check your trusses
One way to tell if your plants are too vegetative (apart from having lots of leaves) is by the position of the trusses.
If your flower trusses are pointing upwards, the plant is probably too vegetative. If a truss is roughly at 90 degrees, that shows a balanced growth.
Leaves in shade are less important
For example, if you are growing plants up against a wall or fence, the leaves at the back will be producing much less energy for the plant than those at the front in direct sunlight, so shaded leaves can be removed (as long as there are enough leaves at the front of course!).
Feeding large tomato varieties
If you’ve ever tried to grow large tomato varieties that run out of steam at the second or third truss, it’s probably because the vegetative and reproductive balance needs adjusting. We tend to overfeed with with potassium (tomato food) too early which slows growth and encourages ripening. Using a balanced feed will help keep growth in the upper trusses.
The method above is the way I prune and feed my tomato plants. There are no rules set in stone but by following a few tips about pruning, you should improve both the growth and taste of your tomatoes.
Another week has past and tomatoes are on their way!