close up of red tasty tom tomatoes

How Tomatoes are Grown in Highly Efficient Greenhouses

Knowing where your food comes from and understanding how it’s made, helps you understand your food even better. The science of our food starts at the farm, or even earlier, at the seed manufacturer. Even though a lot of food science doesn’t come into play once the food has been grown, it has a huge impact on your final product. Farming is where the science of our foods start and has a lot of influence on how they taste, react and behave. The science of farming is just as important!

So when we got the chance to visit a tomato greenhouse (and a pig farm) we jumped at the opportunity. Besides the fact that it’s simply fun to walk around in these businesses, it was fascinating to see scientific our food production has become. From controlling pests, to dosing the exact right amount of water to the plants, it’s fascinating and helps us to continue to feed the world.

Tomatoes in the Netherlands?

The tomato greenhouses we visited were in the Netherlands, a small country in Europe with a mild climate, including occasional frost and temperatures below zero degrees Celsius in winter. Tomatoes though, don’t like frost. They die when outside during those low temperatures.

Nevertheless, the Netherlands (and Iceland for that matter!) have a lot of tomato growers. Greenhouses protect the tomatoes and create an ideal climate for them to grow and thrive. In greenhouses there’s no frost and the tomatoes can grow year round. What’s more you can control light, moisture and temperature all very well, optimizing growing conditions. It’s one of the reasons the Netherlands is one of the major food exporters world wide.

Greenhouse is a mini-factory

The greenhouse we visited was huge. Despite me being used to large food producers, I was still amazed by the sheer size of it. Rows and rows of tomato plants. It’s a little factory, they’re really trying to optimize every little bit of production.

red tasty tom tomatoes in Dutch greenhouse
Rows and rows of tasty tom tomatoes. See the ripe tomatoes and the bottom and the green (and smaller ones) more at the top. Also look at the branches at the bottom which are horizontal instead of vertical. This is done on purpose, to lower the plants to reasonable heights.

Tomato plants grow up

What we noticed quite quickly is that there are a lot of horizontal tomato stalks in the greenhouse. Tomato plants grow best when growing upwards. However, the stalks are not strong enough to support the tomatoes. Therefore, the greenhouses use thread to guide the tomatoes upwards. Workers have to circle the plants around the thread regularly to assure they keep growing upwards.

However, since the plants keep on growing and since the greenhouse is only of a limited height, they have to go somewhere. Greenhouses have come up with an ingenious system for that. Instead of letting the plants grow higher and higher, from a certain point on wards, they lower the plants and move them to the side at regular intervals. That way long horizontal branches align at the bottom. The plant grows longer, just not taller this way.

This is possible due to the fact that on tomato plants new flowers (and thus tomatoes) only show up a the top of the plant. The lower half (that had flowers & fruits before) doesn’t get any new ones. This is especially true in a greenhouse where the leaves at the bottom are removed since they receive less sunlight. Once the tomato at the bottom has ripened and has been harvested, the stalk will stay empty from there on down, so can be lowered down.

Left: a tomato plant with green tomatoes on top and ripe red ones at the bottom. Middle: the tomato plant continues growing up. Right: the ripe tomatoes have been harvested, the tomato plant is lower and moved to the side to left the green tomatoes come down while ripening, the tomato plant remains the same height.

Greenhouses don’t use regular soil

If you look carefully through all those horizontal branches, you will notice that there is barely any soil in the greenhouse. Indeed, tomatoes aren’t grown in regular soil in most greenhouses. Regular soil is too variable for these greenhouses. The nutrients can differ, its consistency, etc. In a greenhouse they want to control everything as tightly as possible. They can control water, light, temperature, etc. so what not the soil as well?

Therefore they use a variety of commercial products. These help to only feed the plant the exact amount of water the plant needs. No water gets lost because it is drained away in the soil, instead, just about everything goes into the soil.

Tomatoes need a lot of water to grow, just like any plant and by optimizing the irrigation and water feeding, this greatly reduces the footprint of the tomatoes.

Tomatoes & bumblebees

And then there’s another optimization that seems to go quite in the opposite direction: pollination. In order for a tomato flower to grow into a tomato, the flower needs to be pollinated. In other words every flower needs to be touched which is a lot of work if you’d ask humans to do it. Automating this process using machines is also very complex. So growers have gone back to nature to look for a solution, which was ready for them to use: bees!

Bumblebees are the most suitable insects for pollinating tomatoes. Not only do they work the whole day long, even when the weather isn’t perfect. Also, once they’ve started pollinating tomatoes, they won’t be interested in other plants anymore, which makes them very faithful workers. They also do not look for nectar and barely sting people. This makes them very efficient pollinators for tomato growers.

Another benefit of using bees is that they are natural protectors of the tomatoes. They, together with several other insects, help prevent plagues and diseases of the tomato plants.

The bumblebees were indeed continuously flying around in the greenhouse. The bumblebees do need a home to go back to though, especially at night. This is why all around these greenhouses you’ll find boxes which are the homes for these faithful little workers. The doors of the boxes are such that they close down at night, preventing bumblebees from going out at night and getting lost and exhausted. They literally have a curfew!

tomatoes with bumblebee houses
The bumblebee ‘houses’ sit in between the plants so the bumblebees stay close around the plants.

Tasty Tom tomatoes

A lot of different tomato types are grown in the Netherlands, but we visited the greenhouse of a Tasty Tom grower. Tasty Tom is a licensed tomato variety, so there’s only a limited number of growers that grow them. The tomato variety defines the taste and structure of the tomatoes to a large extent. In the case of Tasty Tom tomatoes the tomatoes don’t grow that large, but they do contain a high amount of sugar, giving them a lot of flavour and taste. You don’t want watery, tasteless tomatoes, especially not in salads, where you eat them raw.

We learned that the Brix value of Tasty Tom tomatoes lies anywhere between 6,9 and 7,3 (Brix is a measure for the amount of sugar in a product). That means the sugar content of the tomatoes is about 7%, which is a lot higher than that of conventional tomatoes. The Brix value of those tomatoes lies around 4 – 5.

Position of tomato on branch matters!

The position of the tomato on its branch matters for flavour. Tomatoes grow in groups on one branch. The tomato closest to the main stalk of the plant actually ripens approximately one day before the tomato underneath, which ripens about one day before the one below, etc. Since these efficient growers only harvest a branch of ripe tomatoes, this means there is a slight difference in flavour between the tomatoes! The top one is actually slightly sweeter, than the one below! Even though all will become the same red colour, the flavour difference remains.

When growing your own tomatoes, or harvesting them one by one, you won’t have this problem of course. You’ll always pick the ones that are ripe immediately and leave the one that aren’t ripe just yet.

Cooking with tomatoes – Adding sugar

When making a sauce from tomatoes you will often be told to add sugar to the sauce. Tomatoes are slightly acidic from themselves (the pH-value is about 4-5). By adding some sugar you reduce the tartness and neutralize the overall flavour (it’s what makes tomato ketchup). However, take care in adding that sugar! The type of tomato you’re using greatly influences how much sugar you’ll need. If you’re cooking with these types of slightly sweet tomatoes, you’ll probably need a lot less (or none at all) sugar!

Storing Tomatoes

As we’ve discussed when talking about fruit & vegetable packaging and storage, not all fruits and vegetables should be stored in the fridge. Tomatoes are a great example of this as well. Tomatoes will keep longer in the fridge. The low temperatures will slow down the respiration of the tomatoes, which slows down deterioration processes. However, there is a major disadvantage of storage in the fridge: tomatoes have been shown to lose a lot of flavour in the fridge!

Therefore, despite the fact the will keep a few days extra in the fridge, it’s not worth it. Most tomatoes stay fine at room temperature for at least a week (depending on the quality when you bought them) and stay certainly have a lot more flavour as well.

Sustainable food production

Because of these tomato greenhouse being so efficient, it is a pretty sustainable form of food production. Even more so if you also use renewable sources of energy to control the temperature in the greenhouses! And if you do so, you can even grow tomatoes well in Iceland as this video below shows! (This is a 360 video, so use your mouse to turn the video around and literally look into the whole greenhouse!)

Sources

A research group investigated what happens in tomatoes during storage after harvesting.

Grodan, link ; an example of a supplier of greenhouse ‘soil’.

The website of the Tasty Tom producers we visited.

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