Growing Tomatoes – Greenhouse efficiency

Knowing where my food comes from and how it’s made, is something that makes me understand my food even better. It’s where the science of our foods start and has a lot of influence on how they taste, react and behave. So when a Dutch supermarket held their ‘visit the farmer’ days I joined and visited two farms close by to us: a pig farm and a tomato farm!

Besides the fact that it’s simply fun to walk around in these businesses, it was fascinating to see how our food is made, how efficient and well thought through. Therefore, I’d really like to share my experience! So today, no cooking or science of cooking, but we’ll be farming! Growing tomatoes!

Tomatoes in the Netherlands?

 

Tomatoes don’t like frost, they die when outside during on night with frost (I’ve had the unfortunate honour to experience it first hand with my tomato plant which went outside just a little too early in the year…). Then why would the Netherlands have a lot of tomato growers? That’s where greenhouses come in, the Dutch are known for their efficient food production in tomatoes. It’s not just tomatoes, but we sure have a lot of those.

In greenhouses there’s no frost and the tomatoes can grow year round. What’s more you can control light, moisture and temperature very well, optimizing growing conditions.

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 tomatoes ready for processing. The Brix value of those tomatoes lies around 4 – 5.

Position of tomato on branch matters!

One of the most interesting facts I learned is that 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 you have have 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 neutralise the overall flavour. 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.

Greenhouse is a mini-factory

The greenhouse we visited is huge, despit 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, this is due to the process of lowering the plants as described below.

Tomato plants grow up

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.

New flowers (and thus tomatoes) show up a the top of the plant. The lower half (that had flowers & fruits before) doesn’t get any new ones, especially in a greenhouse where the leaves at the bottom are removed since they receive less sunlight.

However, since the plants keep on growing they have to go somewhere and they’ve come up with an ingenious system for that. Instead of letting the plants grow higher and higher, they will lower the plants and move them to the side at regular intervals. That way long branches form at the bottom, whereas the plant doesn’t effectively grow any higher, just longer. This also helps to keep all the ripe tomatoes at a convenient height to be picked.

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

Tomatoes aren’t grown in regular soil in most greenhouses. Regular soil is too variable for these greenhouses. Since everything can be controlled in greenhouses (water, light, temperature), they need ‘soil’ which can be controlled very precisely 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

There were so many interesting facts we learned during this visit to the greenhouse, but I’ll share just one more: bumblebees. In the greenhouse we visited barely any insecticides etc. were used, instead, natural protection of the tomatoes was uesd. They have several insects they use to fight plagues or diseases, to keep the tomatoes healthy. One of these are bumblebees.

Apparently bubblebees 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, which is nice since there still is quite a lot of handwork involved. This makes them very efficient pollinators for tomato growers.

The bumblebees were indeed continuously flying around in the greenhouse. They also have their homes installed all around the greenhouse!

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

Sources

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

An example of a supplier of greenhouse ‘soil’.

The website of the Tasty Tom producers we visited.

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