Udkansk v/ Nanna & Frederik

03 Jun 2021 12:02

How to grow and take care of tomatoes

At home, we love tomatoes!

Until this year, we have grown tomatoes on the window ledge and outside, but this year we will have tomatoes in our new greenhouse - something we have both been insanely looking forward to.

There is nothing better than stepping into a greenhouse and feeling the scent in your nose from the red clusters that hang down so nicely from the vigorous plants. And is there a better feeling than taking a big bite of a fresh, firm, freshly picked and tasty tomato?

For us, the tomato is without a doubt the uncrowned queen of the greenhouse. It, therefore, felt almost like a natural law that we should have tomatoes in the greenhouse.

Guide to growing tomatoes

If you, like us, want to start your tomato adventure from seeds, a rule suggests that you sow them 8 to 10 weeks before transplanting. It is therefore a good idea to start already in March, so you are ready to transplant in mid-May if you have a greenhouse, otherwise, if outdoors, from June. Tomato plants are heat-demanding plants, so keep an eye on the weather, the night temperature should not be below 10 degrees.


  1. Germinating

The reason we germinate in advance is that tomato plants are slow to get started. Therefore, we sowed seeds from March to April, in individual cells or small pots in good sowing soil.

After sowing, the seeds are placed on a warm and bright window ledge. Tomato seeds germinate best at 22-24 degrees, so room temperature is ideal to kickstart the germination process. You will see the small sprouts peeking out approximately 10-14 days after sowing. During the germination process, it is important that the soil never dries out. In terms of light, one should select the sunniest window to avoid tall and thin plants. When the germination is well underway, the irrigation should be adjusted so that the soil is kept moist but never wet. Imagine a slightly damp cloth, this is how the soil should feel.


  1. Repotting

The first leaves any seed unfolds are called cotyledons. These leaves are part of the start of any seed. The cotyledons generally do not have the same appearance as the common foliage of the plant. Tomato leaves are laciniate, whereas the cotyledons are oblong and oval in shape.

As soon as the tomato plant has formed 1-2 sets of leaves, the plant is ready to be repotted. Carefully lift the plant by holding on to the stem while loosening the soil underneath with a fork. Then move the plant to a slightly larger pot, where this time you use ordinary nutrient-enriched potting soil. It is important that the roots are damaged as little as possible during the move. Repotting is important so that the plant can continue its development. If the plants are left standing in the small seed trays in the nutrient-poor seed soil, the development stops. Once the plants have been repotted, it is recommended to shield them from direct sunlight for 24 hours so that the roots just have time to re-establish the absorbency. Always remember to irrigate after repotting plants!

  1. The outdoor life

From the end of April, you can start hardening the plants. The plants can come on a daily visit to the greenhouse or in a sheltered place in the garden for a few hours daily. The stay is then gradually extended by a few hours each day. It is a good idea to shield the plants the first days from direct sun. It is important that the plants are put back inside in the evening, as the small tomato plants do not tolerate below 10 degrees as the nutrient uptake is disturbed and the plant gets stressed. After 7-10 days of getting used to it, the tomato plants can move into the greenhouse, if you grow in the outside, it is best to wait until early June, as it can still be cold in the open air at night.

  1. Caring

Tomatoes should not be transplanted in containers below 15L per plant. Capillary boxes work really well, otherwise, jars can also be used just fine. A good tip is to transplant the tomato plants 2-4 inches deeper than they were in the previous pot, as tomatoes can form roots from the main stem. This helps the plant to stand more stable in the container, as well as it helps the extra roots with water and nutrient uptake. Tomato plants grow fast and are greedy plants. They have a great need for irrigation and fertilizer. If you grow in capillary boxes, you can add liquid fertilizer directly into the water, if you plant in pots, you should fertilize at least once a week. Use a liquid tomato fertilizer that contains a high potassium content as this stimulates the flowering.

As the plant grows, it is continuously tied up on a plant support or similar. The tomato plant will try to put side shoots from the leaf corners, these should be removed regularly. We do not want the plant to waste its energy on forming a large number of leaves, but instead, we want it to concentrate its energy on setting flower clusters. Concludingly, I would like to quote my grandmother, who always said: "Tomatoes are like children, they thrive best with regularity and stability." My grandmother was right, tomatoes do not like large fluctuations, neither in terms of temperature, water, or fertilizer.




… Tomatoes have a high content of vitamin A and C.

… There is a Spanish tomato festival, Tomatina, where every year more than 120 tons of tomatoes are used.

… The tomato originates from South and Central America and came to Europe in the 16th century.

… In Europe they did not start eating tomatoes until the 18th century because they thought the fruits were toxic.

… From a botanical point of view, tomatoes are a fruit but it is sold as a vegetable.

… There are more than 25.000 different tomato sorts.

… Tomatoes value chalky tap water, as it helps prevent blossom end rot.

The origin of the tomato

The tomato is with its cousin, the potato, one of the most widely grown vegetables in the world. They both belong to the nightshade family, Solanaceae, which consists of a few thousand different species. Several of them are edible, while others are extremely toxic. Some are used exclusively as ornamentals, such as the summer flower Petunia.

Although the Italians are world-famous for the use of tomatoes in their cooking, the fruit originated in South America and was imported to Europe back in the 16th century during the colonization of South and Central America.

The plant thrives in tropical environments where the soil is moist and nutrient-rich, which is exactly those conditions we try to recreate in our greenhouses. The tomato plant does not make tendrils, such as peas. In the wild, the plant is creeping and will twine around and up other plants to better present its small yellow flowers to pollinating insects. This is of course a bit space consuming in the greenhouse, so therefore we support them in growing vertically.