A tomato plant has clustersof little yellow flowers. Each yellow flower contains a pistil (the female sexual organ) and stamens (the male sexual organs). So a tomato plant has both male and female reproductive organs in its flowers. To get tomatoes, the yellow flowers have to be pollinated. That means that the pollen from the stamens ends up on the carpel.

In nature, pollination is done by insects that are looking for pollen, or by the wind. If you grow tomato plants outside, pollination happens automatically.

It’s another story when you grow tomato plants in a greenhouse. There is hardly any wind in the greenhouse and there are far fewer insects around, especially in early spring. Then it is a good idea to give nature a helping hand. You do this by tapping the clustersof yellow flowers 3 times a week. The vibration makes the pollen dustland on the pistil. Do this when the sun shines (so from 10:00 a.m. onwards), otherwise the pollen sticks and won’t get dusty.

It’s not that bad.Even in a greenhouse you will get tomatoes on the plants. However, a number of flowers will give no or very small tomatoes (they have no seed). It’s different for each tomato variety. The one has to be actively pollinated, otherwise no tomatoes will arrive, but the fruit of another variety will mature on the cluster without any difficulty.

At our nursery we put in bumblebees to pollinate the flowers. These diligent workers feed on sugar water because there is no nectar in the flowers of the tomato plants. The bumblebees will pick up the pollen from the flowers, and that’s how they pollinate the flowers.

In the past my father and grandfather did it all by hand. They called it ‘trembling’. The device they used had a vibrating pen. Trembling each cluster 2 to 3 times per weekwas a huge amount of work. I'm glad that the bumblebees do this for us now. 😊

Pruning is very important. Bind the tomato vinesto a stake about 2 meters long, jammed firmly in the ground. The tomato plant has a main stem along which grow the leaves, clusters of flowers and, later, the tomatoes. Going up the vine, between each cluster of yellow flowers there are sequential sets of 3 leaves. The plant continues growing like this until it dies. After a while a side shoot grows at the place where the leaf is attached to the stem. The leaf must remain in place, but the side shoot must be removed. It is important to remove all the side shoots. If you don’t do this, you will get a very large and full plant, with lots of leaves, but few tomatoes. And you can’t eat tomato leaves, so they’re no good to us. 😉

You can read more about pruning tomatoes in the article: "How do you get tomatoes on your tomato plant?"

With greenhouse tomatoes, watering can influence the growth of the plant. A plant that gets little water will give sweeter fruit and produce smaller leaves. Especially in the spring and autumn you can do well with this. If it is rainy or cloudy for a few days, do not water. This will force the roots to get stronger and the plant will put more energy into the tomatoes (making them bigger and sweeter).

Try experimenting with your watering. Don’t overdo it; it’s not the intention to let the leaves of the plant go limp. In summer, when temperatures are high, a tomato plant consumes a lot of water and you should water them daily.