What do you need?
- Tomato seeds
- Potting soil
- Pots or seed trays
This cultivation advise is provided as a general indication only. These are not definitive growing instructions and may need to be adapted to your local soil and environmental conditions.
It is best to sow tomato seeds indoors in spring or even earlier. As a general rule start sowing 6 - 8 weeks before it's time to plant tomatoes in your garden or in pots. In general this will be in Europe in March / April. Tomato plants are warm season crops.
Sow the tomato seeds in moist potting soil and cover them with a maximum of 0,5 cm of soil and spray some water on it. Don’t sow to deep. Otherwise the seeds do not have enough energy to reach the surface.
Tomato seeds germinate best at a temperature of 23 - 26 degrees Celsius. If the temperature is too low, they will not germinate and stay dormant.
The seed trays, you can buy in garden centers, often have a lid. This will create a humid environment which the seedlings love. You can also use ordinary flower pots and cover them with cellophane. Make a few small holes in the cellophane using a needle for the supply of oxygen. Do not forget to label the tomato seeds to know which variety you’ve sown. It’s a pity to wait for months to finally be able to identify your chili plant. Place the seed tray or pots on a warm spot.
That can be in the sun, in a heated room or near a radiator to ensure optimal conditions for germination. There are also heated propagators for sale that accelerate germination. At this moment there is no need for light, but only for heat, moisture and oxygen. Keep the soil moist but not wet, otherwise it’s possible that the tomato seeds may rot. Prevent fungi by ventilating the system occasionally. Fungi can kill tomato seeds and seedlings.
Wait for 7 - 10 days for tomato seeds to germinate. Sometimes germination is even faster.
The seedlings are sensitive to their environment and now not only benefit from heat, moisture and oxygen, but mostly of light. The plants love high light conditions. If there’s not enough light in your house a plant grow light may be a good investment. When the seedlings have formed a second set of leaves you can repot them. Remove the plants and their root ball out of the soil without damaging the roots and put it in a larger pot with soil. Now the plant has more space to grow. You can repeat the repotting when roots are appearing through the drainage holes at the bottom of the pots.
Once the plants are strong and big enough, you can put them outside in pots or plant them in the garden (around May in northern Europe) when the weather is nice. Be aware! The plants should be hardened off, which means that they have to get used to their new environment (different light, wind, heat). You can consider to put them outside for a few hours and later take them inside again to slowly acclimate to the new environmental conditions.
Do not put them directly in the sun to prevent sunburn. If the plants have grown significantly and tend to hang down, you can support them with bamboo sticks.
In summer the first flowers will appear on the plant, the first sign of tomatoes. You can feed the plants with a fertilizer, like liquid tomato fertilizer, to grow full fruits. After pollination of the flowers the tomato will grow. The flowers will drop and the tomato emerges.
Indeterminate versus determinate
The indeterminate tomato is the largest group of tomatoes and are usually pruned (see pruning and topping). The plant grows until it dies because of frost or disease. In warm countries the tomato plant can easily keep on growing. The growing season is longer there and the tomato plant is not always pruned.
In countries where the growing season is shorter, as in Northern Europe, we want the plant to maximize its energy on the growth and maturation of several trusses of tomatoes. This is achieved by pruning the plant and eventually top it.
Pruning a tomato plant is easy. In each leave axil a side-shoot (sometimes called sucker) is produced. We can remove the side-shoots with scissors or with the fingers, to ensure that there is only a main stem without side branches. If we don’t remove the sideshoots they will keep on growing and eventually produce flowers and tomatoes. This will cost the plant much energy, energy that’s better used in our climate for the growth and maturation of several trusses. These trusses will therefore grow larger and are ripe in time just before the plant dies of the first frost.
Often the tomato plant is topped after the fourth or fifth truss. The top is simply removed after the last two leaves above the last truss. One reason to stop the plant from growing is that it’s unlikely that future fruit in our climate will still ripen in August and September.
Indeterminate tomatoes are larger than determinate tomatoes and can grow meters high when they are not being topped. Indeterminate tomatoes should be supported with bamboo sticks or cages.
Determinate tomatoes (or bush tomatoes)
Determinate tomatoes stop growing themselves. Unlike indeterminate tomatoes which produce tomatoes throughout the season, determinate types produce tomatoes in a short period, all at once. Determinate tomato plants don’t need to be pruned, remain relatively small and have a shrub-like appearance. Many determinate tomatoes are perfect for growing in pots on a patio or balcony.
The determinate tomato is often smaller than the indeterminate tomato.