Planting tomatoes in the greenhouse

Unfortunately, there is no good harvest guarantee for tomatoes (Solanum lycopersicum) outdoors. In the greenhouse the warmth is right and the rain is denied access, so that tomatoes feel good. With the right care, cultivation is a sure-fire success.

Suitable greenhouse

Every tomato plant is happy about a large glass greenhouse. However, it is not a must for covered cultivation. Tomato houses made of foil are also available in stores. Their lifespan is shorter, but they are comparatively very cheap. Smaller of them are even suitable for growing tomatoes on the balcony. Your own construction can also be built inexpensively. It is sufficient if it has a translucent roof and three sides. The ideal location for the greenhouse is in a sunny location, as tomato scientifically loves and needs warmth.

Planting time

Outside, tomatoes are not planted until mid-May. This planting time also applies to greenhouses that are not closed on all sides. Because even low temperatures can destroy tomato plants. In the glass greenhouse you can plant tomatoes around mid to late April. The young plant should then have a height of about 20-25 cm and the first flower cluster should be visible.

Tip: Instead of buying young tomato plants in stores, you can also bring them forward at home from around mid-February. Either in the house on a warm and bright window sill or in the greenhouse, if it can be heated.

Optimal soil

The seeds are sown in poor potting soil. The young plants, on the other hand, must be planted in a soil that has the following properties:

• nutritious
  
• relaxed
  
• permeable to water
  
• with a pH of 6.5 to 7

Add nutrients to the soil by adding a good serving of ripe compost or other slow release organic fertilizer before planting. An unsuitable pH value can either be increased by adding lime or lowering it with sulfur, depending on the value.

Tip: If you want it to be quick and practical, use special tomato soil. It is tailored to the needs of this nightshade plant.

Instructions for planting

1. Loosen the soil deeply and remove any weeds.
   
2. Then dig out planting holes that are about 5 cm deeper than the ball of the pot. Keep a minimum distance of about 80 cm between two rows. The minimum distance between two plants in a row should be about 60 cm.
   
3. First immerse plants with dry soil in buckets of water until the soil is soaked.
   
4. Snap off the cotyledons to prevent disease.
   
5. Carefully remove the ball of earth from the pot.
   
6. Place the tomato plant in the planting hole. In the tomato house with an open front, orient the flower stem inwards.
   
7. Fill the planting hole with soil, which you then carefully press down.
   
8. Thoroughly water the soil.
   
9. Use a climbing aid right away so that the tomato can grow upright on it and later find a good hold. Long spiral rods made of metal are ideal as a climbing aid. Tomato plants can also be tied to the greenhouse ceiling with strings.

Fertilize

The tomato is one of the so-called strong eaters. With the good starting supply during the planting period, it will only be there for a short time. That is why Solanum lycopersicum must be fertilized regularly with ripe compost during the entire vegetation period. Only sparingly until flowering, then every two weeks. The following organic fertilizers are ideally suited as supplementary nutrient suppliers:

• Horn shavings
  
• Nettle manure
  
• Comfrey manure
  
• Rock flour
  
• Mulch

If a mineral fertilizer is used, the focus should be on phosphorus, potassium, magnesium and sulfur as well as trace elements boron, iron and manganese. Nitrogen is also essential for tomatoes. However, only a low-nitrogen fertilizer should be used in the greenhouse.

to water

The soil must never dry out completely. Likewise, the earth must not be completely wet, and certainly not long-term waterlogging. When watering, the water must not wet the leaves. The pouring rules at a glance:

• Use rainwater or stale tap water
• water at regular intervals
• needs-based and heat-dependent
• early morning is ideal
• water in the evenings in summer
• check soil moisture beforehand
• it is better to water more often than with large amounts of water
• Put water directly on the roots
• Use a watering can, do not use a hard jet of water from a hose

Pricking out / cutting

Tomatoes like to proliferate, but space in the greenhouse is limited. But the risk of brown rot can also be minimized with courageous cutting. That Skinning the tomatoes directs the energy away from the leaf mass and into the fruiting process. About 4-5 fruit-bearing shoots should remain on each tomato plant.

• Completely free the lower 40 cm of the plant from leaves
• start pruning one week after planting out
• Repeat every two weeks until harvest
• remove all stinging shoots from the leaf axils
• snap it off with your fingers
• do not use scissors, do not tear out
• only cut off larger shoots carefully
• Shorten main shoots after the fifth inflorescence (load limit)

Tip: From August onwards, new flowers have little chance of turning into red tomatoes. Remove these consistently in order to direct the energy into already set fruits.

Important care advice: pollination

With tomatoes, insects and wind ensure that pollination goes smoothly. In a closed greenhouse, apart from the ventilation window, both are rarely or not at all. That's why the gardener has to help. Here are a few alternatives:

• Shake the inflorescence every two days
  
• briefly touch the inside of the flower with an electric toothbrush
  
• Brush over pollen sacs and stigma with a soft brush
  
• Simulate wind with a fan

In order for this care instruction to actually lead to “harvestable” success, the air temperature and humidity in the greenhouse of the tomatoes must be right. Make sure that the temperature does not exceed 30 ° C and that the humidity is between 50 and 80%. Otherwise the pollen can stick together. On the other hand, air that is too cool reduces the pollen's ability to germinate.

Pests and diseases

Tomato plants are not just a gardener's favorite. They are also on the menu of some pests, such as aphids and white flies. The high humidity in the greenhouse is particularly beneficial for spider mites and tomato leaf miners. In the closed space there is also more to be seen Tomato diseases:

• Bacterial wilt
  
• Velvet spot disease
  
• Gray mold

Keep an eye on your tomato plants. Act as soon as spots or evidence appear on leaves or fruits or parts of the plant peel off. Or if you discover pests.

frequently asked Questions