- Suitable greenhouse
- planting time
- Optimal soil
- Instructions for planting
- Fertilize
- pour
- pinching/cutting
- Important Care Instructions: Pollination
- pests and diseases
- frequently asked Questions
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Unfortunately, there is no guarantee of a good harvest for tomatoes (Solanum lycopersicum) outdoors. In the greenhouse, the heat is right and the rain is denied access, so the tomatoes feel good. With the right care, cultivation is a sure-fire success.
In a nutshell
- Planting possible from the end of April/mid-May
- Observe the minimum distance and attach a climbing aid
- fertilize with compost or other organic fertilizers, keep soil moist
- pinch regularly and remove leaves
- pollinate by hand
Suitable greenhouse
Every tomato plant is happy about a large greenhouse made of glass. However, it is not a must for the covered cultivation. Tomato houses made of foil are also commercially available. Their lifespan is shorter, but they are comparatively very cheap. Smaller ones are even suitable for growing tomatoes on the balcony. You can also build your own construction at low cost. 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 planted only in mid-May. This planting time also applies to greenhouses that are not closed on all sides. Because even low sub-zero temperatures can kill 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 grow them at home from around mid-February. Either in the house on a warm and bright windowsill or in the greenhouse if it can be heated.
Optimal soil
The seeds are sown in poor potting soil. The planting of the young plants, on the other hand, must take place in a soil that is composed as follows:
- nutritious
- relaxed
- water permeable
- with a pH of 6.5 to 7
Add nutrients to the soil by incorporating a good dose of mature compost or other slow-release organic fertilizer before planting. Depending on the value, an unsuitable pH value can either be increased with lime or reduced with sulphur.
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
- Loosen the soil deeply and remove any weeds.
- Then dig planting holes about 5 cm deeper than the root ball. 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.
- First immerse plants with dry soil balls in buckets of water until the soil is soaked.
- Pinch off the cotyledons to prevent disease.
- Carefully remove the soil ball from the pot.
- Place the tomato plant in the planting hole. In the open-fronted tomato house, direct the flower stalk inward.
- Fill the planting hole with soil, which you then press down carefully.
- Water the soil thoroughly.
- Use a climbing aid right away so that the tomato can grow upright and later find a good hold. Long metal spiral rods are ideal as climbing aids. Tomato plants can also be tied to the greenhouse ceiling with strings.
Fertilize
The tomato is one of the so-called heavy feeders. With the good starting supply during the planting season, it only lasts for a short time. For this reason, Solanum lycopersicum must be fertilized regularly with mature compost throughout the growing season. Only sparingly until flowering, then every two weeks. The following organic fertilizers are ideal 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. In the greenhouse, however, only a low-nitrogen fertilizer should be used.
pour
The soil must never dry out completely. In the same way, the earth must not be completely wet, let alone long-lasting waterlogging. When watering, the water must not wet the leaves. The watering rules at a glance:
- Use rainwater or stagnant tap water
- water at regular intervals
- needs-based and heat-dependent
- early morning is ideal
- additionally water in the evening in summer
- check soil moisture beforehand
- better water more often than with large amounts of water
- Put water directly on the roots
- Use a watering can, not a hard jet of water from a hose
pinching/cutting
Tomatoes like to grow, but space in the greenhouse is limited. But the risk of brown rot can also be minimized with courageous cutting. Pinching the tomatoes directs energy away from the leaf mass and into fruiting. About 4-5 fruiting shoots should remain on each tomato plant.
- Completely remove leaves from the lower 40 cm of the plant
- start pinching out a week after planting out
- Repeat every two weeks until harvest
- remove all stinging shoots from the leaf axils
- pinch off with your fingers
- do not use scissors, do not tear out
- Only carefully cut off larger shoots
- Shorten the main shoots after the fifth inflorescence (load limitation)
Tip: From August, new flowers have little chance of turning into red tomatoes. Remove these consistently to direct the energy to fruit that has already been set.
Important Care Instructions: Pollination
In the case of tomatoes, insects and wind ensure that pollination runs smoothly. In a closed greenhouse, apart from the ventilation window, both of these hardly occur or not at all. That's why the gardener has to help. Here are a few alternatives:
- shake the inflorescence every two days
- Touch the inside of the flower briefly 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 for the tomatoes must be right. Make sure the temperature does not exceed 30°C and the humidity is between 50 and 80%. Otherwise the pollen can stick together. Air that is too cool, on the other hand, reduces the ability of the pollen to germinate.
pests and diseases
Tomato plants aren't just a gardener's favourite. They are also on the menu of some pests, such as aphids and whiteflies. However, the high humidity in the greenhouse favors spider mites and tomato leaf miners in particular. More tomato diseases also show up in the closed space:
- bacterial wilt
- velvet spot disease
- gray mold
Gray mold on tomato plant
Keep an eye on your tomato plants. Act as soon as spots or coverings appear on the leaves or fruit, or parts of the plant sprout. Or if you discover vermin.
frequently asked Questions
How can I attract bees inside the greenhouse?Bees and other pollinating insects have a sensitive olfactory organ. If space in the greenhouse allows, plant a few aromatic plants in it. Chances are that their scent attracts bees. However, you must open a window or the greenhouse door for them.
Can I prevent tomato diseases in the greenhouse?Most diseases are favored by planting too close together. It is understandable to want to increase the yield by planting many plants, but it is important to keep the recommended minimum distance when planting in the greenhouse.
Are optical changes in the tomato always a symptom of disease?Pests and diseases are not always responsible for unsightly changes in leaves and fruits. A maintenance error can also be considered as a cause. Uneven water supply causes the fruit to burst, too much sun causes sunburn. Blossom end rot usually indicates a lack of calcium, green collars to a lack of potassium and too much nitrogen fertilization.
Can tomatoes be overwintered in a greenhouse?Yes, but with restrictions. The tomato house must be heated to 22-24 °C in winter. In addition, not every variety is suitable for overwintering. It works best with wild tomatoes or cherry tomatoes.