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Tomatoes (Solanum lycopersicum) from your own garden taste particularly good. They don't need a lot of space and can even get along in a bucket on a balcony. Besides regular watering and weekly fertilization, there is not much to do, the tomato plants are easy to care for. Nevertheless, care errors, diseases or pests can occur, which cause yellow tomato leaves, for example. Depending on the cause, the problem can be solved with simple solutions or with a little effort.
Yellow Tomato Leaves
Yellow tomato leaves are particularly troubling when they are not a single spot or leaf, but when a large part of the plant is affected. In order to find out the cause and to be able to choose the right solutions, the plant must be examined carefully. The following questions should be answered:
- are only individual tomato leaves, tomato plants yellow or does it affect all of them?
- do the older leaves turn yellow or do the young ones?
- does the entire tomato plant turn yellow?
- are there any other abnormalities?
care mistakes
Although the cultivation of tomato plants is not very complicated, there can always be small mistakes that go unnoticed. However, unlike diseases or pests, they are easier to fix. Mistakes in care can be suspected above all when many or all plants are affected. As a rule, all tomato plants in the garden are cared for in the same way.
Possible are:
- wrong treatment of young plants
- too little light
- wrong fertilization
- too much or too little water
Treat young plants properly
Yellow tomato leaves after moving outdoors are particularly common if the tomato plants have not been sufficiently hardened off. When grown under glass or indoors, Solanum lycopersicum is not used to sunlight. If the young plants are placed outside without hardening, the change will lead to yellow leaves on the tomatoes.
More symptoms
- sagging leaves despite watering
- slow or absent growth
- burns on the leaves
remedy
In this specific case, you can only wait and try to provide the plants with the best possible care so that they can recover. The yellow coloring of the tomato leaves will then disappear over time. It can also happen that older leaves are shed. However, the new growth is then healthy.
The next young plants are then hardened by gradually acclimating them to the sunlight. To do this, take them outside during the day as soon as it is sufficiently warm. In the shade for the first few days, later also in the sun. At night or when it's too cold, the plants stay indoors.
Correct lighting conditions
Tomatoes are among the plants that are very light-hungry. They grow best in full sun, alternatively in partial shade. If the plants don't get enough light, the tomato leaves can turn yellow.
More symptoms
- Geiltriebe (long shoots without leaves)
- New growth remains weak
- hardly any flowers
remedy
The easiest way to do this is with plants that grow in tubs, they are simply placed in a place with more sunlight. Plants growing outdoors may need to be transplanted, or other ways of providing more light access. Strong midday sun should be avoided.
nutrient supply
Solanum lycopersicum is one of the heavy feeders, only with regular and high nutrient addition will healthy, strong plants develop that bring rich yields. Depending on which nutrient is missing, different symptoms can occur on the tomato:
- Lack of growth, yellow cotyledons, older leaves die off, fruits remain small: lack of nitrogen
- older tomato leaves turn yellow from the inside, leaf veins and edges remain green: magnesium deficiency
- yellow edges and tips on leaves, later brown, wilting, leaves and plants remaining small: potassium deficiency
- Entire plant turns yellow, flowers rot: lack of calcium (cause of blossom end rot)
- yellow leaves with green veins: iron deficiency (possibly too much lime in the soil)
- yellowed leaf tips, rolled up, dying leaves: copper deficiency
- the plant takes care of despite successful fertilization: lack of lime
remedy
Tomatoes grow best in very nutrient-rich soil. The ground should be prepared accordingly. Compost or manure can be introduced as early as autumn. Green manure is mown and dug up just before planting the tomatoes. When planting, horn shavings and rock flour are placed in the planting hole. This also applies to potted plants.
tip: If the bucket is large enough, a layer of manure can be placed as the bottom layer. This is followed by some soil so that the roots of the young plants do not burn.
If the soil is well supplied, it is sufficient to fertilize the tomatoes every two weeks. If they are mulched all the time, fertilization can be even less frequent. Container plants, on the other hand, are supplied with liquid fertilizer once a week or horn shavings are worked into the top layer of soil. Once a month, mix rock flour under the substrate to prevent a lack of lime.
tip: It can be worth having a soil sample from the garden tested for nutrient deficiencies.
Proper water supply
There can be both too much and too little moisture in tomatoes. The symptoms are similar:
- limp plants, leaves hanging down
- yellow tomato leaves, possibly brown if dry
- reduced new growth due to lack of nutrients
remedy
If the substrate is too dry, you should water more frequently and more thoroughly. A mulch layer also prevents too much water from evaporating. Sandy soil can store water better with the help of humus. It is more difficult if the plants are too wet. Waterlogging can cause the roots to rot. Potted plants are best repotted. You should remove the damaged roots. You should also ensure good water drainage in the new bucket. If tomatoes are cultivated outdoors, good drainage must be ensured when planting. If the location is still too wet, the outdoor tomatoes that are taking care of themselves are also transplanted. Loamy soil can be made more permeable with sand.
diseases and pests
If the tomato plants are well cared for and care mistakes can be ruled out, you have to consider diseases and pests. This also applies if only individual plants of the tomato have yellow leaves. The main causes are:
- leaf spot disease
- bacterial wilt
- thrips
- white flies
leaf spot disease
Tomatoes are susceptible to many fungal diseases. One of those responsible for yellowing foliage is leaf spot (Septoria lycopersici). Small, watery spots with a black edge form before the leaves turn yellow. The affected leaves eventually die off, weakening the plant. The fruits remain small but are edible. The disease cannot be treated in the home garden. However, you should remove infested leaves and dispose of them in the household waste.
Prevention (for all fungal diseases)
- Keep plants above ground dry
- Canopy protects against rain
- airy location and wide planting distances ensure sufficient air circulation
- Pinch plants regularly to prevent overgrowth
- take special care in hot and humid summers, check plants often
- use resistant or tolerant seeds
- air frequently for plants in the greenhouse
- remove the lower leaves on the stem
Tomatoes with a canopy
bacterial wilt
The bacterial weekle (Corynebacterium michiganense) is characterized by yellow tomato leaves. Cut open shoots show brown-yellow vessels. As the disease progresses, the leaves turn brown and fall off. The infection can also spread to the tomatoes, making them inedible. For prevention, you should follow the same instructions as for leaf spot disease.
Treatment of diseased plants:
- separate healthy from diseased plants
- remove and destroy affected leaves
- Remove mulch and loosen soil
- mix compacted soil with sand
- reduce fertilization
- Tonics generally ensure healthy growth
thrips
These tiny flies suck the sap from the leaves, turning them yellow. The larvae, however, attack the roots. Outdoors, thrips (Thysanoptera) usually do not become so common that treatment is necessary. In the greenhouse, they can do a lot of damage. However, fighting there is easier.
Treatment:
- spray outdoors with soft soap solution (mix 1 liter of water with 15 ml of soft or curd soap)
- alternatively, dust tomatoes with rock flour
- Beneficial insects (predatory mites, hoverflies) can be used in the greenhouse
- Glue boards are also helpful
white flies
The small whiteflies (Trialeurodes vaporariorum) damage many kinds of vegetables. In the greenhouse, however, they can become particularly troublesome. Like thrips, they suck the sap from plants. The leaves of the tomatoes will then turn yellow over time and the tomato will die. Outdoors, a vegetable protection net protects against whitefly infestation. If the tomatoes are in a tomato house, you can cover the entire construction with a net, but this must be very dense.
Treatment:
- in the greenhouse with glue boards or parasitic wasps
- Yellow boards can also help outdoors, shaking the plants from time to time so that the flies fly up and get stuck on the boards