Finding yellow leaves on plants is very common. The scientific term for the phenomenon is chlorosis. For mature plants, it may simply mean you are at the end of the growing season. For tomato seedlings, yellow leaves mean something is wrong – but don’t panic just yet.
From nutrient deficiencies to improper watering, many of the factors that lead to yellowing tomato seedlings are easy to reverse. This is one of the most common tomato seedling problems and once you determine the cause, you can fix the problem.
I will share the main reasons why tomato seedlings turn yellow and how to fix them. Just avoid the following care mistakes that cause this problem. Then start working towards a solution so you can grow strong, healthy, green plants that produce tons of delicious tomatoes.
Why are my tomato seedlings turning yellow?
Yellowing is very common among the possible problems when tomato cultivation and it’s often repairable, so no need to stress. The list of care mistakes below will help you determine the cause of yellowing tomato seedlings and provide solutions to help the plants regain their green color.
1. You are overwatering
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Overwatering seedlings are probably the most common underlying cause of yellowing leaves. It can be difficult to get the right balance with water. Seedlings need constant moisture, but too much water can cause suffocation and eventual root rot. This results in tomato seedlings turning yellow because they cannot absorb sufficient nutrients.
When watering seedlingsaim for soil that never dries out completely, but is never soggy or waterlogged. Your seedlings should be in trays or small pots with light, well-draining soil potting mix like this one from Miracle-Gro and drainage holes so that water cannot be trapped.
If your seed trays are waterlogged and the seedlings are turning yellow, let them dry out a bit before watering again. If the container does not drain, repot your seedlings in a container that will drain the excess water.
2. You’re Underwater
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Tomato seedlings may also turn yellow if the watering balance is tipped in the opposite direction to too dry. As with overwatering, submarine it prevents the roots from getting enough nutrients to promote healthy, green growth.
If you catch this problem early, it is very easy to fix. Aim to water the seed trays regularly, keeping the soil consistently moist but not soggy or wet. When dryness is a problem, it is important to check the seedlings daily. If you see dry soil on top, give them some water.
A watering can that can direct water to the roots and produces a fine spray, such as this watering can from Amazonit is good for sensitive young tomato plants.
3. You don’t fertilize
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Watering problems are common and easy to fix, but if you’ve mastered it and still have yellowing, it’s time to look at nutrient deficiencies. The deficiency most likely to cause yellow leaves is nitrogen.
Look how it the leaves have turned yellow. If the lower leaves start to turn yellow, followed by the upper leaves, then nitrogen is the likely culprit. Less commonly, iron or potassium deficiency can cause yellowing of younger leaves.
To prevent nutrient deficiencies, you can use compost in the potting mix when starting the seeds. This will provide them with a rich substrate to promote healthy growth.
Alternatively, you can fertilize the seedlings with a balanced but diluted liquid fertilizer after the first true leaves emerge. This organic liquid fertilizer from Amazon is a good choice. Apply the diluted solution every two to three weeks as the seedlings grow.
4. You don’t provide enough light
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Bright light is essential for healthy seedling growth. Are your tomato plants getting enough light? If not, they can definitely turn yellow from reduced photosynthesis.
Another sign of insufficient light is foot development. This means the stems become tall but thin as they stretch to reach any available light.
Make sure your seedlings get 12 to 16 hours of direct, bright light per day. If sunny windows are rare, use artificial lights, such as this affordable plant light from Amazonto give the tomatoes a boost.
Place the lights a few inches from the tops of the saplings. If using light from a window, rotate the seed trays regularly so they receive even sunlight.
5. Your plants have a disease
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Hopefully you have found the cause of your seedlings turning yellow in one of the above issues. Tomato diseases they are much more serious and more difficult to manage. It is also less likely to be the problem compared to typical light, water and nutrient issues.
Fungal infections are more common, but you may also have a bacterial problem. Less common are viral diseases in tomato seedlings. Diseases in tomato seedlings often start with yellowing from the top of the plant down. They are also associated with other signs such as leaf spots or wilting.
If you see signs of a fungal disease, such as Fusarium wilt or early blightremove affected leaves or entire seedlings. You can try a fungicide, such as that of Bonideif the infection has not spread too far.
Bacterial diseases such as bacterial leaf spotthey often come from the seed. That’s why it’s so important to buy from trusted sources. Burpee has lots of high quality tomato seedsincluding many disease resistant varieties. If your seeds were infected, all your seedlings are likely to be affected and you may have to start over.
To prevent disease in tomato seedlings, start with good seeds. Use clean, sterile seed starting mix and seed trays. Avoid overcrowding your seedlings, which can lead to the spread of disease. Good air flow between plants is also important. Water only at soil level and remove any seedlings that look sick as soon as you spot signs of disease.
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For tomato seedlings, yellow leaves can mean many things. It’s a common occurrence and shouldn’t be too much of a concern, as long as you determine the cause. The most important thing you can do when growing tomatoes from seeds is to closely monitor the seedlings as they grow.
Check them at least once a day for signs of watering problems, nutrient deficiencies, disease and other problems. The earlier you catch these problems, the easier they are to correct and the more likely you are to save your little seedlings.
