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2 Major Reasons Your Tomato Leaves Are Yellow

Now that summer is here, it's time to eat bright red tomatoes, sweet from their hours in the sun. Sometimes tomatoes don't turn out the way you want or maybe you never even get to see tomatoes grow on your precious plant. Like many other garden fruits and vegetables, tomatoes are susceptible to their own set of problems, including yellow leaves.

The reason your tomato leaves are yellow could be attributed to many different causes. Depending on the cause, you should be able to bring your tomato plant back to health and still enjoy those delicious tomatoes!


watering seedling tomato

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Overwatering and underwatering your tomato plant can cause yellow leaves. Gardeners and growers will want to pay careful attention to the soil around a tomato plant, making sure it's not too dry or too wet. While it's easy to think that surely a plant can't have too much water, tomatoes are very delicate. Overwatering is a major cause of yellowing leaves and excess water can harm the plant's roots, effectively drowning them.

If you think you are overwatering, stop watering your tomatoes for a day or two and continuously check your soil. Once the top couple of inches are dry, you can start watering your plant again. With too much water, roots can begin to rot. If your tomato plant's roots are rotting, it will be very difficult to save the plant. Growers can try carefully pulling the plant off and using garden shears to cut off the rotted roots. You may then be able to replant the tomatoes.


Hot conditions and not enough water could also cause yellowing leaves. Without enough water, the plant can't properly hydrate so leaves die. Continuously check the moisture of your tomato plant's soil. If the top couple of inches of soil is very dry, it's time to water with a watering can. You may also consider watering plants in the morning to hydrate them for the day and prevent any evaporation caused by the sun.

Garden Insects

Close up view of person using homemade insecticidal insect spray in home garden to protect roses from insects.

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It's well known that having an outdoor garden means dealing with the plentiful insect life that wants to use your plants for their own food. While we want to do our best to preserve the life of all things, sometimes action needs to be taken.

These pests could be the reason your tomato leaves are yellow. When these insects feed on the plant, they often reduce the plant's capacity to turn sunlight into energy, both by decreasing the number of leaves on the plant and blocking the plant from the sun.

Tomato hornworms and aphids are two major tomato pests, but both of these insects can be removed (or killed) from your plants to ensure the growth of healthy tomatoes. If the tips below do not help and you still find yourself battling bugs, you may consider moving your tomato plants to a pot or tall garden box. Getting plants out of the ground can sometimes help with pest issues.

Hornworms are best removed by hand while aphids can be a bit more difficult to tackle. When picking up the caterpillars by hand, be sure to use gardening gloves or some other tool to prevent contact with your skin. For aphids, creating a spray with castile soap is an incredibly easy and effective way to kill these insects.

Using the soap spray is safe for your plant and beneficial insects. Additionally, you won't have to worry about ingesting any insecticides when popping that delicious tomato in your mouth!

READ MORE: 9 Plants to Plant Next to Your Tomatoes for a Bountiful Garden