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Why is My Tomato Plant Turning Yellow?

You’ve done the research, found the perfect spot, prepared the soil, and finally started growing your tomato plants. Everything has been done right… but everything isn’t going right. When you see a yellow leaf on a plant that should be perfect, you can’t help but think “Why is my tomato plant turning yellow?!”

Good news—there is probably a simple solution.

Why is my tomato plant turning yellow?

Better news—we’ve compiled seven of the most common reasons to your tomato plant has turned yellow and we’ve got the possible solutions.

Read on to find out the answer to the question: “Why is my tomato plant turning yellow?”

Why is My Tomato Plant Turning Yellow?

Yellow tomato plants

Easiest Answers— Seed Leaves or End of Season

If your tomato seedling seemed to be thriving but then you found yourself wondering, “Why is my tomato plant turning yellow?” odds are good that it’s natural and inevitable.

The same can be said at the end of a healthy growing season. At the very beginning and the very end of a tomato plant’s life, there will be yellow leaves.

Symptoms

About three weeks after your seedlings sprout out of the ground, by the time they have 2-3 sets of true leaves, the first leaves will begin to turn yellow and fall off.

Similarly, since tomato plants are perennials, they grow and die in one season. At the end of the season, when temperatures start dropping, your entire tomato plant will start turning yellow.

Solutions

There’s nothing you need to do! The yellowing in these scenarios is natural and not harmful to your plant or the soil. 

If you want to hurry the first leaves along in falling off, you can go ahead and pinch them off.

And at the end of the season, go ahead and pull the whole plant up by the roots. If there’s still unripened fruit, you can hang them upside down inside until the fruit’s ripened.

Disease

Tomato plant disease

Tomato plants are living things, and living things get diseases. Sometimes, the answer to why is my tomato plant turning yellow is that it’s sick and needs some help recovering. Tomato diseases aren’t anything to mess around with. If you think one of your plants is infected, you need to take quick action to make sure it doesn’t spread to the rest of your plants.

Symptoms

Fungal and bacterial diseases can present in different ways, but there are many that will start with leaves yellowing. If the questions following, “Why is my tomato plant turning yellow?” include questions about dark spots on the leaves and stems, or soft, sunken spots on your fruits, you’re probably fighting a disease. 

Solutions

The solution to the disease is going to depend on which disease is infecting your tomato plant. Simple solutions include removing the affected branches, ensuring you’re only watering the base of the plant, and treating the plants with fungicide.

To find learn more about specific tomato plant diseases and how to treat them check out this post on The 7 Most Common Tomato Plant Diseases.

Nutrient Deficient

Yellowing Tomato Plant

Just like human bodies need the right vitamins and minerals in our diet to thrive, tomato plants are the same way. The answer to the question, “Why are my tomato plants turning yellow?” may lie in a nutrient deficiency.

Symptoms

The most common nutrients out of whack when your tomato leaves are turning yellow will usually be either nitrogen or magnesium.

If nitrogen is the answer to why is my tomato plant turning yellow, older leaves will begin turning yellow first. You’ll also notice you plant is growing slowly and looks lean and lanky instead of full and thriving.

If it’s magnesium your plant is lacking, your tomato leaves will become covered with blotches of yellow. They’ll turn from green, to spotty yellow, and eventually die.

Solutions

The quickest way to get nitrogen levels where they need to be is to use a fertilizer that’s rich in nitrogen. If you need help choosing one, go read The Ultimate Tomato Fertilizer Guide for some help!

If your tomato plant leaves are a blotchy yellow, the answer to a magnesium deficiency is exactly what it would be for humans—epsom salt! Simply sprinkle some directly onto the soil at the base of your plants or mix a teaspoon of epsom salt into a gallon of water and water as usual once a month during the entire growing season.

Pests

Pests on a tomato plant

The good news is, pests are one of the most obvious answers to the question why is my tomato plant turning yellow? If you see your leaves covered with little bugs, you know what’s going on!

Symptoms

If you notice your leaves are turning yellow and have small holes in them, take a closer look. Check on the underside of the leaves, as that’s where most critters, like aphids, like to spend their time. 

Also, look closely for a thin webbing. Spider mites will drain leaves of nutrients, leaving them yellow, but they’ll also leave behind their webs as a calling card.

Solutions

It may seem counterintuitive, but fighting bugs with bugs is actually a great way to fight pests making you question “why are my tomato plants turning yellow?”! 

Ladybugs are a great solution for many typical garden pests. They’re natural predators that will help keep your garden healthy without adding chemicals.

If ladybugs won’t do the trick, as they won’t for spider mites, insecticidal soap will help you fight the pests.

In either case, remove the affected yellow leaves before treating. They can’t be saved and there’s no point in your plant continuing to put effort into keeping them alive.

If you think you’re facing pests, but not sure which ones, check out the 15 Most Common Tomato Pests to figure it out.

Soil Problem

Soil

Your soil can be full of all the nutrients it needs, but if it’s overpacked and without adequate drainage or the wrong pH levels, your tomato plants will suffer and you’ll be wondering “Why is my tomato plant turning yellow?”.

Symptoms

The visible symptoms that will make you ask “Why are my tomato plants turning yellow?” are similar to those of nutrient deficiencies, like splotchy yellow leaves and stunted growth. That’s because a lot of times, soil that is too tightly compacted leads to weak root systems that don’t allow the plants to absorb the nutrients needed.

Solutions

Start by checking on the pH levels. Tomatoes do best in soil with a pH level between 6.5-7.0. If it’s off, correct it by adding organic compost to lower it or some lime to raise it.

If the pH levels are ok, loosen up the soil around your plants with a hand tiller and mix in organic compost. The natural organisms inside it will work through the soil to aerate and loosen it.

To avoid this from happening in the first place, add compost and manure to create a loose, rich environment in which your tomato plants will thrive.

Sunlight

Tomato garden

Tomato plants absolutely love sun! They need at least 6-8 hours of full sunlight a day in order to thrive. If they don’t get enough, you’ll certainly ask “Why is my tomato plant turning yellow?”.

Symptoms

Tomato plants that aren’t getting enough sun will begin to turn yellow, usually beginning from the bottom, where leave naturally get less light.

Solutions

This is a problem that’s usually best solved before it becomes a problem by ensuring that you’re planting your tomato plants in the sunniest part of your garden.

If you’ve already done the planting and you’ve narrowed the reason your plant is turning yellow down to a sunlight issue, you can try to help the plant along by removing the bottom leaves that are beginning to turn yellow. 

Thankfully, most tomato plants are hardy enough to lose some of the bottom leaves and still go on to produce healthy fruit. Just remember to try a new spot in the garden next year!

Transplanting

If you’re wondering why is my tomato plant turning yellow right after you’ve planted your seedlings, chances are good that they’re experiencing transplant shock.

Symptoms

If your newly tomato seedlings that are freshly planted directly in the ground suddenly start turning a pale yellow, never fear! This is normal and there’s hope.

Solutions

Most tomato seedlings experiencing transplant shock just need a little extra TLC and time to recover. Make sure the roots have plenty of water, but never enough that there’s standing water.

You can also help them with the transition by adding a little shade to them for a week or so. It just helps protect them from too much sun during a delicate transition period.

Watering Problem

Watering garden

Whether you’re overly attentive or very forgetful, watering problems can leave you questioning, “Why is my tomato plant turning yellow?”

Symptoms

Overwatered tomato plants will look dull and the leaves will start turning yellow with a brown outer edge.

Underwatered tomato plants will slowly turn yellow, then the entire plant will look droopy.

Solutions

Thankfully, this is an easy problem to resolve. If you’ve been overwatering your tomatoes, start spacing out the waterings. Before watering, insert your finger an inch or two into the soil at the base of your plant. If it’s still moist, wait another day to water.

If you’ve been under-watering your plants, start watering them more regularly. If you don’t have time, or have a hard time remembering, there are ways to make one watering last a few days!

So…Why is My Tomato Plant Turning Yellow?

Now that you have seven of the most common answers to the question “Why is my tomato plant turning yellow,” hopefully you can get to the bottom of it so you can keep enjoying fresh, bright, juicy tomatoes fresh from your garden!

For almost everything else you could want to know about growing tomatoes, check out our Tomato Page!