15 Ways to Fix Yellow Tomato Leaves and What Causes Them

For the avid vegetable gardener, there’s nothing more beautiful than gorgeous tomato plants growing in the backyard plot.

Nothing ruins that quite like yellowing, curling leaves.

If you’ve ever faced this problem, there’s a good chance that you’ve felt beside yourself as a result. Yellow leaves! What? Tomato plants are supposed to be green!

Fortunately, although there are countless reasons why tomato plants might develop yellow leaves, it’s easy to fix yellow tomato leaves. It all comes down to knowing what causes them and taking steps to prevent it from happening again.

What Causes Yellow Tomato Leaves?

tomato plant with dying leaves

There are several reasons behind your yellowing tomato leaves. To help heal your plants, you’ll need to first figure out what’s causing your plants to turn yellow in the first place.

One common issue is a fungal disease. Fungal diseases can cause yellow leaves on all kinds of plants but are particularly common on tomatoes. Both early blight and late blight produce yellow coloring on leaves, with early blight causing small spots that eventually grow large and late blight beginning on the upper leaves.

Fusarium wilt is another common fungal disease. This issue appears during times of warm weather and causes leaves to yellow usually on just one side of the plant. It typically begins with older, lower leaves. It can cause stunted growth and a failure to produce fruit.

Several viral diseases can cause yellow tomato leaves, too. These include single streak virus, tobacco mosaic virus, tomato yellow leaf curl, and cucumber mosaic viruses. In addition to yellowed leaves, you’ll also notice signs like malformations, brown streaks, curling, and stunted growth.

Of course, watering problems, pests, and nutritional deficiencies can cause yellow leaves, too. Some of the most common tomato plant pests include flea beetles, cutworms, hornworms, whiteflies, thrips, and aphids.

15 Ways to Fix Yellow Tomato Leaves

Now that you know why those pesky yellow leaves appeared in your garden, it’s time to start fixing the problem.  There are tons of great garden hacks to use this year to make sure your garden thrives!  Start with these tips for preparing seedlings indoors and end with an amazing garden harvest!

1. Use a Fungicide

spraying fungicide to diseased tomato plant
While a fungicide won’t be effective if a virus or nutrient deficiency is causing issues for your tomato plants, it will be for plants that are struggling from fungal diseases like a blight or fusarium wilt. Use a fungicide containing chlorothalonil for best results, but make sure you check the withdrawal time listed on the product so that you don’t accidentally find yourself eating chemically-treated produce.

2. Prune for Circulation

cutting or pruning of tomato leaves
Tomato leaves often turn yellow because they are suffering from fungal problems, as mentioned above. The spread of these diseases can often be halted in its tracks with a bit of proper pruning. Pruning will open up the air between the plants and allow for better circulation. Of course, spacing your plants out when you first put them in the ground can help prevent this issue, too.

3. Watch the Watering

watering tomato plant
You may not be able to totally reverse the yellowing leaves of your tomato plants by changing your watering habits, but you can improve the situation for sure. Water thoroughly and evenly, doing so from the bottom up rather than overhead. Consider installing drip irrigation systems or other “bottoms-up” watering systems so that water isn’t splashing fungal spores onto your tomato plants.

Both too much and too little water can wreak havoc on the leaves of your tomato plants. Water them carefully at the base and keep the leaves as dry as possible. Water deeply every five to seven days, depending on the weather and soil type, but let it dry out a bit between waterings.

4. Get Pest Problems Under Control

spraying tomato plant to get rid of pests by using insecticidal soap
Many viral diseases are spread by insects. Some of the biggest culprits include aphids, thrips, and whitefly. Do your best to get rid of these pests (following good watering and weeding practices, as well as growing companion plants and practicing crop rotation can help). You can control these pests by using insecticidal soap or horticultural oil. Some pests, like cutworms and hornworms, are easy to control by pulling them off the plant by hand.

If you prefer going in the natural direction, then make sure to check out these natural insecticides that are ideal for gardening. 

5. Discard Affected Plants

discarding affected tomato plant, showing roots, dry leaves and yellow fruits
In severe situations, you may have to give up and toss the entire tomato plant. This may be necessary when a viral disease has totally taken over your tomato garden. Throw out the plant and consider planting new, disease-resistant varieties instead.

6. Use BT

sparying BT on plants to get rid of pests
If you are still struggling with pests on your tomato plants and think they might be the cause of your yellow leaves, consider using Bt. Bt, or bacillus thuringiensis, is a natural soil bacteria that can help get rid of large tomato pests like hornworms and cutworms.

7. Add Fertilizer

adding fertilizer with a shovel on tomato plant
A couple of yellow leaves here and there on your tomato plants are usually nothing to worry about, particularly if they are found at the very bottom of the plant. In most cases, this simply means that the lower leaves aren’t getting quite enough sunlight or nutrients. You’ll notice lower leaves yellowing more often when the plant is fruiting, in fact.

However, sometimes yellow leaves are caused by an overall lack of nutrients in the soil, particularly if you notice that the yellowing is widespread. Nitrogen deficiency is the most common issue, so adding some nitrogen-rich fertilizer can help.

That said, it’s important that you conduct a soil test to make sure this is your issue. Some nutrient deficiencies present in odd ways, so you could find yourself fertilizing when it’s not really necessary. Even worse, an excess of some nutrients can cause yellow leaves too – so adding fertilizer might just be adding fuel to the fire.

Whatever the case may be, fertilizer at planting time and them monthly. Tomatoes like to be fed often, but be wary of overfeeding with nitrogen. This will take care of your yellow leaf problem for sure, but it will create lots of foliage at the expense of fruits.

Hint:  Check out these organic DIY garden fertilizers.  Tons of good ideas that are sure to add to your arsenal. 

8. Check with the Professionals

a professional gardener in white coat or lab coat checking the tomato plants
If you can’t figure out what’s causing your tomato leaves to be yellow, you may want to check with the experts in your area. Snip off a piece of the plant that is yellowing and bring it to your local gardening center or cooperative office. They should be able to give you an idea of what’s going on.

9. Move the Plant Into More Sunlight

tomato plant in the sunlight
If you’re growing your tomato plant in a container, this is an easy fix to make. Yellow leaves are often caused by a lack of sunlight, so if you can move the container into a spot where it will receive more sun, do it.

10. Loosen the Soil

panting a grown tomato
Compacted soil is another common culprit when it comes to yellow tomato plant leaves. Ideally, you should aerate the soil before planting time. However, if you find that this is not an option, you can dig up a bit of soil around the base of the plant, being careful not to touch the roots of your tomatoes.

11. Trim the Roots

dug tomato plant showing its roots and soil held by man
This is not something that should be done for just any case of tomato leaf yellowing. However, if you suspect root rot is to blame for your yellow leaves, a bit of root trimming just might save a plant in a last-ditch effort.

Root rot is usually caused by overwatering. It’s a fungal disease but the right conditions need to be present in order for it to manifest itself. To remedy this issue, dig up the plant with the root intact. Wash them under cool running water. Use a pair of sanitized shears to remove any mushy black portions of the roots. Replant the tomato plant, ideally in fresh soil.

12. Mulch

mulch in a tomato plant
A thick layer of mulch will not only help regulate soil moisture and soil temperatures, but it can also stop water from splashing back up on the plants from the ground. With all of these benefits, it’s a sensible step to take when you’re trying to stop tomato leaves from yellowing.

Start with this ultimate guide to mulching to learn more about the best types of mulch to use in your particular garden. 

13. Stake or Cage Your Plants

stak or cage the tomato plant
Plants that have foliage touching the ground are far more susceptible to fungal and viral diseases. Get them up and off the ground to prevent and treat this common tomato plant issue.

You can have fun making your own when you check out this list of DIY garden cages! So many fun ideas that are functional and pretty at the same time. 

14. Add Calcium

Epsom salts in a wooden cup
A common nutrient deficiency suffered by tomato plants is blossom end rot. If you add a bit of Epsom salts or powdered milk, you should find that the calcium and magnesium deficiencies suffered by your plants are taken care of – and so, too, are the yellowed leaves.

15. Do Nothing at All

green leaves of tomato plant in a pot
In some cases, the best remedy for yellow tomato leaves might be to do nothing at all! Some tomato plants produce yellow leaves, usually at the bottom, simply because the lower leaves aren’t getting enough sunlight. Therefore, you don’t need to do anything to get rid of the yellow leaves. If you’ve ruled out all of the other potential culprits and still have yellow leaves (but the rest of your plant is thriving), it might be time to stop obsessing and let it go.

Stop Leaves From Turning Yellow – For Good!

healthy green leaves of a tomato plant
Although there are several possible reasons why tomato plant leaves might turn yellow, this is a problem that is, fortunately, quite easy to fix. Sometimes it might require a bit of trial and error, but with practice, you can turn yellow tomato leaves from a cause of panic into something that rarely inspires worry.

Follow these tips, and you’ll be well on your way to a healthy, productive harvest of tomatoes.

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