10 Reasons for Tomato Plant Leaves Curling Up

Don’t stress if you find tomato plant leaves curling up; there are several reasons this might happen to your plant.

I took a walk in my garden last week and noticed that I had a few tomato leaves curling up. I knew immediately that this was more than likely caused by the extremely hot weather we were experiencing – and I might have forgotten to water when we went to the lake.

Oops.

While my tomato plant leaves gradually uncurled and went back to normal with more watering and cooler temperatures, I know that this isn’t always the case. Last year, we had tomato leaves curling up for a different reason – micronutrient deficiency.

If you notice that your tomato leaves are curling upwards, here are a few of the common causes.

Why Are My Tomato Plant Leaves Curling Up? 8 Reasons

When you see the tomato leaf curl, don’t panic. It’s like when you have a bit of a cold or a belly ache. While it could indicate a more serious problem, it’s usually not a big deal and easily remedied.

Make sure you check your garden frequently for signs of a problem. That allows you to take action faster and stop the problem before it kills your plants.

Let’s look at the reasons why your tomato plant leaves curl up.

1. Environmental Factors

Environmental issues are the most common reason you will notice tomato leaves curling up. That might mean your tomatoes are exposed to too much sun or face high temperatures.

Tomato leaves curling up also could be caused by too much wind, adding stress to your plants. If your plants aren’t properly staked and supported, the plants might twist, causing the leaves to curl and die back.

Think of tomato leaves as small solar panels that collect sunlight for the plant. If they receive ample sunlight, the plant forces the plant to curl and close up the leaves to prevent sunburn.

Temperatures are also a problem. If your location faces a heatwave, tomato leaves curl up as a protective measure against the excessive heat.

Don’t forget rain! We all love when it rains, and we don’t need to water that day. However, if you face several days of heavy rain in a row, the excess moisture is an environmental factor that plants dislike. Their roots suffer in standing water.

Don’t panic! If this is why your tomato leaves curl up, then as soon as the environmental problems change, you’ll notice the leaves opening and going back to normal. Another option is to install shade cloth over your plants to protect them from the afternoon sun.

2. Improper Watering Techniques

Another reason that your plants might have leaf curling is that you need to give your plants more water. Tomato plants need ample water; in general, tomato plants need one to two inches of water per week. Container-grown tomato plants need more water than that.

So, if it’s hot outside and you don’t provide enough water (a combination of environmental factors and lack of water), you might see your tomato leaves curling up.

It’s important to note that both under and overwatering will lead to stress and problems. If you fail to provide your plant with enough watering, the plant is unable to perform its essential functions. That’s why the leaves curl.

However, providing too much water is also a problem. Overwatering creates standing water near the tomato plant roots. Too much water prevents water from being transported up the roots to the plant cells, and the roots are unable to absorb any oxygen.

Overwatering typically leads to other symptoms before leaf curling, but it’s important to know that both cause issues.

3. Micronutrient Deficiency

If you notice your lower leaves curling up, the typical reason is that your soil has a micronutrient deficiency. However, most of the time, plants display this with yellowing tomato leaves before any curling happens.

You can fix a micronutrient deficiency in a few ways.

• Add fresh compost around your tomato plants.
• Use an all-purpose fertilizer around your plants to amend the soil and get your plants back on track.
• Consider using Azomite, which is a clay compound full of micronutrients.

Related: Did You Find Tomato Leaves Turning Yellow? Here are 10 Reasons!

4. Curly Top Virus

Take a close look at your tomato plants and see if they’re growing in a wiry pattern, with the smaller leaves at the top of the plant curling. This is a sign of a disease called the Curly Top Virus.

Curly top virus spreads by leafhopper pests and typically infects only one plant in your garden. That’s great news for you because it means that the virus doesn’t spread to other plants.

The bad news is that the curly top virus greatly affects the growth of the infected plant. You can let your plant reach maturity, but don’t leave the plant in the garden over the winter and remove it.

5. A Different Tomato Viral Infection

Curly top virus is only one tomato viral disease that leads to leaf curl. Diseases are something plants face, and other types will cause similar symptoms. Here are some other viral diseases your plant might face.

• Tomato Yellow Leaf Curl Virus: This viral disease causes the leaves to curl and turn yellow or pale green along the edges. The leaves curl upwards like a cup. Yellow Leaf Curl Virus spreads by whiteflies who carry the disease to your tomato plants in your garden.
  
• Tomato Mosaic Virus: This viral disease causes leaves to roll inwards and features other distinguishing symptoms, such as spotting coloring of the leaves and browning inside the fruits.

If you rule out the other potential causes of your tomato plant leaves curling, a viral infection could be the culprit. Unfortunately, diseases spread wildly, and keeping these in your garden can be dangerous. So, the best course of action is to remove the plant from your garden and destroy it.

6. Excess Nitrogen

If you add too much nitrogen to your soil, you might also notice leaf curling. After the leaves curl, they might become thicker and dark green. You’ll notice these symptoms most often on heavily pruned tomato plants.

At this point, don’t apply any more fertilizer to your plant and let the plant use up the nutrients in the soil. Make sure you test your soil next year before adding any more natural nitrogen sources to your garden.

Related: 11 Natural Nitrogen Sources All Gardeners Need to Know

Typically, excess nitrogen is an easy problem to fix; you wait. Over time, the plant heals as the plant uses nitrogen and nutrients leak out through the water. Applying the right fertilizer at the right time is best to avoid overfertilizing.

Related: How to Fertilize Tomato Plants for the BEST Harvest Ever!

7. Pruning Too Much

Pruning stresses out your tomato plant, but it’s essential for caring for it. The leaves on your plants are how they make food, converting sunlight into energy. So, if you remove too many leaves, then your plant will struggle.

Over-pruning, especially on a young or poorly established plant, will cause so much stress that it results in curling, yellowing leaves, stunted plant growth, and decrease fruit production. Also, it’s important to avoid pruning determinate tomato plants. You should only prune indeterminate tomatoes.

Tomato pruning tends to be a bit of a controversial topic since some gardeners state you should never prune. I’m not on the side of the controversy, but if you decide pruning works for your garden, always be cautious and pick to prune less, not more.

Related: How to Prune Tomato Plants: 7 Steps for Success

8. Herbicide Damage

Tomato plants are sensitive to chemical drifts, especially different herbicides. Herbicide drift happens when farms or gardeners near you spray weed control, and it’s carried by the wind, potentially landing in your garden.

When your tomato plants have herbicide damage, the leaves might curl upward or downwards, but they also look twisted and have malformed fruits that you shouldn’t eat. New growth typically shows the signs of herbicide damage first, and the leaves tend to twist around the stem.

Watch your plants. Sometimes, the new leaves and branches on the plant might recover; if they don’t, you should pull the entire plant out of the garden.

Thankfully, this reason for tomato plant leaves curling is not common. Unless you use weed killers in your garden or live near crops sprayed, you won’t face this issue. You are more likely to face a viral disease or environmental stress.

9. Pest Damage

If you notice that you have pests on your tomato plants, like tomato pinworms, you might end up with leaf curling. When the pests suck out sap from your tomato leaves, it causes the leaves to curl up and eventually wilt.

Another pest that causes tomato plant leaves curling is broad mites. Broad mites feed on young tomato leaves and flowers, injecting toxins that cause the leaves to twist and curl.

Identifying broad mites is difficult; you cannot see them with the naked eye. The only way to know that broad mites are your problem is their damage. A serious infestation may cause the underside of the leaves and fruits to turn bronze.

Treating this problem relies on you using the proper methods to eliminate the tomato plant pests in your garden. Those with a broad mite infestation should try a sulfur-based miticide but always read your tomato variety information first. Some cannot handle sulfur. Insecticidal soaps are another option to try.

However, plants with severe pest infestations should be removed before the problem gets worse.

10. Transplant Shock

Moving tomato plants from growing indoors to outside is a big deal, and it takes proper steps. You must go through a process called hardening off to avoid your plants dying after all the weeks inside.

When you plant tomato seedlings outside, it’s a big change for these little plants! This change leads to transplant shock, which happens when there is root damage during transplanting outside.

Tomato roots are delicate and dislike any sort of disturbance. It may cause wilting, yellowing leaves, and leaf curls. The good news is that mild transplant shock is no big deal; after a few weeks, your plant will look good as new.

What about Tomato Leaves Curling Down?

What happens if you walk in your garden and notice that your tomato leaves are curling down?

That means your tomato plants have something else happening. Tomato leaves curling down typically indicates that your plants lack nutrients due to root rot.

What is root rot?

Well, this happens when your tomato plants receive too much water either from you or too much rain, and it causes the roots to rot, preventing the plant from up taking more water. Root rot causes the plant’s roots to contract and close, and if the overwatering continues, the roots will shut down entirely, causing the plant to die.

So, what can you do to save your plants?

The best thing is to do stop watering your tomato plants. Wait for the plants to soak up as much as possible. It typically sorts itself out, and in the future, make sure you improve the drainage of your garden beds.

Watch Your Tomato Plants

Growing tomato plants can be tricky, especially if you don’t pay attention to your plants regularly. You never want to miss something like your tomato leaves curling up that could indicate a problem. Thankfully, tomato leaf curl rarely means that your tomato plants are going to die; you can still expect a harvest this summer!

Check out a few other tomato growing articles

• 12 Tomato Growing Hacks
• Why You Have Holes in Your Tomatoes
• The Difference Between Indeterminate and Determinate Tomatoes
• 7 Reasons Your Tomatoes Aren’t Ripening