Tomatoes: What Can Go Wrong?

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If you were to take a poll of the most popular vegetable grown in the garden, I’d be hard-pressed to think it was anything other than the tomato plant. It seems as though most gardeners (new and veteran) take pride in growing tomatoes in their gardens.

Just because tomatoes are popular, however, doesn’t make them easy to grow. Gardeners regularly encounter tomato plant problems.

So what all can go wrong with tomato plants, and how can you prevent or deal with those problems? On this episode of The Beginner’s Garden podcast, we explored the most common issues gardeners face when growing this juicy red fruit. You can take a listen here or continue reading.

15 things that can go wrong with tomatoes

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Tomato Leaf and Plant Problems

Early Blight and/or Leaf Spot

Early Blight presents itself as yellowing leaves toward the bottom of the plant. They may have a target spot with black in the center. Septoria Leaf Spot is similar in its showings except the spots are usually lots of smaller brown spots instead of one large one.

early blight tomato yellow spots on leaves

These are both fungal diseases that come on your tomato plants, usually after heavy rains and humid air which, of course, breeds fungus. I consider these two diseases to be a pain that I have to stay on top of each season in order to keep it from getting away from me. Typically, early blight shows up early in the season and septoria leaf spot appears later, though that isn’t always the case.

Once you notice one of these issues, clip these lower leaves, but only when it’s dry, to keep the fungus from traveling up the plant. And while there are many other diseases that could affect your plants, these two are the most common.

Stunted Growth in Tomato Plants

A lot of people notice stunted growth in tomato plants, and while it’s almost impossible to diagnose the reasoning from one garden to the next, I can say that there have been a few reasons for this in my garden.

Too Cold

If the daytime and nighttime temps are too cold or the soil is not warm enough, tomato plant growth could be much slower than you would like it to be. The good news is that as the weather warms up, the plants typically pick up their pace in growth.

Ripe tomato picked from the garden

Less than ideal soil

If your tomato leaves look healthy and you don’t see a visible issue, the next step is to consider your soil. I’ve worked for years to build up my soil into a better growing condition for all of my plants, but during those first few years, the clay content inhibited the drainage all plants need. Lack of drainage is just one symptom of poor soil, but there could be other reasons as well.

If you suspect soil that’s less than ideal, start amending your soil now and work on building it up for the future years. Start with a good layer of compost on top. If you want a quicker “fix,” consider planting those tomato plants in raised beds or use the straw bale gardening method. I use both of these options for tomato plants with consistently better results than my tomatoes in the ground.

new raised bed

Lack of Nitrogen

If you find that the upper leaves of the tomato plants are a healthy green color, but the lower leaves are more of a pale green or yellow, this could be a case of a lack of nitrogen. If you suspect this, try adding an organic nitrogen source such as fish emulsion to the soil. Just know that those lower leaves won’t turn green again, so it might be a better idea to go ahead and clip them. Just don’t remove more than 1/3 of the plant at any one pruning.

Root Knot Nematodes

If you notice wilting leaves and stunted growth, take a look at your plant’s roots. If you observe little knots along the roots, chances are you have root-knot nematodes. These are pretty tough to deal with. Your best defense here is to play offense for next season.

You can start by solarizing your soil, planting marigolds now in the space you plan to plant your tomatoes next season, and you can try and plant types that are more resistant to the nematodes. These aren’t quick fixes but they are important to put into place for the future.

Poisoned Plants

A few years back, I went out to the garden to find that my tomato plants just didn’t look right. Their leaves were curled in and twisted. After doing some research, and found out that my plants had been poisoned due to using hay mulch that had been sprayed with an herbicide.

hay poisoned tomato leaf curling

While the amount of herbicide that comes in contact with your plants is completely dependent on a number of factors, I strongly encourage you to avoid it at all costs and use other organic mulch options in the garden. I even go so far as to avoid horse manure where the animals have eaten the hay. It’s simply not worth the problems they can cause in the long term and short term.

But what if you haven’t used any tainted hay or manure and you still notice these curled and twisted leaves? There may be a chance that you live near a farm that sprays these herbicides, and your plants are affected due to the herbicide drift. If this is the case, try spraying your plants with water to get those chemicals off of the leaves.

Tomato Fruit Problems

Blossom End Rot

When the bottoms of your tomatoes look like they are rotting with a black rotten spot, you’ve got Blossom End Rot. This is more common earlier in the season and with determinate tomatoes. Typically, this is caused by the plant not taking up enough calcium, but, surprisingly, more calcium isn’t usually the answer.

More often than not, this is due to lack of water or inconsistent watering. If you will make sure that your plants are getting the water they need at a consistent rate, you can really tell a difference in the occurrence of Blossom End Rot.

blossom end rot on tomatoes

If you feel like you are watering well and consistently, I recommend a soil test to check not only your soil’s calcium level but also its pH. There is a chance your pH is off, which can also affect the plant’s ability to uptake calcium.

Beautiful Plants with No Fruit

Nutrient Imbalance

It’s getting late into July and August and your tomato plants are huge. They even have flowers popping up all over. There’s only one problem: there are no tomatoes. One possible cause is that your tomatoes are getting too much nitrogen and not enough of other nutrients like phosphorous.

I’ve seen this first hand with a tomato plant my mom once grew using potting soil with high nitrogen content. While the plant was big and beautiful, the fruit didn’t show up. If you find that this is your case, try and add a water-soluble fertilizer void of nitrogen, but full of potassium and phosphorous.

Too Hot and Too Humid

While imbalance can definitely be a reason your plants aren’t fruiting, more common than not in the heat of the summer is the weather. High heat coupled with extremes in humidity (extremely high or extremely low) can hinder fruit set. This happens because the pollen grains get sticky and aren’t able to fertilize like they need to.

tomato flowers with no fruit

You can try to shade your plants to offer some heat relief. But, the most likely remedy in this situation is to try and keep your plant healthy until the temperatures level out again. Then the fruit will begin setting normally again.

Splitting Fruit

If you find that your tomatoes are splitting, most of the time this occurs when a dry spell is followed by heavy rain. The water goes into the plant and the fruit are not big enough to handle it. Thus, they split. If you’ve had a dry spell and know rains are headed your way, and the tomatoes have started blushing, go ahead and harvest those tomatoes.

Cracking Fruit or Cat Facing

This is usually found on the bottoms of your tomatoes and will be a bit hard and corky-looking. This typically occurs on larger tomatoes and is usually due to cooler daytime and nighttime temperatures. It also can occur when the tomato has experienced too much pruning.

tomato catfacing

Sun Scald

While this is common on a lot of fruits and veggies that harvest in late summer, tomatoes seem to be extra susceptible to sun-scald. This is the white bleached spot on a part of your tomato caused by direct sunlight exposure to the fruit, especially when temperatures are high.

If you don’t have a way of shading your tomato plants, I suggest being very careful in how much you prune your plants. The extra leaves on those plants will help shade those tomatoes. If you are a heavy pruner (as I am not), consider shade cloth to filter the light.

Tomato Pests and Insects

Tobacco or Tomato Horn Worm

If you head out into the garden to find your tomato plant leaves utterly stripped, you’ve likely got a hornworm. While it’s hard to see these in the daytime (they’re great at camouflage!), another sign of these pests is the black corncob-looking feces that they leave behind.

handpick tomato hornworm

The best way to get rid of hornworms is to handpick them off your plants and dispose of them. In an act of desperation last year (I was leaving for vacation when I discovered the hornworm) I sprayed the tomato leaves (avoiding the flowers) with BT. I returned to find that my plants had survived and there weren’t signs of the worm.

Army Worms and Tomato Fruit Worms

Armyworms are black-colored worms, easier to spot than hornworms but treated the same. Handpick them if at all possible and as a last resort, consider using bT. Tomato fruit worms can be handled just like the others.

Beetles

While worms are super annoying, to me they are easier than the stink bugs, and the leaf-footed bugs. These are much harder to handpick, are super numerous in numbers, and aren’t generally fazed by organic insecticide.

Aphids

Aphids love new tomato plants and because of this, they can look pretty intense to the gardener’s eye, but I have never once sprayed insecticide on aphids in my garden. I have taken a water hose to them, but so many beneficial insects feed off of aphids and so I tend to keep these in my garden. I’ve seen time and time again the circle of life work itself out. Here’s more on aphid control.

aphids on tomatoes

Other Tomato Troubleshooting Resources

While this has been a long list of what could go wrong with your tomatoes, the truth is there are a lot more we didn’t cover. And since I’ve only dealt with a limited number of problems in my own garden, there’s no way I can correctly identify everything. BUT, in my research, I found a few sources that can help you out as you troubleshoot any issues you come across.

The Tomato Doctor App is an app created by Purdue University. It shows you photos of common issues to help you compare your problem to identify it.

You can also send a photo of your plant to your local extension office. I’ve done this countless times and they are always so helpful. (Find yours here.)

Lastly, I am a big fan of the book: Epic Tomatoes. This is a great reference guide with a wonderful troubleshooting section in the back.

tomato harvest

While it may sound scary to grow tomatoes, they are still the number one planted crop for a reason. Whether it’s a raw, salt-covered tomato eaten in the heat of summer or a hearty pasta dish served with your homemade tomato sauce, tomatoes are a forever fave and we can’t wait to see yours.

6 Comments

  1. I put too much calcium on my tomato plants,in a box garden. Now they are sick, twisted blotchy stems. Is there anything I can to to help.?

    1. I don’t know about calcium. You might try watering a lot to let the excess leach out, but I’m just not sure how that would work. If your plants aren’t too large, you might try changing out the soil and replanting them.

  2. I am growing tomatoes in my vegetable garden and I have seen my tomatoes are falling before they are ripe. There is no infestation of fungus or insects. What may be the reason? I heard hailstorms can be one of the reasons to make tomatoes rot early, is it true?

    1. I’m not really sure why tomato fruit would drop off early, and I also don’t know about hailstorms since I haven’t had any major ones in my garden yet.

  3. Nice article Jill. One thing about tomatoes, you can not plant them near black walnut trees which gives off Juglone, a poison to tomatoes, potatoes, eggplant and others as well. I am surrounded by big black walnut trees so last year I put them in buckets on my north side porch, thinking they would not get enough sun. I did get some but they were not as nice as they should be but better than none. In the garden, they look beautiful at first but then eventually wilt and died. The Juglone comes thru the roots and from the overhead branches.

  4. Thanks, jill for writing this beautiful article as growing tomatoes is always difficult if you don’t have the proper guide which helps you to avoid making mistakes that could harm tomato growth.

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