If you’ve ever lost tomato plants in your garden, you know how frustrating it can be to see all your hard work go to waste. It is even more frustrating when it happens year after year.
So, why do your tomato plants always die? Watering your tomatoes too much, too little, or even at the wrong time of day can kill your tomato plants. Incorrect nutrient or pH levels in the soil can also kill your tomato plants. Extreme temperatures, disease, and pests are all potential tomato plant killers.
There is a lot more to keeping your tomato plants alive than adding water and nutrients. Luckily, there are ways to give your plants a better chance of survival. Let’s get look at some of the reasons that your tomato plants may be dying, and how you can treat or prevent these problems.
Improper watering is a common cause of dying tomato plants. Believe it or not, over watering is just as much of a problem as under watering.
When you underwater your plants, they have some ways to survive for a while. For one thing, they may have some water stored for a dry spell.
They can also slow down their growth, or wilt their leaves to prevent the sun from drying them up. However, if you go on a week’s vacation in July and forget to ask someone to water your garden, your tomato plants will be in trouble.
If you struggle with keeping your soil wet, check out my article on how to treat dry soil.
On the other hand, when you over water your plants, the soil around the roots becomes too wet and stays that way. After a while, the roots begin to rot, since they cannot get rid of water quickly enough to dry out the soil.
This can happen if you water your plants heavily and then get a heavy rainstorm, so be sure to check the weather forecast and water accordingly.
For more information, check out my article on over watering plants.
How Much Should I Water My Tomato Plants?
There is no solid rule to use for the amount of water to use – it will depend on where you live, the season, the weather, the size of the plant, and even your soil. A better way to tell is to stick your hand in the soil.
If it feels dry a couple of inches down, then you can water your plants. If the soil is moist or wet, then there is no need to water.
Remember These Tips When Watering
There are a couple of other things to remember about watering. First, it is better to water less frequently and give your plants a deep drink of water that will get to the roots, rather than several shallow drinks that may be evaporated by the sun.
Also, water the plants low, close to the soil. Avoid getting water on the stem or leaves – this increases the chance of mold, fungus, or rot on the tomato plant.
Finally, the best time to water is early in the morning, when the sun is low and the air is cooler. That way, the water will go to the roots, instead of evaporating.
In short: don’t kill your plants with kindness by over watering. You can always add a little more water to the soil if needed, but it’s hard to take it back out!
Incorrect Soil pH
If you think your watering regimen is ok, then checking your pH is a logical next step. If your pH is too high or too low, then your plant can suffer from a nutrient deficiency. This can occur even if there is plenty of the nutrient in the soil! The reason is that when soil pH is too high or too low, then nutrients will be less available for the plant to absorb through its roots.
You can buy a soil pH test kit online or at a local garden center and do it yourself. You can also take a soil sample and send it to your local agricultural extension for testing. For more information, check out my article on testing your soil.
An ideal pH range for many plants is 5.5 to 6.5 (slightly acidic – a pH of 7.0 is neutral). Some plants, like blueberries and azaleas, like more acidic soil.
If your pH is way off, you can adjust the pH for next season by adding lime (to increase pH) or sulfur (to lower pH). These are not the only ways to adjust pH, and you can find additives that will adjust pH while also providing nutrients for your plants. Speaking of which, let’s talk about nutrients and possible deficiencies.
As mentioned before, a plant’s ability to absorb nutrients through its roots is affected by soil pH. Even if your soil pH is in an acceptable range, there are other things that might cause nutrient deficiencies in your plants.
For one thing, cold soil can cause your plants to absorb nutrients more slowly. This could be a problem if you plant too early, or if you get a prolonged period of unseasonably cold weather.
It could also be a problem if you put plants in your garden that are not appropriate for your climate. For more information, check out this article on the USDA site about plant hardiness zones.
Another possibility is a nutrient imbalance in your soil. For example, too much calcium can prevent your plant from absorbing magnesium – even if the soil contains plenty of magnesium. Gardening is all about balance, so make sure that you are not consistently adding too much of one nutrient.
It is also possible to over fertilize your soil, such as with too much high-nitrogen fertilizer. For more information, check out my article on over fertilizing and my article on low-nitrogen fertilizers.
Again, a soil test kit is a good way to find out if you have a nutrient imbalance.
Lack of Nutrients in Garden Soil
A soil test may also reveal that your soil is lacking a nutrient. Your plants will also tell you – if your leaves turn yellow, this is one sign that you may have a nutrient deficiency in your soil.
For more information about some of the most common nutrient deficiencies, along with ways to diagnose and treat them, check out these articles:
Damage During Transplanting
Some gardeners like to start plants from seeds indoors, and move the seedlings outside once they are grown a bit. Others like to buy established plants from a garden center.
Either way, your plants may be damaged when you transplant them outside. For one thing, the roots could be burned by the sun if you leave them exposed too long.
If you have dozens of plants, take a few outside at a time and plant them, and then go back inside for more. You can also put your plants under something that will shield them from the sun. Just make sure it doesn’t get too hot under the sun shield, or you will lose the plants anyway!
The sun is not the only thing that can damage the roots of the plant. When you put a tomato plant in the ground, make sure not to damage the root system by crushing the roots or cutting them off with a trowel.
Finally, make sure to give the plants some water after transplanting. They won’t be used to full sun, and they will need water to survive.
Another neat trick is to bury your tomato transplant deep, up to 2/3 of the height of the plant. To learn more, check out my article on why to bury tomato plants deep.
As mentioned earlier, cold soil can inhibit a plant’s ability to absorb nutrients. Extreme heat and humidity can also kill a plant, since its ability to transpire (move water from the roots to the leaves and into the air) will be limited. Since transpiration helps to cool a plant, this can lead to overheating and death.
If your plants seem to die during the hottest days each year, try moving them to a location with less daylight sun for next year. Generally, the most intense sunlight occurs in the hours around noon time.
Too Much or Too Little Sunlight
Tomatoes need at least eight hours of sunlight per day to be healthy. Too much sun can dry them out or stress them, leading to death, especially if you make some other mistakes (not enough water, etc.) Too little sun will not allow your plants to grow and produce fruit like they should, although shade may not kill them.
There are many plant diseases that can kill tomatoes including:
- Tomato blight (either early or late)
- Wilt (fusarium or verticillium)
- Tomato Spotted Wilt Virus
If your plants are turning black on the leaves, stems, or fruit, then you will want to find out what the problem is and treat it if you can. For more information, check out my article on black spots on your tomato plants.
The best way to prevent these diseases is to select crops that are resistant to them. If some of your plants are already affected, you might have to remove them to prevent the spread of disease to the rest of your plants. Leave enough space between your plants to prevent disease from spreading easily.
Some of these plant diseases can survive in the soil over the winter, so affected areas may need to remain unplanted for a year or more to treat the problem.
There are a multitude of garden pests that can kill your tomato plants, or at the very least, reduce your harvest by weakening your plants.
Some common pests that are a scourge to tomato plants include:
- Tomato Hornworm
There are both organic and chemical ways to prevent and combat these pests. For more information, check out this article about how to get rid of cutworms in your garden and this article on how to get rid of aphids.
By now, you should have an idea of which problem is causing your tomato plants to die. Hopefully, you also have a starting point for a plan to help them recover, or to prevent the problem in the future.
I hope this article was helpful. Please leave any questions in the comments below.