Tomatoes are grown by more people than any other vegetable. Millions of people put months of effort into growing juicy, flavorful tomatoes. Sometimes people love their tomato plants so much they kill them with kindness.
Can You Overwater a Tomato Plant?
Yes, you can definitely overwater a tomato plant. Tomato plants should be watered every day the first week they are in the ground. After that, they should be watered once a week and given an inch or so of water all at once. In hot climates, you may have to water twice a week to keep the soil moist. Too much water can kill a tomato plant and ruin the tomatoes.
Underwatered Tomatoes versus Overwatered Tomatoes
Tomatoes are like Goldilocks – soil moisture has to be just right. This is especially true of potted tomato plants, which depend on you for all their water and nutrients. If you do not give them enough water, the leaves will curl up to reduce the surface area that loses water to transpiration. The leaves will turn brown and crispy if they do not get water soon. The best way to prevent both overwatering and underwatering is to purchase an inexpensive moisture meter. You want the soil evenly moist all the time.
Overwatering does cause curled leaves if the roots rot. Without roots, the plant cannot take up water even if the soil is wet. If the roots rot, the tomato plant is going to die.
What Does an Overwatered Tomato Plant Look Like?
Tomatoes that are being overwatered have several symptoms. Here are the easiest to see.
As mentioned above, curled tomato leaves can signal either overwatering or underwatering. It can also be caused by diseases. Root rot destroys the tomato plant’s ability to take up water, and the leaves curl to try and conserve water. The plant dies from dehydration.
Yellow tomato leaves can signal a number of different problems: iron deficiency, overwatering, tomato yellow leaf curl virus, early blight, leaf spot, and other diseases. Leaves that are yellow from overwatering do not have any special pattern on them and turn yellow all over the plant. Tomato plants that are infected with the disease tend to have yellow spots or spots with yellow rings around them. The spots spread and engulf the leaf. The diseases tend to start with the lower leaves and work up.
Blossom end rot starts as a tan, water-soaked spot on the blossom end of the tomato. The rot can spread to cover the entire tomato and ruin it.
Overwatering In Aeroponic and Hydroponic Systems
Aeroponics is a specific type of hydroponics. In both, the tomatoes are grown in rock wool or another soilless medium that can hold the roots and absorb nutrients. Water with the nutrients the tomato plant needs is washed over the tomato plant roots in cycles, so the rock wool barely dries out between cycles. If the cycles are too close together or too long, the tomato plants will have the same problems overwatered tomato plants planted in soil have.
What Happens When Tomatoes Are Overwatered?
Overwatering tomatoes causes a host of possible problems. Here are the most common problems.
Fungal infections can infect a tomato plant in a variety of ways. With root rot, the fungus is in the soil. When the roots are kept too wet, the fungus starts to grow on them. The roots become brown and slimy, then black and rotted. The tomato plant cannot absorb water, and the leaves may curl, turn yellow, and fall off.
Damping off is when a seedling is attacked by a fungus right at the soil level. The stem rots, and the seedling falls over. Once this happens, it is always fatal.
There are other fungal infections that spread to your tomato plants when water splashes soil on the leaves. This can be when it rains or when you water and get the leaves wet. The soil contains fungal spores that will grow on a wet surface. Several days of rain or even a leaf that is wet all night can let the fungus take hold. The fungus generally starts on the lower leaves and stems. The fungus will grow to infect the plant’s vascular system and choke off the water to the leaves.
Blossom End Rot
Calcium requires water to move in the plant, overwatered tomato plants inhibit the movement of water in the plant and caused blossom end rot, you can read more details about this issue in my blossom end rot in tomatoes article.
Sour rot is caused when fungi grow and cause the tomato skin to crack. Sour rot grows on wet fruit. Radial cracking, where cracks radiate out from the stem, is caused by large swings in soil moisture.
Tomatoes that are overwatered produce fruit with few nutrients and poor flavor. The excess water washes the nutrients from the tomato, so it tastes bad and isn’t very nutritious.
Can Overwatered Tomato Plants Recover?
Overwatered tomato plants can recover sometimes. Once the roots rot or fungal infection is inside the plant, the tomato plant cannot recover. If the fungus is discovered early, a fungicide can kill the fungus on the leaves and stem and prevent the death of the tomato plant. While blossom end rot cannot be fixed on a specific tomato once it starts, the rot can be prevented in future tomatoes by reducing the amount of water you give the tomato plant.
Fixing Overwatered Tomato Plants
If a fungus is discovered early, before it gets inside the plant, a fungicide can kill the fungus on the leaves and stem and prevent the death of the tomato plant. While blossom end rot cannot be fixed on a specific tomato once it starts, the rot can be prevented in future tomatoes by reducing the amount of water you give the tomato plant.
With root rot, if the problem is found early enough, the roots can be trimmed to remove the sick and rotted parts, and the tomato plant can be moved to dryer soil. However, by the time symptoms of root rot appear, it is usually too late to do this. There is no treatment for advanced root rot.
How To Water Tomatoes Properly
You can prevent a lot of problems by watering your tomatoes properly.
Once a Week
The week after you transplant your tomato plants, they need to be watered once a day. After that, spread out the watering until you water your tomato plants once a week. Give them an inch to an inch and a half of water all at once. This promotes deep roots. In very hot climates, you may have to water twice a week to maintain even soil moisture. You want the soil to be moist, not soggy. If you grab a handful of soil and close your hand, then open it, the soil should stay compact. If the soil does not stay compacted, you need to water more. If water squeezes out of your hand when you close it, the soil is too wet. You need to water less.
If you have a container-grown tomato, you may have to water the plant more often to keep it moist. The soil should stay evenly moist all week. If you find the soil gets dry toward the end of the week, water more often. However, avoid watering so much the soil stays wet.
In the Morning
Water first thing in the morning, before ten o’clock. This gives the tomato leaves and fruits a chance to dry out quickly. Dry leaves are very resistant to fungal infections.
Keep Leaves Dry
Never water tomatoes in a way that gets the leaves or fruit wet. Wet leaves and fruit tend to get fungal infections much more easily than dry leaves and fruit. Use drip irrigation, a soaker hose, or carefully pour the water at the root level. Overhead sprinklers are not a good idea.
Other Care Notes
Tomato plants need more than water to thrive and grow lots of tomatoes. Here are some tips for great tomatoes.
- Spread mulch around your tomato plant to keep the soil at a more consistent temperature, conserve moisture, and keep the soil from splashing on the tomato plant. Mulch also protects any tomatoes that touch the soil and reduces diseases in those tomatoes. Do not let the mulch actually touch the plant but put it around with an inch or two gap between mulch and plant.
- Tomatoes need at least six hours of sunlight, but they do best with morning sun and afternoon shade. Shade cloth is an inexpensive way to protect your tomato plants and tomatoes from sun scald or from getting too hot.
- Be careful when you fertilize. Too much fertilizer will burn the roots and foliage of the tomato plant. Too much nitrogen can cause the tomato plant to grow lots of foliage but not bloom much. Most tomato fertilizers have extra calcium to prevent blossom end rot. However, as I explained above, blossom end rot may happen even if there is plenty of calcium in the soil.
- While determinate tomato plants are vines that have to be caged or supported to grow well, many people do not cage indeterminate tomato plants. I think this is a mistake. I was part of a small study that showed that indeterminate tomato plants had more tomatoes, and they were better quality, when those plants were caged.
Frequently Asked Questions
Will my tomatoes get overwatered in a self-watering container if it rains?
It depends on how much it rains. Self-watering containers allow the soil to wick moisture out of a reservoir. When it rains, the soil is wet, so it doesn’t wick moisture from the reservoir. As long as the rain has a way to drain out of the container, the soil will not stay too wet once the rain stops. If a lot of rain has fallen, be sure to empty the saucer under your pots, so there is no standing water in it.
Do tomatoes burst if overwatered?
I have never had one burst, and I have not ever known someone that has. Overwatered tomatoes can crack, and I guess they could eventually burst when the cracks go all the way through, but I think they would rot first.
Do tomato plants wilt when overwatered?
Tomato plants can wilt when the roots rot, and the plant cannot take up needed water.
Can overwatering cause tomato plants to fall over?
Yes, although this generally happens in seedlings that do not have as much tissue to support them. Older plants would die before they fell over.
In conclusion, it is easy to overwater your tomato if you are not careful. Invest in a moisture meter so you can see exactly how moist or dry the soil is. Water the tomatoes once a day the first week after transplanting but reduce the water to once a week by watering fewer days one week, then fewer still after that. Put mulch around the tomato plant to conserve water, keep the soil from splashing on the plant, and keep fruit off the ground.