Should You Water Your Tomatoes With a Sprinkler?


Tomatoes are beloved by home gardeners as they’re easy to grow and have enough fruit to support a family easily. Growing flavorful tomatoes at home isn’t difficult. As with all plants, the key to good tomatoes is to feed and water them the right way. 

You shouldn’t water your tomatoes with a sprinkler because tomatoes have sensitive foliage that becomes susceptible to disease when wet. Instead, water your tomatoes close to the roots thoroughly and deeply every time. Time your watering to keep the soil moisture consistent. 

Tomatoes are mostly made up of water, so correct watering is important to ensure a good harvest. However, improper watering can cause more harm than good, so read on to learn more about watering tomatoes properly. 

Reasons Why You Shouldn’t Water Tomatoes With Sprinklers

As mentioned, tomato plants have foliage sensitive to water, but this is just one of the reasons why you shouldn’t water tomatoes with sprinklers.

  • Diseases in wet foliage. Tomato foliage is sensitive to being wet as the water encourages bacterial and fungal pathogens leading to diseases like blight. The diseases affect the leaves, interfering with photosynthesis and the plant’s overall growth. 
  • Nutrient leaching. Watering with sprinklers, also known as overhead watering, can easily lead to overwatering, especially if the sprinklers overlap. The overwatering will lead to the leaching of nutrients beyond the reach of the roots. The lack of nutrients means that your tomato plants will struggle to grow. 
  • Reduced fruit size. Plants affected by severe diseases caused by wet foliage will produce smaller fruits than expected. The reduced fruit size is unusual and only occurs when the plants are affected by a particularly severe case of blight. In most cases, this will be accompanied by reduced yield.
  • Fruit cracking. Fruit cracking refers to the condition where the skin of the tomato splits open. The fruit inside expands faster than the skin can grow as the fruit takes up excess water in the soil. Fruit cracking typically occurs in rainy weather but may also be caused by overwatering or overhead watering from sprinklers. 

Common Diseases Caused by Wet Foliage in Tomato Plants

Wet foliage results in fungal and bacterial infection in the leaves and stems of tomato plants, but fungal diseases are more common. Here are some common diseases to watch out for in tomato plants and what you can do about them.

Septoria Leaf Spot

Septoria leaf spot is a common fungal infection found in tomato plants. A type of blight, the symptoms of this disease include dark lesions on the leaves, though they may also appear on stems and flowers. 

Eventually, the leaves turn yellow and fall off, starting with the older leaves near the bottom of the plant. This blight is encouraged by too-wet conditions propagated by overhead irrigation systems like sprinklers. 

Late Blight

Late blight is also a fungal infection that presents in the form of dark spots on the leaves, stems, and fruits of the tomato plant. You may even see the fungus growing as fuzzy white patches on the infected parts of the tomato. 

Applying fungicides containing chlorothalonil and avoiding overhead watering will protect your tomatoes from this devastating disease. 

Anthracnose

Anthracnose is a group of fungal diseases, and like the other two we’ve discussed so far, anthracnose also causes spots on the leaves and the fruits. The spots start brown and may be dotted with black as the disease progresses. 

Anthracnose in tomatoes is caused by overhead irrigation when the fruit is ripening, which is why sprinkler systems should be avoided altogether. 

Leaf Mold

Tomato leaf mold only affects the foliage. This disease causes brownish mold to grow on the undersides of the leaves, causing leaf withering and death.

Leaf mold flourishes in high humidity and spreads very easily – through wind, unclean gardening tools, and overhead irrigation. Preventive fungicides can protect your tomato plants from this condition.

Bacterial Spot

Bacterial spot is one of the only bacterial infections caused by overhead irrigation methods like sprinklers. As the name suggests, the disease begins with dark spotted lesions on the foliage and fruit of the tomato plant. 

Unlike leaf mold, where the dead leaves stay on the plant, bacterial spots cause the leaves to fall, affecting the yield indirectly. The fruit becomes more susceptible to sunburn and receives fewer nutrients overall. 

While humid conditions don’t directly cause bacterial spots, overhead irrigation systems help the bacteria spread easily and infect healthy plants. 

When Is It Okay To Use Overhead Irrigation for Your Tomatoes?

Overhead irrigation creates conditions that lead to disease and encourages the disease to spread to healthy plants. However, there are some times when you might have to mist your tomato plants. 

Helping Young Tomato Seedlings Establish Roots

Tomato seedlings can be misted to keep them hydrated while the roots are still small and struggling to grow. Like new sod, tomato seedlings need a lot of water applied, often in smaller quantities, to help them grow roots. 

But once the roots have been established, you can water the tomatoes deeply and infrequently to encourage deeper roots. 

I’ll explain more about watering for root growth in young plants in my article that explores if it’s possible to water new turf too much: Is it Possible to Water New Turf Too Much?

Increasing Moisture During Hot and Dry Weather

You might also consider misting tomatoes in extremely hot conditions, where the heat is dry instead of humid. Long periods of hot and dry weather lead to physiological leaf roll in tomatoes, and you can avoid this by gently misting them with sprinklers. 

Mist your tomatoes with a spray bottle early in the morning to give the moisture some time to dry up during the day. Avoid misting at night as pathogens will have enough time to proliferate on the leaves and possibly infect your plant.

What Is the Best Way To Water Your Tomatoes?

Watering tomatoes correctly protects your plants from disease, supports plant growth, and ensures that the plant can produce good quality and quantity of yield. 

The best way to water your tomatoes is by drip irrigation, which will water them slowly at the base, allowing the water to penetrate deep into the soil. This encourages deep root growth in tomato plants and protects foliage from moisture. Only apply a maximum of 1.5  inches (3.81 cm) of water a week. 

It is important to maintain the moisture levels of the soil while ensuring it is never dripping wet. The best way is to water your tomatoes slowly and infrequently, with enough water to keep the plants healthy. Hence drip irrigation is the ideal system for irrigating tomatoes. You can learn more about drip irrigation in my article here: The Ultimate Guide to Drip Irrigation for Raised Beds

Avoid using well or bore water for your tomatoes, as the water will increase the alkalinity of the soil beyond the pH levels that tomatoes prefer. Like most plants, tomatoes prefer a slightly acidic to neutral soil pH.

Tomato plants should be watered shortly after sunrise. Early waterings allow the plant to take up all the water necessary and use it for photosynthesis throughout the day. 

The excess water has time to evaporate, ensuring the tomatoes are not sitting in soggy soil that propagates diseases. 

Tomatoes should be well-watered, not overwatered. Add 1-1.5 inches (2.5-3.8 cm) of water every week, watering close to the ground. The soil should be well-draining, but you can reduce the necessity for watering by mulching the ground

When it comes to potted tomatoes, you may need to water them more often. Ensure that the pots are well-draining and water every day if necessary. Always check the foliage and ensure that they’re not wilting or showing signs of disease.

As noted earlier, tomatoes may be misted in extremely hot and dry weather to ensure adequate hydration. 

Final Thoughts

You shouldn’t water tomatoes with a sprinkler because tomato plants have sensitive leaves that are more susceptible to diseases when wet. You should only use sprinklers to gently mist tomato seedlings or when the weather is very hot and dry. 

The ideal way to water tomato plants is drip irrigation or any other system that waters the plants slowly and deeply near the base of the plant. The slow and deep watering ensures strong root growth, improving resilience and yield. 

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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