Should You Use Baking Soda For Tomato Plants?

Should You Use Baking Soda For Tomato Plants?

A question I get asked often is “Should you use baking soda for tomato plants?” What are the benefits and are there any drawbacks?

I wrote an entire article outlining a range of uses for baking soda in the garden. In it. I do mention that baking soda can be useful for tomatoes. Not only can it get rid of unwanted pests but it can also help to prevent fungal diseases such as leaf spot, black spot and early blight.

So, I thought we would discuss this in more detail so that you know the benefits of using this kitchen staple on the tomatoes growing in your garden. 

*This website is reader-support so this post may contain affiliate links for which I earn commissions.*

What Is Baking Soda?

a jar of baking soda on a table with half a lemon beside it

You probably already know this, but baking soda is just sodium bicarbonate. It’s made up of:

  • 57.1% Sodium
  • 27.4% Oxygen
  • 14.3% Carbon
  • 1.2% Hydrogen

Note the high sodium content which indicates that you really need to use this product sparingly around your plants. Too much sodium or salt can burn the roots of the plants, so using less is always better. 

The 3 Main Benefits Of Using Baking Soda Around Your Tomatoes

The three main benefits that you’ll get from using a small amount of baking soda around your tomatoes are all focused on pest and disease control such as fungal infections.

Let’s look at pest control first and then we’ll explore a couple of tomato diseases that could devastate your crop.

Use Baking Soda To Get Rid Of Pests

large green hornworm on a tomato leaf

There are plenty of garden pests that may love your tomatoes as much as you do. These include:

  • Aphids
  • Snails
  • Slugs
  • Hornworms

Baking soda can be quite useful in killing these pests and protecting your precious tomato plants. So, how should you use it?

  • Sprinkle a small amount of baking soda around the base of your tomato plants
  • Make a mixture of baking soda and water to spray on your plants
  • Put some baking soda into your snail traps to kill them instantly

With all these methods, don’t use too much baking soda at one time. Remember the high sodium content! 

If in doubt, it’s better to err on the side of caution and use less rather than more. For example, when sprinkling around your plants or mixing the baking soda into a spray, try to use no more than 1 tablespoon of baking soda at a time.

For the spray, this should be mixed with around 1 gallon of water (4 litres) so that the baking soda is well-diluted.

Using Baking Soda To Prevent Powder Mildew

tomato leaf with powdery mildew

Powdery mildew is one of those fungal plant diseases that’s extremely difficult to get rid of once it takes hold. Therefore, prevention is the key and the best way to avoid disaster.

If your plants are likely to be infected with this very annoying fungus during the growing season, treat your tomatoes early so it doesn’t get a chance to infect them.

Just make a spray using 1 tablespoon of baking soda with 1 gallon (4 litres) of water and add a teaspoon of gentle dish soap. The soap will help the concoction to stick to your plants. Alternatively, you can replace the dish soap with vegetable oil which serves the same purpose. Use this to spray your plants all over.

Make sure that you only spray your plants on a cloudy or overcast day so that you don’t end up burning the foliage. 

Using Baking Soda To Prevent Blight

tomato leaf with late blight

All tomato blight diseases, like early blight and late blight, are either bacterial or fungal. They tend to infect your plants during the flowering and fruiting period.

Blights show up as brown spots on the leaves, usually starting with the older leaves near the base of your plants. If left untreated, not only will these diseases affect the older leaves, but they can move onto the newer foliage and eventually kill the entire plant.

However, you can use baking soda as a preventive so that blight does not infect your plants.

How does this work?

Baking soda is alkaline in nature and these diseases do not like an alkaline environment. So, by making a diluted baking soda spray and spraying your tomato plants with the solution, like the one mentioned above for controlling powder mildew, you’ll save your plants from getting infected by the fungal spores

However, if the disease has already taken hold, the baking soda solution will not kill it off.

Can Baking Soda Really Result In Sweeter Tomatoes?

healthy tomato plant with lots of red fruits

This is one of those common beliefs that has no real tried and tested truth to it. But, I can help you understand the science behind it. This will explain why some experts say that baking soda can sweeten tomatoes while others will state emphatically that it doesn’t

In all honesty, the tomatoes I’ve grown have always been lovely and sweet. I think this is because I use good sustainable gardening practices.

For example, I like to top up my garden beds with well-aged compost before I plant tomatoes each year. I also tend to try and grow my tomatoes in alternative spots to last year. Plus, I ensure that they get plenty of direct sunlight and ample amounts of water.

So, what’s the science behind this claim? Because baking soda is alkaline, it can help to reduce the acidity or raise the pH of the soil. It’s believed that more alkaline soil will produce sweeter tomatoes.

Unfortunately, that’s a myth that has no actual foundation in science. Also, it actually does take quite a long time for the soil pH to alter and for acidity levels to change. It just doesn’t happen straight away.

Other Myths About Using Baking Soda On Tomatoes

There are a couple of other myths about the use of baking soda on tomatoes. Let’s dispel these once and for all.

Baking Soda Encourages Flowering

flowers of a tomato plant

Most of you who read my articles regularly should understand that this is just not the case.

What promotes flowering and fruiting? Potassium, I hear you say. Congratulations, you’ve been paying attention and you know that there are just three major nutrients that are responsible for plant growth.

While macronutrients such as calcium, magnesium and yes, even sodium, are necessary, they’re only used by plants in minute amounts. And, if there’s a lack of any of these in the soil, you will see some evidence of this in the plant growth and colour.

Using Baking Soda Is A Good Way To Kill Weeds

large tomato growing patch in a garden

Baking soda does indeed kill weeds. But, this doesn’t mean that you should use it to kill the weeds around your tomatoes.

Remember the high sodium content? Not only will this do a fantastic job of killing all those pesky weeds but it will also kill your tomato plants in the process.

You see, the salt will get washed into the soil around your tomatoes and effectively burn the roots of your plants. The only way I would weed around my tomato plants is by pulling the weeds out by hand.

Frequently Asked Questions

Can too much baking soda hurt my tomato plants?

Absolutely! Remember that baking soda is extremely high in sodium so it must be used sparingly around your tomato plants to ward off pests and diseases.

How much baking soda is safe for tomato plants?

Never mix more than 1 tablespoon of baking soda with 1 gallon (4 litres) of water when using the mixture on your tomato plants.

Can baking soda burn tomato leaves?

Yes, that’s why you should only spray your tomato plants when it’s cloudy or overcast and never in the heat of the day when the sun is blazing.

Final Thoughts

Baking soda is one of those staples that everyone has in their kitchen cupboards. But, it also has plenty of uses in the garden. Even, for your tomato plants. It can be highly effective at getting rid of pests and preventing diseases from infecting your plants.

However, make sure that you only use it in small amounts so that you don’t hurt your precious tomato plants.

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