Uses of Baking Soda in Cannabis Gardening

Stephen Andrews
05 Oct 2022

Believe it or not, baking soda can help you do miracles in your garden. Whether you are growing Cannabis, vegetables, or other crops and flowers, sodium bicarbonate can be used as a spray to combat powdery mildew, eradicate black spot fungus, and control leaf fungus and soil gnats, to name just a few of its benefits. It can also help deter pesky critters, eliminate unwanted grass near cultivated plots, or remove coatings with undesirable substances such as nutrients and pesticide spills. Keep reading to learn more about the various benefits of using baking soda solutions in your cannabis garden.

Bicarbonate of soda is a known baking ingredient. It gives bread, pastries, muffins, and cakes their distinctive fluffy texture. Soda powder is reactive with acids like lemon juice and vinegar, which causes the dough to rise by producing carbon dioxide. 

Besides being a popular kitchen supplement, baking soda can also be used for multiple other things around the household. It helps suppress a foul fridge odor; it can be used as a kitchen cleaner and a whitening agent for laundry. You can remove carpet stains with it, and you can even use it as a teeth whitener or as a mouthwash. 

In cannabis gardens, baking soda can be an effective pest control agent. It can help treat plants in the vegetative or early stages of flowering. The foliage might need a gentle rinsing if you notice a residue after applying your solution. Like other garden supplements, soda solutions should not be used when plants have advanced into the flowering cycle. 

Below, let's skim through the various uses of baking soda in your cannabis garden. 

How to Use Baking Soda for Fungal Plant Diseases?

Depending on the fungal spread you detect, several different baking soda solutions or sprays can be prepared. 

Powdery Mildew

Powdery spots commonly affect gardens with high levels of humidity. Soda bicarbonate can help you remove mildew attacking your plants or even vegetables. Baking soda acts as a fungicide by disrupting the ion balance in fungal cells. What you need to do is prepare a simple solution that you can use to spray the foliage of your cannabis plants.

Powdery mildew solution ingredients:

  • 1 tbsp. of baking soda
  • 1 tbsp. of dishwashing liquid (or half tbsp. for a lighter concentration)
  • 1 tbsp. of vegetable oil (for surfactant purposes)
  • 1 gallon of water


  • Outdoor cannabis plants: spray weekly when the sky is gray. In combination with sun, soda may cause foliage burns. 
  • Indoor cannabis plants: apply when the lights are off and plants are cool. Switch on the lights again after the plants appear dry. 
  • If needed, shake the excess moisture from the foliage before turning back the lights on or before moving the plants to direct exposure to sunlight. 
  • Ensure that the solution is very well diluted before use.
  • The spray can also be used for washing vegetables and other garden flowers, including zinnias, impatiens, squash, cucumbers, etc. 

Leaf Fungus and Soil Gnats

Before applying anything, partially defoliate your cannabis plants by removing the worst affected leaves. As per the solution, prepare four teaspoons of baking soda with one teaspoon of castile soap in a gallon of water. Combine thoroughly and treat affected foliage and soil as needed. 

Alternatively, mix a gallon of water, a tablespoon of baking soda, and two tablespoons of vegetable oil, then add half a teaspoon of castile soap to prepare an anti-fungal spray for Cannabis. Spray with this solution until the fungus disappears. The same spray can be used for tomato plants. 

Black Spot Fungus

If your plants are attacked by black spot fungus, a very simple solution is used for spraying and washing. Mix four teaspoons of baking soda with a gallon of water and apply it to the plants. Again, avoid use when plants are exposed to heat and sunshine. The baking soda water spray can also be used on roses and grape vines, but only in the early fruiting stage. 

greenhouse garden with visible tomatoes and other plants.

How to Kill Bugs with Baking Soda?

Sodium bicarbonate can also deter various types of insects, including sap-sucking varieties, caterpillars, carpenter ants, and silverfish.

Sap-sucking pests

A solution of two tablespoons of baking soda and two tablespoons of organic, bio-degradable soap stirred in two cups of water can work as an excellent deterrent. Using natural soap solutions is strongly advised so as not to harm the growing environment with chemicals. 

Begin by applying small doses of the spray solution if your plants are young. A more potent dose may harm the leaves, especially if they already appear weaker due to infestations. Spray plants weekly or as needed, such as after rainfall in outdoor gardens. Wait until the lights are switched off for indoor plants. 


Prepare a fifty-fifty blend of baking soda and regular flour, then apply directly onto the plants. The caterpillars will munch on it and consequently die in a matter of days. If they return, repeat the application. 

Other critters

Create pest-free grow spaces by sprinkling a perimeter of soda powder along doorways, windowsills, and around plumbing fixtures, under sinks, or any area around the house where you notice interlopers such as ants, cockroaches, silverfish, and similar bugs. The critters will not make it cross the line. Slugs may be controlled by applying baking soda directly to the invaders themselves. 

How to Eliminate Pesky Weeds? 

Unwanted greenery, the likes of crabgrass, bindweed, and nutsedge often invade outdoor plots, sometimes creating an inviting environment for all sorts of bugs and insects. There are plenty of natural remedies for removing unnecessary grass; baking soda is one of them. 

Soda powder will eliminate existing weeds and prevent new growth; however, it should be applied with caution if near Cannabis plants and cultivated grass plots. Remember that this treatment is most effective for actively growing weeds, such as during spring or fall seasons. In the summertime, when weeds need more vigilance, soda may not be as effective. 

outdoor cannabis plants.

How to Fix Other Plant Damage with Baking Soda? 

Occasionally, growers have to deal with the removal of various types of deposits that might coat cannabis plants. Excess nutrient or pesticide spills, bad weather, or nearby construction efforts can all contribute to coatings that  jeopardize key metabolic processes such as photosynthesis and transpiration. 

A mixture of one teaspoon of baking soda, one teaspoon of Epsom salt, and half a teaspoon of clear ammonia with a gallon of water can help solve issues with harming coatings. 

The mixture should be sprayed freely over outdoor Cannabis plants, particularly if rain is forecast. This method can also be used to clean indoor plants, but making sure not to saturate them and rinsing them afterward to keep the foliage fresh. 

Attention needs to be paid not to overdose the soil. Otherwise, you will need to flush the soil to clean it from excess salt deposits. The soil may already contain high amounts of salt if you live near the ocean. Therefore, keep that in mind before applying baking soda to your cannabis garden. You don't want to drastically alter salt contents as it will affect soil conductivity, which is not good for Cannabis growing (pH 5.8 to 6.8).

How to Test Soil with Soda Powder? 

There's a simple baking soda test that you can try if you want to check whether acidic soils downplay your gardening efforts. Sprinkle a bit of sodium bicarbonate onto the dirt in your growing plot when it's wet. If bubbles appear, your soil is acidic (pH <5), which may explain why your plants are not performing as they should. 

Can You Clean Garden Tools with Baking Soda?

Cleaning is one of the many hundreds of uses of baking soda in the household. Add just enough water so that the soda mixture has the consistency of hand gel. Most grower tools, such as watering cans, clay pots, sprayers, and plant containers, can be scrubbed and rinsed with the soda powder paste. The same solution is great for cleaning your hands from the dirt after a long day in the garden or for removing the odor at the bottom of trash cans and other smelly places.

Happy growing and gardening!

Stephen Andrews