How to Sterilize Soil for Houseplants

Thriving in the layers of most soil are pests and pathogens that are silently taking the life out of our plants. The best way to get rid of them is soil sterilization. So, how do we sterilize soil for houseplants?

You can sterilize soil in a number of ways, varying from natural methods, such as sunlight and steamed heat, to chemical ones. The process will basically eliminate unwanted pests and harmful microorganisms residing in the soil of your houseplants.

If you’re interested in knowing the different methods of sterilizing the soil, this article is perfect for you.

Everything You Need to Know About Soil Sterilization

If your plants are dying quickly, it’s a looming sign that something deep within its root is silently committing a crime. That is, feeding through your plant’s roots and stealing their nutrients.

The culprits are nematodes, pathogens, bacteria, and other pests. Some of these creepy crawlies may also roam in your house, and that’s something we want to avoid.

To get rid of them, you’ll have to expose your soil to a sterilization process or heat the soil to kill the pests.

Now, it’s important to note that once you decide to sterilize your soil, not only will you eliminate the bad microorganisms, but the good ones too. Nonetheless, you can still supplement your sterilized soil with nutrients later on.

Methods on How to Sterilize Soil for Houseplants

If you decide to sterilize your soil, there are some effective methods you can choose from:

Method 1: Hydrogen Peroxide

Spraying hydrogen peroxide

Using hydrogen peroxide as a means of sterilizing your soil will serve two purposes.

The first one is it’ll effectively eliminate pests, bacteria, and fungus gnats that are causing damage to your plant’s root system. Second, your plant will benefit from this since hydrogen peroxide contains oxygen which promotes healthy growth for your plant’s roots.

It’s pretty simple to do too. Hence, it’s one of the best methods to use in sterilizing your soil.

To do this:

  1. Protect your skin by using a pair of gloves before the process.
  2. Prepare hydrogen peroxide at a three percent concentration. Don’t get something higher, since it can harm your plants.
  3. Pour the right amount of hydrogen peroxide into the sprayer filled with water.
  4. Note that for each gallon of water, you’ll need ½ cup of hydrogen peroxide.
  5. Moist the soil in a peroxide solution.
  6. Stir it to distribute the peroxide solution on all layers of the soil.
  7. Finally, cover it with an air-tight cover and let it dry for about 24 hours before using it.

Also Check: 10 Common Houseplants That Love Acidic Soil

Method 2: Solarization

If you prefer a more natural approach to sterilizing soil for houseplants, you can try this method of exposing your soil to the sun’s heat.

Here, you’ll be covering your soil with layers of transparent plastic and leaving it under direct sunlight. This will build up a temperature that’ll eliminate most of the bacteria and pests present in the soil.

Here’s how the process works:

  1. Lay down your initial layer of plastic, then place the soil evenly on top of it.
  2. Keep the soil at least six inches away from the edge.
  3. Break up clumps of dirt, leftover plant matter, and large rocks that can slow the heating process.
  4. Wet the soil until it’s moist.
  5. Cover it entirely with another layer of transparent and quality plastic bags or sheets.
  6. Place some stones or pegs to secure the cover.
  7. Check that it’s tightly closed so the air or breeze has nowhere to pass through.
  8. Expose it under the sun and let it sit there for a month or so.

Method 3: Oven

This method is a good choice if you’re going to sterilize a small amount of soil and you plan to use it instantly. It’s quick and simple. However, the downside of this one is it’ll fill your kitchen with an odor you probably won’t be a fan of.

As such, you’ll need adequate ventilation if you want to try this process. Here’s how this method works:

  1. Prepare your soil in a tray. It shouldn’t be deep, so heat can penetrate through all parts of the soil.
  2. Pour a few cups of water into the soil just enough to moisten it. This will create steam that’ll kill the contaminants.
  3. Cover your tray or container with aluminum foil so it won’t dry out ahead of the process.
  4. You may use a meat thermometer to measure the temperature of the soil.
  5. Bake the soil at 350 degrees for about 20 to 30 minutes or until the meat thermometer hits the target at 180 degrees Fahrenheit.
  6. Turn off the oven and let the soil cool down for a few hours..

Related: 11 Amazing House Plants That Don’t Need Soil

Method 4: Steamed Heat

In this method, you’ll need a steamer pot or a wire cooking rack which you’ll lock into a larger pot. You’ll basically let the soil sit to allow heat and steam to penetrate through it.

To do this, follow these steps:

  1. Drop two to four cups of water in the pressure cooker.
  2. Put the soil in a heat-safe container and cover it with foil.
  3. Keep the depth of your soil to lower than four inches and don’t press down the soil just to make it fit.
  4. Lock the steamer pot or cooking rack on top of the larger pot, then cover it.
  5. Turn your pot on a high flame and let your soil sit for 30 minutes. The boiling water will find its way to the soil and sterilize it.
  6. After 30 minutes, turn it off and let the heat subside before using the soil.

Method 5: Grill

If you don’t want your kitchen to smell bad, you may try heating your soil with a grill instead. The good thing here is that you can do this outside.

To carry out this method, follow these steps:

  1. Line an unused pan with foil.
  2. Pour soil into the pan.
  3. Add a little water to dampen the soil.
  4. Cover the top of the soil with a second layer of foil to keep everything in place and to avoid it from drying out.
  5. Use a meat thermometer to measure the temperature of the soil.
  6. Turn on the grilling to the hilt for 30 minutes.
  7. Once the thermometer hits 180 degrees Fahrenheit, turn it off and let it rest for a few hours.

Method 6: Boiling Water

Boiling water

If you don’t like the idea of placing soil in your oven, cooking pot, or grill, then this method is perfect for you. Besides, it’s rather easy and cost-effective.

By pouring boiling water into the soil, the insect eggs, fungus gnats, and other unwanted guests will die. It’s a little risky though, since you’ll be dealing with high temperatures, which may burn your skin. So, be pretty careful.

Here’s how this method works:

  1. Pour the soil into your preferred container. Just make sure that your container has sufficient space for the mixture.
  2. Heat water in a pot and wait until it reaches its boiling point.
  3. Note that the amount of water to boil is dependent on the amount of soil you’re going to sterilize. In a nutshell, if the soil you sterilize is of a small amount, the water you’ll pour should also be just enough.
  4. Once you’ve boiled the water, gradually and carefully pour it into the soil. The soil should appear damp but not saturated.
  5. Mix it with a wooden spatula for heat to go through the bottom of the soil.
  6. Cover the container with aluminum foil to agitate and trap heat in the soil, eliminating pesky pests in the process.


Learning how to sterilize soil for houseplants is important since it’s one way of protecting your plants from harmful and destructive microorganisms.

As a result, you’ll increase the likelihood of your plants getting the optimal growth it needs.