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How to Make a Pest-Free Potting Mix at Home

Are you tired of dealing with pests in your potted plants? Pests can be a real nuisance when you start seeing them around the house–or worse, find that they’ve ruined your plant. If you’re looking for a fresh start with a new batch of homemade potting mix that is naturally pest resistant, you’ve come to the right place.

Pest-free potting mix can be made by including sand, coco-coir, diatomaceous earth, and neem oil in your potting mix. Sterilization by baking at 180-200 F will eliminate any pests and their eggs in your soil. Proper storage and watering will also minimize any chance of future infestation.

Now that you have some idea of how to make this mix, let’s take a closer look at each step in the process.

Creating a Pest-Resistant Potting Mix

As you might expect, the first step to creating a pest-resistant potting mix is choosing the right ingredients for your mix. 

There are a few key ingredients that will help keep the pests away:

  1. Sand – This will prevent pests from nesting in the soil when added as a layer on top of your soil. Since it drains water quickly and doesn’t have any decaying organic material, pests like fungus gnats will look elsewhere to find their home.
  2. Coco coir – This is a type of organic matter made from coconut husks that is naturally resistant to pests because there isn’t much decaying organic matter for them to feed on.
  3. Diatomaceous earth – This is an organic pesticide that comes in the form of a fine powder made from ground-up diatomic fossils. The individual powder particles are abrasive and can damage the respiratory systems of insects. It also dries out the mucous membranes of any breathing holes on small pests. Sounds scary, but don’t worry, It’s completely safe for small animals and people. A few tablespoons of this sprinkled into the mix will suffice. 
  4. Neem oil – This is a natural vegetable oil extracted from the seed kernels of the Neem tree. It deters pests by interfering with their hormonal systems, making it harder for them to grow and lay eggs. Other components of neem oil can also hinder pests’ ability to feed. You can add a few drops to your mix directly or, more commonly, mix it with water whenever you water your plants. 

These are the main components that will help repel pests, but you’re also free to add other soil components as you like (i.e. vermiculite to improve the aeration of the soil). You can even mix in any potting mixes or potting soils that you already have on hand.

If you are going to purchase some additional soil to add to this mix, I would recommend getting potting mix as opposed to garden soil.

Most store-bought potting mixes should already be sterilized, unless the packaging was damaged. On the other hand, garden soil is just untreated dirt and there will likely be mold spores and possibly insect eggs. 

Here is a basic recipe for a soil mix that includes these ingredients:

  • 2 parts potting mix
  • 1 part coco coir
  • 1 part perlite or vermiculite
  • 2 tablespoons diatomaceous earth
  • 2-3 drops neem oil mixed in a cup of water
  • 0.5-1 inch (2.5cm) of sand layered on top of the soil after planting

You can always adjust the proportions of these ingredients to suit your needs. If you’re not sure if the proportions will work for your plants, you can also test a small batch before using it on all of your plants.

How to Sterilize Your Soil

Before you use your mix on your plants, it’s always a good idea to sterilize it a few hours ahead of time. Especially if you are including garden soil or some old soil that you’ve mixed with your new batch.

This will eliminate any pests, their eggs, disease pathogens, and fungus spores that may have made their way into your soil since you last checked it.

There are a few main ways you can sterilize your soil:

  1. Baking it in the oven
    1. Pour your soil mix into a baking pan and cover it with aluminum foil. 
    2. Pre-heat your oven to 200 F.
    3. Place your soil mix in the oven with a thermometer inserted to measure the temperature
    4. When the thermometer reads 180 F, start a timer for 30 minutes
    5. Remove your soil after 30 minutes and let it cool to room temperature
  2. Soak in hydrogen peroxide
    1. Mix ½ cup of 3% hydrogen peroxide per gallon
    2. Add the solution to a spray bottle to evenly moisten the soil.
    3. Spread out your mix onto a baking pan or other flat surface
    4. Spray your soil mix until it is evenly moist (not soaking wet)
    5. Wait 3-4 hours before planting with your soil
  3. Use a steamer
    1. Pour your soil into a heat-safe container up to 4 inches (2.5 cm) deep without pressing it down
    2. Add a few cups of water to the bottom of your steamer
    3. Place your soil into the steamer 
    4. Start the steamer and set a timer for 30 minutes once it starts to boil
    5. Remove your soil after 30 minutes and let it cool to room temperature

After you’ve planted your plants with your sterilized soil, you will want to let the soil dry out completely between watering to avoid fungus gnats, which is the most common pest for indoor plants.

How to Store your Potting Mix to Avoid Pests

The best place to store your potting mix is in a sealed, airtight container. This will ensure that no pests or mold spores can break through and access your soil.

It’s also important to consider how you are adding the soil to the container. Ideally, you want to have a completely sterile environment while you do this. This goes for both the container and also your soil. 

Before adding your soil to your storage container, make sure to sterilize it with one of the methods we’ve gone over above.

For your storage container, a simple way to sterilize it is to wipe it down with alcohol. Alternatively, you can soak it in a solution of 1 part bleach and 9 parts water for 30 minutes before scrubbing it down and rinsing it with water.

While you are sterilizing your storage container, it’s also a good idea to do the same with any tools you are using to transfer the soil. 

Once you’ve transferred the soil and sealed off your container, it’s a good idea to store the container somewhere that’s sheltered from the elements, like your garage or a backyard shed. This serves as an extra layer of protection against any pests or mold spores. 

By following all these steps, you can greatly reduce your chances of running into problems with pests (fingers crossed).