The main problem in gardening is not having the best soil to sow seeds. but what if I tell you that you can use your old potting soil or any soil for growing plants.

To use any garden soil all you need to do is sterilize the soil before use.

The question is how to sterilize potting soil.

In this post, I will tell you how I sterilize potting soil and reuse it in new pots.

What are the problems with the soil?

Every gardener face problems with potting soil. You have two options one is to buy new potting soil every time you want to sow new seeds. The second is to sterilize your garden soil and use it in new pots for planting new seeds.

The following are the main problems with most garden soils.

Fungal Gnats

These are tiny insects and are big problems for every potting soil. Even sometimes they can be seen on newly purchased potting soil. They hide in the soil and double their population in days. This is one of the biggest issues with the soil.


The weed seeds are commonly found in almost every garden soil. All types of gardens are struggling with weeds. Each year many gardeners use different chemical-based liquid weed killers. But this weed is so stubborn that it comes out of the soil every year. Weed suck all the nutrients from the soil and plants become nutrient deficient. 60% of the given fertilizers get sucked by the weed.

Fungal Bacteria

The soil also contains many types of fungus and mold in hot and humid conditions. Fungus in the soil is the main cause of plant root rot. So, it is highly important to check the soil to identify fungus and mold in it. If you don’t know how to check the soil for fungus don’t worry. Because sterilization is the process that kills the fungus causing bacteria and gives clean soil.


If you ever use animal manure in your garden then your garden soil surely contains pathogens. These pathogens are deadly for plants as well as for humans. When vegetables are grown in pathogen contain soil. They affect the vegetables and can enter into your system on touching or eating those fruits and vegetables.

How to sterilize potting soil at home?

sterilize soil

The easy and affordable way to kill pathogens and bad bacteria in the soil is to sterilize it at home. For sterilizing the soil use boiling water.

It doesn’t matter you are using a few cups of your garden soil in a seedling tray. Or you need soil for 10 pots. It is best to sterilize it before use. Take the desired amount of soil put it in the bowl and add boiling water to it. This hot water kills insects, fungus, and pathogens in a few seconds. You will see them on the surface of the soil.

Another way has put the bag of soil in your fridge for a few days. This reduces the life cycle of pathogens and insects. But I don’t recommend this idea because you don’t know how many types of bacteria your soil contains. And putting it in the fridge where you store your food is never a good idea.

For safety stick to the boiling water method or you can use some professional soil sterilization methods like below.

How to sterilize potting soil with other methods?

Below are some guaranteed soil sterilization methods.

Steam Sterilization

This method also uses water as the primary substance for the sterilization of soil. Take a pan to fill it with water and put it over the gas stove and turn it on. Now make the layers of soil in a rack above it. Close the lid of the pan and leave it on the stove for 30 minutes.

When the water starts boiling it produces hot steam. This steam comes out through tiny holes and is enough to kill insects and deadly pathogens.

I know this is a time-consuming idea. And if you want a large amount of soil to be sterilized then this idea is not considered to be the best.

Use Oven

how to sterilize potting soil

Another good and affordable method of soil sterilization is using your Oven. Yes, you can sterilize your garden soil or any other potting soil in your oven. Take the oven-safe container and layer the 4 inches of soil in it. Then cover it with the foil paper and put it in the oven. Turn it ON and set it to 180 to 200-degree F.

The problem in this method is the overcooking of the soil. Because over-cooked soil produces toxins and they are not good for your plants. To avoid this problem, place the oven thermometer in the oven. Once the temperature rises to 180-degree F turn the oven off and take out the soil container.

Do not uncover the soil the right way leave it covered for 30 minutes and then remove the cover. Use the soil when it gets cool and come at room temperature. Don’t forget to wear oven gloves.

Use Microwave to Sterilize Soil

Soil sterilization

In order to use the microwave for soil sterilization, you need to moisten the soil. It is important to avoid overcooking of the soil. Take the microwave-safe container and put the soil in it and place it in the microwave.

Turn it ON and set the microwave on high settings for 90 seconds. Make sure you cover the soil container with the lid that has holes. So that the steam can come out easily.

For 3 pounds of soil run your microwave for 90 seconds.


Most hobby gardeners plant seeds in the soil without sterilizing it. Sterilizing the soil is an important part of indoor gardening. Whenever you want to grow plants in pots, raised garden beds always sterilize the soil before use.

Soil contains fungus, pathogens, and harmful insects. Even the new packed potting soil can have insects in it along with pathogens.

Therefore, for the safety of your family and plants always sterilize potting soil before use.