Can You Sterilize Soil With Boiling Water?

The GardenSpring |

If you like to garden, at some point you will want to put new plants and seeds in the ground. The problem is that the soil is not always suitable for planting.

In fact, the soil can contain all kinds of insects and pathogens that can negatively affect plant growth. You may think that soil is dirty, but in reality, it’s best for your plants to use clean soil.

So in this article, you’ll discover can you sterilize soil with boiling water. Let’s start.

Why sterilize soil?

Soil needs good microorganisms. Bacteria and fungi produce nutrients and make them more accessible to plants. However, in some cases, it is better to sterilize the substrate – to kill the life in it!

Let’s look at some examples.

  • The soil becomes contaminated with disease-causing parasites and pathogens. If a diseased plant has been planted in a pot, it is very likely that the soil in the pot is contaminated.
  • As mentioned earlier, it is best to sterilize all potting soil used. Fungus gnats are most comfortable in moist soil and can wreak havoc on new plants.
  • Also, if you buy potting soil from an unreliable supplier, disinfect it as a precaution.
  • Seedlings are susceptible to fungal, bacterial and invertebrate infections, and the most common cause of seedling death is infestation by powdery mildew gnats.

For this reason, there are a number of pesticides, herbicides, and biocides that can be used to disinfect the soil.

However, all of these chemicals are potentially harmful to the environment and health, and most of them cannot be used in organic gardening.

Therefore, conscientious gardeners are always on the lookout for clean, natural, environmentally friendly, and harmless sterilization methods.

Can heat be used to sterilize floors?

As with other applications, heat can be used to sanitize a limited amount of soil.

Commonly recommended methods include boiling pot material or heating in a microwave oven.

However, some people do not have a microwave oven. Others do not want to put soil in the same oven that is used to prepare food. Also, boiling the soil gives it a strange smell.

Photo by Tom Fisk from Pexels

Can you sterilize soil with boiling water?

Some argue that even the hottest water (100°C) is not hot enough to sterilize the soil. Moreover, the water cools further when poured on the floor.

So hot water solves the problem for all groups of small animals. It is especially effective for insects and invertebrates.

Mosquitoes, like mites, cannot fight back once they come in contact with hot water or steam.

No wonder so many gardeners have had success with this method over the years.

However, it is necessary to take time for the hot water to work its magic.

It is not enough to pour boiling water on the plants to get the effect, you need to allow enough time.

How to sterilize soil with boiling water

So let’s get to work.

Here are two methods for disinfecting soil with boiling water.

1. Steaming the soil on the stove

Steaming on a stove helps keep the temperature constant throughout the process.

The general method is described below.

  • Prepare a large pot (buy an old or cheap used pot from your kitchen).
  • Put the substrate in it and fill it with water. The water should be high enough to float slightly above the bottom.
  • Bring the water to a boil. It doesn’t need bubbles. A large amount of steam is also a sign that the temperature is high enough.
  • Let it sit for at least 30 minutes.
  • When the soil has cooled completely (preferably the next day), you can work or improve it with a slow-release fertilizer or compost.

If you have a summer kitchen, you can do this conveniently outside, or you can buy and use a cheap hotplate.

2. Pour hot water over the floor

It is not necessary to constantly boil or actively steam the soil if adequate insulation is provided.

  • Some people use plastic buckets or boxes, but I would refrain from doing so as they do not provide adequate insulation and the plastic can release a number of harmful chemicals into the soil when exposed to heat.
  • Fill the bucket with soil.
  • Bring the water to a boil on the fire. Make sure you have enough. Many substrates can absorb large amounts of water.
  • Pour the boiling water over the soil and mix. The soil should be completely saturated and moist.
  • It is best to pour the soil in and soak it with boiling water beforehand.
  • Cover the soil with aluminum foil or a metal lid and let it sit for at least 30 minutes.

Are there any other sterilization methods?

If disinfection by boiling is too inconvenient, there are other methods of disinfection. Here are some of them.

1 – Use of steam

Like boiling water, this is another effective and easy method of floor disinfection. Simply fill a pot with water and place the soil to be disinfected in layers on a grid. Then simply close the lid and bring it to a boil.

Once the water boils, let the steam escape through a small opening and let the water boil for 30 minutes. This will kill enough pests that are mixed with the soil.

2 – Use of the oven

Another easy way to sterilize soil is to use an oven. Simply prepare an oven-proof container and fill it with about 15 cm of soil. Cover this layer of soil with aluminum foil and place it in the oven at 180-200°F.

The only problem with this method is that overheating the soil can create toxins that are not ideal for planting. To avoid this, use a thermometer that you stick into the soil.

Once the temperature reaches 180°F, turn off the oven and remove the soil. Keep it covered with aluminum foil until you are ready to use it.

3 – Using a microwave oven

Likewise, a microwave oven can be used to sterilize the soil. In this case, the soil must be kept moist.

Simply place the soil in a microwaveable container with a lid. It is not necessary to use aluminum foil for the soil, but be sure to use a lid with ventilation holes to allow steam to escape. Heat over high heat for 90 seconds per 2 pounds of soil.

When everything is ready, you can remove it and cover the vent with tape until you are ready to use the soil for planting.


Igra, J. (2020, October 17). How to Sterilize Potting Soil? – 6 Great Methods. Igra World.

P. (2021, August 19). How to Sterilize Soil at Home: Learn about the 8 Best Time-Tested Ways. Grow Plants.

Samurovic, K. (2022, January 17). How to Sterilize Soil With Boiling Water! Outdoor Happens Homestead.

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