How to Sterilize Soil

Updated on April 28, 2019
seh1101 profile image

Sean has been in the industry of gardening and landscaping since 2006. He is also a certified arborist that tends to focus on plant health.

Why Sterilize Potting Soil?

Sterilizing potting soil is very important when sowing seeds, seedlings, and cuttings. Soil naturally contains pathogens, harmful bacteria, and fungi that can harm or kill susceptible plants. Insects and larvae may also be present, which can harm plants and become a nuisance. Store bought soil that claims to be sterile may be contaminated via bag punctures, old shelf life, mishandling, and other numerous reasons. Sterilizing potting soil is easy and very beneficial to plant health. Only a few household items are needed, and about 45 minutes of time to prepare and sterilize the soil.

Materials Needed

  • Oven
  • Large Roasting Pan/ Baking Sheet
  • Aluminum Foil
  • Meat Thermometer
  • Fertile Soil
  • Water
  • Mixing Spoon

Be Forewarned:

Sterilizing potting soil indoors will cause an unpleasant odor that is extremely earthy.

Some people can tolerate it, but others may be panicking to open the windows for fresh air. Open the windows and turn on a ceiling fan before sterilization begins. The odor will not linger very long if the indoor air is circulating with outdoor air.

Preparing Soil for Sterilization

Soil Consistency

The soil needs to be moist enough to compact into a ball, but should crumble when pressure is removed. This can be done by simply packing a ball of soil between the hands. Add a little water and mix until the consistency is met.

Placing Soil into Pan
Place the soil into a roasting pan or baking sheet. Evenly distribute the soil in the pan and break up any clumps. Do not fill to the edge of the pan, and keep depth under 4 inches deep. Cover the pan or sheet tightly with aluminum foil. The foil needs to be tight and secure to prevent moisture loss and burning of the soil. Poke a hole in the center of the foil that is large enough for a meat thermometer to fit through.

Sterilizing Soil

Beginning Sterilization
Place the tray into an oven and set the oven to a low temperature. The ideal temperature for sterilization is 180 degrees Fahrenheit. Temperatures over 180 degrees Fahrenheit may cause burning. Burning the soil will chemically change the composition of the soil. Soil that is burned or overheated will harm plants.

Baking Duration
The soil needs to remain in the oven for 30 minutes, while the temperature needs to remain closely around 180 degrees Fahrenheit. Monitor the thermometer and adjust the oven temperature as needed. Paying close attention to temperature fluctuation is a must.

Cooling & Using Soil

Cool Down
After baking for 30 minutes, remove soil from the oven and let stand until the soil reaches room temperature. Carefully lift a corner of foil to allow heat to escape. The escaping steam will be very hot and can burn skin.

The soil can be removed from the pan and used once it has reached room temperature. Sow seeds no deeper than 4 times the diameter of the seed. Water the sterilized soil with a mister to avoid flooding the soil. Seeds sown into a container should be covered with plastic wrap and placed in a cool room. Avoid direct sunlight until germination. Gradually introduce light over a several day period and remove the plastic wrap once germination begins.

Important Tip:

Containers need to be sterilized before the newly sterilized potting soil can be added. Soil-borne diseases, fungi, and insects can live in small amounts of soil and debris remaining in previously used and uncleaned containers.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

Questions & Answers

  • Can I sterilize the soil for my houseplants in the same way you describe in your article?

    Yes, you can, but it may be easier to purchase a bag of sterilized soil if your plant's pot isn't too big.


    0 of 8192 characters used
    Post Comment
    • profile image


      9 months ago

      There's a simpler way to sterilize soil. There's an old boy scout gag played on younger scouts that illustrates a principle of physics. Place a paper cup of water or coffee directly in the camp fire and ask the novitiate how long before the cup burns. The correct answer of course is that the cup will not burn until the liquid is all evaporated. The liquid keeps the cup from exceeding 212 degrees. This principle is applicable to sterilizing soil in the oven. First, you don't need oven safe containers. I sterilize soil right in the plastic flower pots I get from the nursery. Second, it can't be too hot in the oven because the moist soil can't get over 212. I can sterilize eight one gallon pots in 45 minutes at 400 degrees. Take them out at 180 to 185 degrees. It takes over thirty minutes for them to cool to 160. Just like your turkey at tgiving. No need for foil wrap either. The top soil can dry out and thus get too hot. So put a wet paper towel or a bit of a rag on top of each pot to keep the surface hydrated.

    • profile image

      Richard Michael Bobick 

      16 months ago

      ALWAYS sterize soil regardless of what you are using it for. I have yet to open a bag of potting mix, planter soil, etc. regardless of brand that did not have gnats or other insects alive and well within.

    • sofs profile image


      8 years ago

      I have never heard about soil sterilization. Now that I know.. I will be trying this. I am glad you added those words of caution. Useful information. have a great day!

    • denisemai profile image

      Denise Mai 

      8 years ago from Idaho

      Oh, dear. I'm afraid I have two black thumbs. I also never knew about sterilizing soil. My lack of knowledge is most likely what's causing my plant growing to fail. Great, informative hub!

    • Brainy Bunny profile image

      Brainy Bunny 

      8 years ago from Lehigh Valley, Pennsylvania

      I don't know the first thing about gardening, so it never occurred to me that you would have to (or even could!) sterilize dirt. Very interesting!

    • chrissieklinger profile image


      8 years ago from Pennsylvania

      I started growing vegetables a few years ago and this is very helpful information that I never knew about. Thanks for an easy to follow guide. I can't wait to try this!

    • seh1101 profile imageAUTHOR

      Sean Hemmer 

      8 years ago from Wisconsin, USA

      Janis - Honestly, I usually don't sterilize bagged potting soil, but I know some who have gone through the work to make sure it is sterile (usually for specialty plants/crops). I generally sterilize when I don't know the source of the soil, such as a municipal mulch/dirt pile. Anything and everything gets dumped into municipal soil piles.

    • Janis Goad profile image

      Janis Goad 

      8 years ago

      When do you start potting in Tuscany, Good Lady? We are just getting started in Kamloops, and the soil won't be warm enough to plant out until the end of May. There is still snow in the high areas.

    • GoodLady profile image

      Penelope Hart 

      8 years ago from Rome, Italy

      Looks good and we will try it next year! Too late for now. All our potting has been done for the next season. Oh, except for an area we call the hospital where plants that look as though thy are on their last legs get put....and they grow. Perhaps we need to sterilize that soil to make sure they really will be OK now.


    • Janis Goad profile image

      Janis Goad 

      8 years ago

      Do you sterilize potting soil even when you buy "sterile mix" from the garden store? I never worried about it before.

    • Sage in a Cage profile image

      Sage in a Cage 

      8 years ago

      Interesting hub. I'm just starting to put some seeds down this week so it was really helpful.

    • angela_michelle profile image

      Angela Michelle Schultz 

      8 years ago from United States

      I actually had never heard of steralizing potting soil. It makes sense, but it had never occurred to me. Thanks for the great information.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)