How to Sterilize Potting Soil

How to Sterilize Potting Soil

Keep Your Houseplants Healthy

Houseplants are an attractive and healthful addition to any home, and quite often, shortly after purchasing a new houseplant, it becomes necessary to transplant it into a new pot. Houseplants sold in stores are sometimes already considerably root bound, and once the roots have filled the pot it's time to provide a little more legroom. Besides a new container a couple of inches larger, you'll need potting soil before beginning the transplanting process.

Potting medium sold in stores provides the right combination of nutrients and rich organic material to help your houseplants thrive, but potting soil sometimes comes with more than plant lovers bargain for. Soil-borne fungi and insects are sometimes included at no extra charge, but these are freebies you really don't want to bring home.

Just because potting medium is labeled as sterilized doesn't mean it won't contain something extra. Bagged potting soil might still contain harmful fungi, soil-borne diseases, or destructive insects, and it's a good idea to sterilize potting soil before using to ensure it's truly sterile. The following information provides step-by-step instructions on how to sterilize potting soil. When you sterilize your planting medium, you ensure the health and well being of your houseplants, and beginning with healthy soil is the first step in maintaining vigorous abundant houseplants.

When potting soil is heated, it produces a strong unpleasant odor. Be sure to provide adequate ventilation by opening a nearby window and turning on an exhaust fan. Keep children and pets out of the room.

In addition, the temperature of the medium you sterilize should not exceed 180 degree Fahrenheit during the heating process. Higher temperatures can produce substances that are toxic to plants. If the temperature exceeds 180 degrees Fahrenheit, discard the soil appropriately, and start over.

Easy Oven Method
To sterilize potting medium in the oven you'll need a large oven-safe roasting bag, a large baking sheet or roasting pan, a meat thermometer, 5 cups of fertile potting soil, and one cup of water. You'll also need a potholder or oven mitt, and a cooling rack.

Begin to sterilize the soil by placing approximately 5 cups of loose houseplant medium in a large oven-safe roasting bag, and thoroughly mix in about 1 cup of water. Place the bag on a baking sheet or in a roasting pan, and loosely affix the opening so steam can escape. Stick a meat thermometer through the bag, and into the dirt. Set the oven to a very low temperature, and turn it down when the thermometer reaches 170 degrees Fahrenheit so it doesn't exceed 180 degrees Fahrenheit. Try to keep the temperature constant for about 30 minutes to ensure safe and adequate sterilization. After you sterilize the planting medium, carefully open the bag after 30 minutes of continual 170-degree temperatures, and allow it to cool to room temperature before using.

Important Note
Once you sterilize the soil, you must sterilize the pots and saucers before using to ensure the soil remains sterile. Soil-borne diseases, fungi, and insects can live in small amounts of soil and debris remaining in previously used and inadequately cleaned pots and saucers.