Soil harbours disease organisms, insects, insect eggs and weed seeds. These pests can kill young seedlings and compromise the health of mature plants grown in it. Most purchased soil comes sterilised, but garden soil, homemade compost and reused potting soil requires sterilisation to ensure its safety to your plants. Heat from steam kills diseases and pest and renders weed seeds unviable. Once cooled, the sterilised soil provides an optimum medium for growing seedlings and plants.
- Skill level:
- Moderately Easy
Things you need
- Pot with lid
Fill a large pot with water to a 1-inch depth. Set a rack in the pot that is tall enough to sit above the water.
Place moistened soil in a pan that is small enough to fit inside the pot. Fill the pan no more than 4 inches deep.
Smooth the soil surface with your hand. Cover the soil with a sheet of aluminium foil.
Set the pan on top of the rack in the pot. Fill multiple pans and stack them on top of each other, but don't stack pans higher than the walls of the pot.
Set the lid on the pot, leaving it cracked open slightly so steam can escape. Bring the water to a boil over medium-high heat.
Boil the water for 30 minutes. Check the water level in the pot every 5 to 10 minutes, and add additional hot water, if necessary, so the pot doesn't boil dry.
Turn off the stove burner after 30 minutes. Secure the lid closed and allow the soil inside the pot to cool to room temperature before using it.
Tips and warnings
- Store the sterilised soil in a clean, sealed container until you are ready to use it to keep the soil sterile.
- Sterilise only compost or soil. Mineral potting soil additives such as vermiculite and perlite may produce harmful gases when heated.
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