Sterilizing water and soil substrates

There are many times in a gardener’s life when you may want to be able to use sterile soil and/or water, such as for hydroponic growing or with disease-sensitive cutting propagation. If you have a microwave or oven, you can easily do this at home with whatever soil substrate or water you may have. You can use these methods to sterilize fertilizer like compost or manure also. Getting the material to a microorganism-destroying 270° F for a certain minimum period of time is the general goal. A thermometer may be used to ensure temperature throughout but is not really necessary. Be sure to let water, fertilizer, or soil cool before using it with your plants.

Water: Bring water to a rolling boil and boil for at least 60 seconds to sterilize

Soil:

1. Soil is most easily sterilized in the oven:
   1. Place soil no more than four inches deep in oven-safe containers
   2. Bake in oven at 275°F for at least 30 minutes after soil reaches temp, I usually just throw my soil in a cold oven then bake at 275°F for 60-90 minutes just to be sure
2. Microwave oven:
   1. Moisten soil and place in microwave-safe containers, preferably no more than four inches deep and a couple pounds of soil substrate at a time
   2. Microwave on high for two minutes for most amounts, 60-90s for tiny amounts and up to three minutes if you have 32oz or more

And now you know how to sterilize your gardening water, soil, and fertilizers. No science degree needed! Happy growing my fellow gardening fiends!