How to Sterilize Coco Coir

If you plan to reuse your growing medium over multiple crop cycles, it’s important to sterilize it first to help prevent the possibility of spreading disease. This sterilization process can benefit a variety of substrates, including coco coir. This natural byproduct of the coconut industry has become a popular growing medium, particularly for hydroponics systems. Read on to learn how to sterilize coco coir.

Why Sterilize Coco Coir?

Coco coir is an all-natural, environmentally friendly material you can use repeatedly in your garden. Between uses, however, you should sterilize it to kill off any viruses, fungi, or bacteria that have developed and could affect new seedlings’ survival. The moisture and warmth that encourage germination also provide the perfect breeding ground for harmful microorganisms. The two common sterilization methods gardeners use are chemical and heat.

Chemical Sterilization

Gardeners can use a variety of chemicals to sterilize coco coir between growing seasons. These include:

• Bleach. After removing the previous batch of plants, place your coco coir in a large bucket. Submerge it in a mixture of 4 teaspoons of bleach for every gallon of water for at least a half hour. Stir the coir around to make sure all of it gets exposed to the bleach. Then drain and rinse the coir with water until you can no longer smell bleach.
• Hydrogen peroxide. Similar to the bleach method, you can soak coir in a 35 percent hydrogen peroxide and water mixture (2 mL per liter of water) for at least four hours. Then rinse thoroughly and reuse.
• Quaternary ammonium salts. Cleaners and disinfectants that contain these salts can also sanitize coco coir when used per label directions.

Heat Sterilization

Heat sterilization is a more eco-friendly option and occurs through pasteurization. Heat sources include:

• Oven. You can sterilize growing mediums such as coco coir by placing them in an oven heated to 180 degrees F for 30 minutes. This effectively kills pathogen eggs and larvae as well as harmful fungi.
• Microwave. You can heat-sterilize small amounts of moistened coir in the microwave for three to five minutes.
• Sun. On a hot, sunny day, you can place moistened coir beneath a clear tarp material. It must maintain a temperature of 150 degrees F for at least 30 minutes to kill pathogens.

Sterilization Considerations

When deciding how to sterilize coco coir, keep the following in mind: Bleach and other chemicals can be harmful both to people who inhale or come in contact with it as well as to the environment. Make sure there’s good airflow where you’re sanitizing and that you dispose of the soak water properly and immediately. When using heat sterilization, know that this method can also kill the good microorganisms coco coir is known to carry. It can produce a bad odor, as well.

To ensure recycled coco coir remains viable and porous, you might need to add an enzyme product, another growth medium, or perlite to the existing material.

Consider these methods when decided how to sterilize coco coir. Reusing this growing material in your hydroponics system can help save money in the long run.