How to Sanitize Seed Starting Supplies

For the best chance of success when starting seeds indoors or in a greenhouse, it’s crucial to begin with clean and sanitized supplies. Young seedlings are vulnerable to fungal and bacterial diseases. Clean trays and containers mean less chance of seedlings dying or “damping off”. Learn how to sanitize seed-starting supplies with these simple steps.

Follow these simple steps for cleaning and sanitizing your seed-starting supplies: 

1. Gather needed supplies

You may already have everything you need to sanitize your seed starting supplies. It’s easiest to work outside.

You’ll need an area (size depends on the number of seed-starting supplies) to spread out and spray off the supplies. 

A large tub (or two) for washing, rinsing, and submerging seed trays and containers.

• Mild detergent
• Brush or sponge (I like using these bottle brushes to clean the seed starting containers)
• Vinegar
• Spray bottle(s)
• Hydrogen peroxide (3% or 12%, depending on the method used)

2. Remove debris and wash seed trays and supplies

Seed trays, domes, and containers are dirty and need some elbow grease to get cleaned up and ready for the next season.

Fill the large tub with water and add a mild detergent. 

Submerge the containers and use the sponge or brush to scrub and dislodge all the dirt and debris. (Rinsing alone usually isn’t enough to remove the dirt and soil.)

Lay out trays and containers, and rinse off with a spray of water. 

Repeat with remaining seed trays and supplies. 

3. Spray trays off with a diluted vinegar solution

Once the trays are clean, spraying them with a vinegar solution can help remove water spots.

Mix equal parts vinegar and water in a spray bottle. 

Spray off all surfaces with the vinegar solution.

Allow the solution to stay on for ten minutes, then rinse.

4. Use hydrogen peroxide to finish sanitizing your seed starting supplies

There are two methods for completing this step; choose the one that best suits your situation.

To quickly sanitize seed starting supplies:

• Put hydrogen peroxide (3%) in a spray bottle.
• Spray all surfaces of the trays and containers with hydrogen peroxide.
• Let it sit for 10 minutes, then rinse thoroughly.
• Air dry.

If damping off and fungal diseases have been an issue in the past, you may want to use this method, which provides the highest level of sanitation: 

• Fill the tub with 4 parts water and 1 part food grade (12%) hydrogen peroxide.
• Submerge and soak trays for 10 minutes.
• Remove and rinse.
• Air dry.

Note: 12% hydrogen peroxide can cause skin irritation. Wear chemical-resistant rubber gloves when using. 

Read this blog post for more information about starting seeds indoors.

If you live in the low desert of Arizona, this post shares when to start seeds indoors for transplanting outside.

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