How to Disinfect Seed Trays

Sometimes I have a hard time being flexible.

I’ve been like that for as long as I can remember… If we had something on the calendar growing up, it was gonna happen. No ifs, ands, or buts about it. And if it didn’t? Well, I pretty much had a meltdown.

I’ve grown out of the meltdown part (although my husband might try to argue that point…), but dang it– if I put something on the calendar, you can bet I’ll go to the ends of the earth to make sure it happens.

Let’s just say it’s a blessing and a curse.

ANYWAY.

This does tie into today’s post, I promise.

So I had “plant tomato and pepper seeds” written on my calendar for the ‘project of the day’ last Saturday. I cleaned up the kitchen after breakfast, got the kids occupied with a project, and headed to the basement to dig out my big box o’ seed stuff.

That’s when I discovered I had a grand total of 8 little coconut coir pellets left. And approximately 2 cups of potting soil. This was a problem.

Way to go, Jill. Way to go. 

A quick visit to Amazon got 200 of the little pellets (affiliate link) on their way to my house via USPS, but that wasn’t going to help me that day.

But I wasn’t about to abandon my seed operation. I was determined, y’all. It’s February. I haven’t touched a plant in months. I HAD to do something so I could pretend I was gardening. So I decided to give my seed trays and flats a good scrub and disinfecting, which is how this blog post was born. Poor planning for the win, I suppose.

Do You Really NEED to Disinfect Seed Trays?

Maybe. Probably not? I don’t know. 

How’s that for an answer?

Truth be told, I don’t always disinfect my seedling flats, pots, cups, or trays. If you’ve been following me for any length of time, you know I’m NOT a germaphobe, and I’m pretty laid back about such things. (I rarely even sterilize my chicken coop for new chicks— I believe in the power of good bacteria.)

However, if you’ve had issues with any sort of plant disease, fungi issues, or damping off (more on that below), I would definitely plan on cleaning and disinfecting your seed starting equipment before you start your seeds each year.

It’s cheap insurance to prevent big issues like damping off, which can be borderline devastating when you’re anxious to get your seeds rolling. (And Lord knows we are…)

What is Damping Off?

You plant the seed.

You water the seed.

The seed begins to emerge from the soil and you get all excited.

And then said seedling shrivels and DIES with no explanation.

That’s damping off. It’s so rude.

For the more technical-minded, damping off is a disease of seedlings caused most commonly by fungus or mold. Sometimes it affects just a handful of your seeds, while other times it can wipe out entire trays of fledgling plants.

Needless to say, you don’t want to be dealing with damping off, so it’s wise to take simple precautions to prevent it.

How to Prevent Damping Off in Seedlings:

• Don’t reuse dirty potting soil
• Keep your seedlings warm while they are sprouting (our basement is cold, so I keep a small heater in the room and run it on low heat)
• Water seeds or seedlings with lukewarm water, not ice cold
• Don’t crowd seedlings
• Provide seedlings with sufficient light (usually 12-16 hours of consistent light– oftentimes window light is not enough. I use fluorescent lights for my seed starting set up.)
• Clean and disinfect pots, flats, and trays before you use them to start seeds, which is what we’re talking about today.

How to Disinfect Seed Trays

Not surprisingly, the most common way people disinfect or sterilize seed starting equipment is with bleach. The Internet has such a fascination with bleach, but I can’t stand the stuff.

Thankfully, hydrogen peroxide comes to the rescue. Yup, just plain old, drugstore-strength, 3% hydrogen peroxide. Easily available, cheap, and much less stinky. Bingo.

Here’s how I disinfect my seed trays the natural way– no nasty bleach required:

Step One:

Shake out any residual soil from the seed trays and flats. You may need to soak everything in a bit of water if any soil is dried on and super crusty.

Step Two:

Scrub the trays and containers with warm, soapy water. I used a bit of my #1 favorite natural cleaning concentrate in the entire universe for this part, On Guard Cleaning Concentrate. This concentrate, by itself, will likely eliminate most of the issues that cause damping off, so I figure using it alongside hydrogen peroxide is the perfect one-two punch. If you don’t have any On Guard cleaner, you can use regular soap and water. (And then order some On Guard Cleaner. You’ll thank me later.)

Step Three:

Spray the trays, flats, cups, or whatever with a generous spritz of hydrogen peroxide, then let everything sit for 20 minutes.

Step Four:

Wipe with a clean, dry cloth, and you’re ready to plant! Pretty easy, eh? Disinfecting your seed equipment is a project you can easily complete in a morning or afternoon and it’s a simple way to eliminate one of the biggest causes of damping off.

Seed Tray Disinfecting Notes:

• I would recommend doing this project outside. It was stupidly cold and windy the day I did it, so I opted to wash in my laundry room tub. However, it’s a messy task that’d be better suited for a warm spring day where you can use a big plastic tub outside, or something along those lines–especially if you have a lot of trays. Also, leaving your seed trays to dry in the sun for a while is another way to kill off any bad stuff that may be lingering inside.
• What about vinegar? Yeah, I know– I was wondering the same thing. Using vinegar was my initial thought, but I’m not certain it has enough punch to kill off all the problematic microorganisms. And if I’m going to go to the trouble of disinfecting everything, I want to be sure the effort was worth my time, which is why I opted for hydrogen peroxide instead. If you do want to try vinegar, you could spray the rinsed flats and pots with a spritz of white vinegar, wipe, and then follow with another spritz of hydrogen peroxide.
• If you want to know all the details of our laundry room washtub sink, here’s a post with all the details.

Other Seed Starting Posts You’ll Love:

• Our DIY Seed Starting Set Up
• The Ultimate Seed Starting Guide
• How to Make Paper Pots
• DIY Soil Block Maker
• Where to Buy Heirloom Seeds
• How to Test Seeds for Viability

 

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