Daylilies forum: Microwaving potting mix to sterilize it

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Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
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beckygardener
Dec 22, 2015 9:18 AM CST
I need some advice. I have a bag of what I consider my favorite and best potting mix. I always use it for sowing seeds. It's a bit more expensive than other potting mixes. I have a bag that has been opened but was kept closed in my garage for over month. I want to use this bag for seed starting but am worried about gnats especially gnat larvae that can destroy sprouting seeds.

I have an old microwave that we were going to throw out but forgot to. It is also in my garage. It still works. I had read about sterilizing potting mix in a microwave. So I would like to try that. What I need advice on is HOW to sterilize potting mix in a microwave oven.

What do you put the potting mix in to cook it in the microwave?

How long do you cook the potting mix in the microwave to kill any bacteria, fungus, or bugs? I want the mix sterilized for seed starting.

I have perlite in this potting mix. Would that cause a problem when heating the mix in the microwave? It wouldn't explode or anything, right?
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
[Last edited by beckygardener - Dec 22, 2015 9:31 AM (+)]
Give a thumbs up | Quote | Post #1013486 (1)
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
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beckygardener
Dec 22, 2015 9:23 AM CST
Do these 2 instructionals seem accurate?

http://homeguides.sfgate.com/microwave-potting-soil-48342.ht...

http://www.momsbudget.com/containergardening/sterilizemicrow...

I am still worried about how the perlite reacts to extreme heat. Anyone have any experience doing this?
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
[Last edited by beckygardener - Dec 22, 2015 9:27 AM (+)]
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Name: James
South Bend, IN (Zone 5b)
Hostas Enjoys or suffers cold winters Birds Seed Starter Annuals Region: Indiana
Region: United States of America Dog Lover Daylilies Container Gardener Plant and/or Seed Trader
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JWWC
Dec 22, 2015 10:07 AM CST
Hmmm... I don't know about the perlite - perhaps someone else can speak to that. I have microwaved soil-less mix without it before and really what you're going for is heat. I wet the mix (not sopping wet but damp) and put it in a pyrex bowl (easy enough to clean afterwards) and into the microwave. I zapped it on full power for 5 minutes, mixed it around, then 5 more minutes. It will be HOT HOT HOT so be careful.

Another option is to water with dilute hydrogen peroxide but that was unsuccessful for me.

The other, likely easier option, is to top with something like gnatnix or water with some gnatrol. I have done neither of these but perhaps one of these two ( @Ahead @Nysbadmk8 ) can answer any questions you may have about that.
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
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beckygardener
Dec 22, 2015 10:23 AM CST
James - I purchased some 1.oz (28g) Gnatrol OMRI selective biological larvicide for Fungus gnat control this year but have not used it because I didn't know how it would affect germinating seeds. Plus there was no label on the container and I can't find the instructions that came with it on how to measure and use it. But I have some. I just didn't want to kill my very young seedlings with Gnatrol.
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
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sooby
Dec 22, 2015 10:51 AM CST
Becky, here's an article by North Dakota university extension that has a paragraph of instructions for pasteurizing in a microwave:

https://www.ag.ndsu.edu/pubs/plantsci/landscap/pp744.pdf

You could test the mix for fungus gnat larvae by placing some sliced potato on it and checking under the slices in a day or so.

The label for Gnatrol should be easy to find on Google, just type in: Gnatrol msds label

I wouldn't be too concerned about perlite although I don't know for sure if it would be a problem in the microwave, since it is heated volcanic material in the first place. I would make sure it really is perlite and not polystyrene though.
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
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beckygardener
Dec 22, 2015 11:03 AM CST
Thanks, Sue! I will check out that link. I also found my old email from the seller of the Gnatrol so sent an email asking for the instructions. Either way, I am sure I can get them. I just do not know how safe Gnatrol is with sprouting seeds? Anyone know?

Sue said, "I would make sure it really is perlite and not polystyrene though." Good point!
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
[Last edited by beckygardener - Dec 22, 2015 11:06 AM (+)]
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Name: Steve Todd
Illinois (Zone 5b)
Region: Illinois Plant and/or Seed Trader Daylilies Enjoys or suffers cold winters
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Ahead
Dec 22, 2015 12:17 PM CST
Why is it that my name is associated with gnats? I tip my hat to you.

Becky, I never nuke. I use gnatrol, and have for a million years. I like to keep things simple....for obvious reasons....lol. When I plant my seeds, I use a mixture of water and gnatrol for the first week or so after planting. It has worked very well for me.
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
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beckygardener
Dec 22, 2015 2:18 PM CST
Steve - Thanks!

Now to find the dosage amount and instructions on the use of the Gnatrol dry powder that I have.
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
Name: Steve Todd
Illinois (Zone 5b)
Region: Illinois Plant and/or Seed Trader Daylilies Enjoys or suffers cold winters
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Ahead
Dec 22, 2015 6:48 PM CST
Becky,

I buy new every year...seems to lose it's strength the second year.

Happy germination!
Name: Lisa Klette
Dayton, KY (Zone 6a)
Daylilies Garden Art Plant and/or Seed Trader Region: Kentucky Hostas Sempervivums
Dahlias Celebrating Gardening: 2015
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Lilydaydreamer
Dec 22, 2015 6:49 PM CST
Where do you buy it?
Love what you teach and teach what you love!
Name: Steve Todd
Illinois (Zone 5b)
Region: Illinois Plant and/or Seed Trader Daylilies Enjoys or suffers cold winters
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Ahead
Dec 22, 2015 7:09 PM CST
Amazon.
Name: Lisa Klette
Dayton, KY (Zone 6a)
Daylilies Garden Art Plant and/or Seed Trader Region: Kentucky Hostas Sempervivums
Dahlias Celebrating Gardening: 2015
Image
Lilydaydreamer
Dec 22, 2015 7:54 PM CST
Thanks

This seller?
http://www.amazon.com/Valent-Gnatrol-WDG/dp/B003E7BGTU/ref=s...
Love what you teach and teach what you love!
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
Image
beckygardener
Dec 22, 2015 8:33 PM CST
I bought mine from someone else on Amazon. I read that the powdered/granule form can last 2 years. Liquid form only lasts 1 year.

Steve - Do you use the liquid form or the powdered form?
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
Name: Steve Todd
Illinois (Zone 5b)
Region: Illinois Plant and/or Seed Trader Daylilies Enjoys or suffers cold winters
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Ahead
Dec 22, 2015 8:45 PM CST
I use the powder form.
[Last edited by Ahead - Dec 22, 2015 10:12 PM (+)]
Give a thumbs up | Quote | Post #1013896 (14)
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
Image
beckygardener
Dec 22, 2015 10:03 PM CST
Do you remember how to mix it? I haven't found the instructions and the seller has not replied to my email.
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
Name: Steve Todd
Illinois (Zone 5b)
Region: Illinois Plant and/or Seed Trader Daylilies Enjoys or suffers cold winters
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Ahead
Dec 22, 2015 10:17 PM CST
This is off an old jar. I never measure, but here's the label:


Thumb of 2015-12-23/Ahead/0fea21

You need to click the image to read it.
[Last edited by Ahead - Dec 22, 2015 10:18 PM (+)]
Give a thumbs up | Quote | Post #1013935 (16)
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
Image
beckygardener
Dec 22, 2015 10:21 PM CST
Steve - THANK YOU very much! That's exactly what I needed. Thumbs up Thumbs up Thumbs up
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden
Name: Steve Todd
Illinois (Zone 5b)
Region: Illinois Plant and/or Seed Trader Daylilies Enjoys or suffers cold winters
Image
Ahead
Dec 22, 2015 10:33 PM CST
No problem, Becky. Good luck!

Lisa, I couldn't tell you...but I never got it that cheap!

My newest bottle has an expiration date, and was for a larger quantity.
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
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sooby
Dec 23, 2015 5:40 AM CST
Becky, there's a specimen label for the WDG form here so that you can read the precautionary statements:

http://www.valent.com/Data/Labels/2012-GNT-0001%20Gnatrol%20...
[Last edited by sooby - Dec 23, 2015 5:43 AM (+)]
Give a thumbs up | Quote | Post #1014024 (19)
Name: Becky
Sebastian, Florida (Zone 10a)
Celebrating Gardening: 2015 Daylilies Hummingbirder Butterflies Seed Starter Container Gardener
Charter ATP Member I was one of the first 300 contributors to the plant database! Garden Ideas: Master Level Lover of wildlife (Black bear badge) Birds Ponds
Image
beckygardener
Dec 23, 2015 6:41 AM CST
Sue - Thank you for that link.

Yes, I figured it was toxic. I don't really want to use it, but was planning to use it as a back-up plan if sterilizing my potting mix didn't work.

I am still determined to sterilize the potting mix and will be doing it trial and error following the links in my second post above. I did dose the current seed cups with H2O2 & water twice when I planted the seeds in them and am hoping that may have helped to kill any gnat larvae. But I will try the gnatrol if I have a problem and mix it outdoors since I do have 4 pets. I am an organic gardener, so chemicals go totally against my gardening style.

The other problem that I have is the potting mix I love is sold at a nursery and stacked outside. The bags have air holes in them, so they may come with gnat larvae already in them. (And I suspect as much.) So I definitely need to figure out a way to sterilize the mix. I can't find this potting mix anywhere else locally. But .... it is such a good mix, that I am willing to try sterilizing it myself!

Thanks for everyone's help!
What lies behind us and what lies before us are tiny matters, compared to what lies within us.
Garden Rooms and Becky's Budget Garden

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