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should I sterilize potting soil before sale?  RSS feed

 
Gilbert Fritz
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Location: Denver, CO
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I'm considering getting into the potting mix business on a small scale. Does potting mix need to be sterilized before sale?

I would think not; it seems that there would be so many chances to get reinfected before sale in any case. And most organisms are helpful, not harmful. In fact, I've heard some say that sterile soil is simply a gimmick, aside from killing weed seeds.

But on the other hand I would be worried about lots of refunds for damping off losses if my soil was not sterilized.
 
James Freyr
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I'm inclined to believe the reason companies currently sterilize potting mixes is to kill weed seeds, not pathogens. I've purchased dump truck loads of topsoil before and it is amazing the what shows up after a rain that wasn't currently growing before the topsoil was delivered. The last truck load of topsoil I got was full of crimson clover and vetch. I wouldn't worry about sterilizing potting mix to kill nasty microbes because as soon as the consumer opens the bag, the mix will be inoculated with whatever airborne spores are around, both good and bad, not to mention as soon as the potting mix came out of the sterilizing machine, it will pick up airborne spores on its way into the bag. I would sterilize the potting mix to kill weed seeds, since consumers are used to whatever they plant being the only thing that grows, at least at the very beginning, with individual weeds showing up one by one from the wind blown seeds or bird droppings.
 
Marco Banks
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The reason you put compost around your plants and into you potting soil is to do the exact opposite of sterilize.  You WANT as much bacteria and fungi possible in your soil.  Otherwise, it's not soil -- it's dirt.  Soil is a living bio-intensive substance.  If you get a few weed seeds, so be it, but don't kill all that wonderful soil life.

Consider hot composting as a way of dealing with weed seeds.
 
Judith Browning
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Gilbert Fritz wrote:I'm considering getting into the potting mix business on a small scale. Does potting mix need to be sterilized before sale?

I would think not; it seems that there would be so many chances to get reinfected before sale in any case. And most organisms are helpful, not harmful. In fact, I've heard some say that sterile soil is simply a gimmick, aside from killing weed seeds.

But on the other hand I would be worried about lots of refunds for damping off losses if my soil was not sterilized.


If I were buying potting soil, I would want to know what ingredients were in it and that it was not sterilized.  I think you could possibly turn that into a selling point...let folks know that it's 'alive'.  

If I saw potting soil that was made from quality ingredients and not sterilized I would probably buy some.  All that is available locally here is ground wood with some nasty fertilizer incorporated so I'm always scrounging up things to make my own.

I've had no problem with damping off since I started sprinkling cinnamon on the surface of my flats after seeding them so 'unsterilized' is not an issue for me.

I think an excess of weed seeds might be more of an issue, especially if they were things like bermuda grass or other unwanteds.  I'm always bringing in new 'weeds' though every time I go to a plant exchange...some have been very interesting.....
 
Harry Soloman
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Indoor growers are the ones who  tend to sterilize and then add their own microbes as they are worried about bugs.  Many indoor growers are growing high value crops and may be quasi legal in some states.  They are worried about bugs like thrips, spider mites, gnats, aphids and such.
If selling to these types offer nematodes and BTI.  Even if you start with pristine soils not infected with bugs by the time transportation and storage until the point of sale takes place it is likely to get infected.  Unless you was  going to specialize in selling to this group, I would not invest the time, energies and costs to cater to this group.  Many will make their own indoor soils and add their own microbes due to insect concerns.

Regular outdoor gardeners generally do not care as outdoor nature is all part of the cycle as long as not truly infested.  I actually want a bit of stress on my plants, notice I said a bit and not infested!  We can plant predator bug friendly plants to attract friendly bugs and use other techniques that assist with controls of insects indoor people cant.

Best of luck in your endeavor and I wish you great success!  I hope to see more permies selling quality soils and such as this is how in part the world can heal but mostly humanity will always go where easy and cheap meet regardless best practice for many reasons, some valid some not so much.
 
Joylynn Hardesty
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Judith Browning wrote:
I've had no problem with damping off since I started sprinkling cinnamon on the surface of my flats after seeding them so 'unsterilized' is not an issue for me.



Do you remember what action the cinnamon does that helps prevent dampening off? I start my tomato and pepper seeds inside. With the sterile soiless mixture the problem is much reduced. But it just seams wrong to not use soil...
 
Judith Browning
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Joylynn Hardesty wrote:
Judith Browning wrote:
I've had no problem with damping off since I started sprinkling cinnamon on the surface of my flats after seeding them so 'unsterilized' is not an issue for me.



Do you remember what action the cinnamon does that helps prevent dampening off? I start my tomato and pepper seeds inside. With the sterile soiless mixture the problem is much reduced. But it just seams wrong to not use soil...


I'm not sure where I read originally but 'anti fungal' properties are what do the trick.

Using Cinnamon to Prevent and Stop 'Damping Off' Diseases on Seedlings. Cinnamon has some anti-fungal qualities and it smells great as a bonus. 'Damping Off' diseases are the bane of seedlings. It is the gray white furry fungus that forms on the stems of your seedling right where they meet the starting mix.

http://therustedgarden.blogspot.com/2013/02/using-cinnamon-on-seedlings-stop.html

I don't know if this is the best site for info but I ran across it first.  I keep a salt shaker full of cinnamon handy when I'm starting flats...at first I wasn't sure if it wasn't just coincidence.  After a few years I'm pretty sure it works.  We buy cinnamon in bulk and sometimes use the expensive best quality stuff and sometimes lesser quality...it doesn't seem to matter which I use on the potting mix, which is different every year, sometimes garden soil with more sand and compost, sometimes coir, compost and perlite, sometimes old potting soil, compost, sand and a bit of garden soil....

I'm one of those who tends to overwater rather than underwater...making potting mix that is too moist to where I would have to turn on the fans and in the past would lose seedlings to damping off. 
 
Gilbert Fritz
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Thanks for the advice! That is as I thought.

I'll start a dedicated thread about my potting soil experiments once I get a little further. I'm hoping to have a product ready for sale by next spring.
 
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