Sterilization formulas

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Well-Known Member
May 21, 2007
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I am looking for any sterilization formulas for growing medias (i.e. Hydroton, lecca, pumice, Aliflor, or Primeagra). I'm new to using it for s/h and unsure whether just soaking with Physan 20 is enough or if you need to bake it for an extended period after it dries from the soaking. Any personal sterilzation rituals would be appreciated. I'm mostly using Hydroton and pumice and I have a small amount of Primeagra.
I would just soak it in a solution of chlorox.
Heating to a couple hundred degrees for a half hour will work also.
I think soaking in Physan is overkill for a number of reasons.
I really try to avoid using a lot of chemicals and none are needed if you heat sterilize. I used to boil the leca and then tried baking/broiling it, but honestly they both stunk up the house so much...and I got tired of hearing the Hubby complain about it. I wound up putting it off until he was out of the house and it was a real pain.

So, now I BBQ it! Yes, it sounds funny but works great. I've got a pretty fancy grill with thermometer and I put the leca in old pie plates etc. and BBQ at 500 degrees for about an hour. That's probably overkill for virus etc. but I like the particulate matter to turn to dust as it much easier to wash out later. I then put the BBQ'ed leca in a colander and rinse all the junk away. Rinse, rinse, rinse until there's no more dust or anything catching in the colandar holes. Then it goes in the sterilized bucket for future usage. The good thing is no odors inside and no mess to clean up.
Candice, I agree with you on the smell of boiling it. The last time I used only the soaking in Clorox, following Rays formula. Sure smells better, but I hope it is going to do as well as boiling. How will I know for sure????
I used to bake mine in the oven at 500 degrees for 30 minutes. That will kill just about anything.
trust me ....... I'm a scientist :)
You don't need 500 degrees but what's a little more burnt fuel anyway.

Yeah, that's what I thought:> I've actually BBQ it for less time, 30-40 mins. and I don't like that not everything has been burnt up. There was still some left over roots etc. About an hour for me, makes sure it's all dust.

Hey, I've got two kilns in the garage I could fire up to 1500 degrees! J/K! But, I've thought of using them when the BBQ was full:>
Hmmmm, interesting idea, Candace.
I have a TON of this to do and I usually boil it. I still think it's the easiest way, but I cannot do more than 12 quarts at a time. I use a large pot with a built in colander that works great but it's a chore hauling it up and down the stairs.

Maybe I will try some grilling this weekend.
Good ideas everyone.....thanks for sharing. So the next time your eating BBQ at Candace's and you think you've bitten into a piece of bone..chances are it's just some old growing media. Just teez'n Candace.:wink:
If I remember correctly once the media temperature has reached 180 degrees it should be kept at that temperature for 30 minutes. At that point most or all plant pathogens have been neutralized. At least that is what we used to do when we steam sterilized soil for snapdragon seedlings.

Over heating "soil" can damage the soil structure and make it bad for plants. This is what happens to tropical soils when the forest is cut down. But since we are talking about leca and other non soil media types high heat should not have any negative effect.

Candace you could make your own leca with your kilns. :poke:
I do have a bunch of clay sitting out in the garage... I've made some hanging terracotta mounts in the past. Donated them, gave them away etc. all very rustic as I'm not a potter. I haven't used my kilns in at least a year. I've got one large on and one small one. I threaten my husband that they'll never find the body and he knows exactly what I mean.:evil:

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