Smart boy!
I don't really know what the safe method is so don't go by what I say. But, psssssssst! Lemme' tell ya' what I'd be inclined to do - that is, if I insisted on getting them potted without buying new soil . . .
Sift the soil as much as possible - then spread it on flat pans and bake it in the oven to sterilize it.
I've heard of that - it smells awful, they say, but I guess you could always set an open pack of baking soda in the oven afterwards.
Now don't go doin'it - wait till the others tell you what to do. Maybe I'm right - but then again, maybe I'm wrong.
I'm with ya' all the way. Save money and product wherever possible.
Some
plants do well with a few stones in it and some
plants don't require much room for a root . . . so you put loose stones in pots before you add your (pre-treated) soil. Wash the stones first so you're not spreading bugs.
Then spray the foliage with a very light solution of detergent (baby shampoo maybe).
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