I posted this in the container gardening forum but have not gotten any response yet. This may be a better place for my question:
I'd like to plant some salad greens (and herbs) with my kids (both as an activity and as a way to encourage them to eat more greens), but I haven't done much because I don't know where/how to get soil that is chemical-free. Potting soils in bags? Water a pot of soil long enough to clean it? Put aside a pot of soil for it to 'naturally' mature?
It shouldn't be hard for you to find organic humus and organic compost in bags. Check with your local nurseries. You don't need a deep container for salad greens.
Another option for salad greens is to grow them in an inch or two of compost on top of a straw bale. You water the bale for a few weeks, then put some compost on top and sow the seeds. See the straw bale gardening threads in Vegetable Gardening.
I am actually mostly interested in "rehab" my own soil. Composting is new to me, but overtime I'll get the hang of it. What about old potting soil? It is soil after all. Is it possible to get rid of the chemicals by repeated watering? (but then the nutrients would be washed out as well, I suppose.)
The "lasagna" method of rehabbing soil is a good one. There are books about this at your local library, and threads on it in this forum. I'd also recommend "The Vegetable Gardener's Bible" for a practical organic approach.
Basically, I add grass clippings and shredded leaves from our yard to my garden soil, as well as chicken poo and litter from our hens. This feeds the soil and also improves its tilth, making it more fluffy, water-retaining, and wormy. My vegetables are happy.