What’s really in pre-packaged soil mixes?

You used to be able to buy a house, walk out the back door, and, if you were so inclined, dig a little vegetable patch. Nothing complicated. Just plant some carrots and beans or maybe stake a row of tomatoes. But things are so much more complicated now.

The Toronto Star ran an expose last fall on toxic dirt being dumped in Ontario’s prime farmland. With lax rules about soil contamination and no tracking system, dirty dirt can be hauled from downtown condo building sites or the construction zones for this year’s Pan Am games, for instance, to the countryside where your next meal may be coming from.

New home development properties can have yards filled with soil that’s equally questionable. This can be a real problem if you want to grow food to eat. Many resources are now suggesting that raised beds are a safer option as well as being practical. A raised bed can offer improved drainage, can warm up the soil faster so you can get to sowing sooner and, hey, it’s easier on your back.

So what do you fill those raised beds with? Or any plant container for that matter? If you don’t have your own composter or access to plenty of soil you know to be safe, you’ll have to rely on commercially available soil. When I ponder what to buy at the local garden centre, I start coming up with more questions than answers. So here’s what I’ve decided to do:

For growing flowers in containers: I’m going to stick with packaged potting mix–the sterilized, soilless kind. Yes, it’s got all kinds of stuff in it which may or may not be good depending on where you sit on the subject of organic gardening. But, I’m not eating any of my flowers and, since this “soil” will be isolated in its own pot, I’m OK with it.

For growing edibles in containers: I don’t want to grow what I’m going to eat in soil that may contain chemicals, including fertilizers, herbicides, fungicides, and pesticides. But, I’m going to ignore any vegetable soil mix that says it’s “organic”. There are lots of loopholes that allow companies to call their product organic when these products aren’t really organic in the good-for-you organic way. Instead, I’m going to look for one of two logos: The Canada Organic symbol which can only be used on certified organic products and the OMRI Canada symbol. The Organic Materials Review Institute website has a handy products search tool for finding potting soil brands, among other things, that comply to the Canada Organic Regime standards.

What about fertilizers? Last year, I wrote a post on the pros and cons of buying commercially available, packaged manure. I’d been asked whether or not manure (the kind you get at any big box garden centre) was “organic” or not. I started looking at the ingredients lists on several branded products and started to realize that so-called natural fertilizers may not be all that natural. The upshot is that if a product isn’t labelled as certified organic, you may be buying more than you bargained for.

And, speaking of safety on a different level, if you’ve got a smoker in the house and you’ve still got some pots from last year filled with dead plants and old potting soil mix, warn them not to stub out their cigs in the pots. Turns out potting soil can spontaneously combust if the conditions are right and can most definitely burst into flames from a cigarette.