I think 'potting soil' is just a generic term for any sort of growing substrate that is black and can be put in a pot...upon further reflection, it might imply that the mixture is topsoil-based instead of based on peat or some other 'loam'

But thats just what I think. :)

The most important thing is "does it grow good plants without burning them?" (organics can burn a plant just as chemical fertilizers can)

Potting 'soil' has dirt - soil - as it's base. How much dirt it contains varies from brand to brand.

Potting mix does not contain dirt - it is a blend of peat or the equivalent and other components such as vermiculite or perlite and seldom contains ANY soil per se.

Potting mix is best for containers as it is lighter, doesn't compact as soil does, drains better, and allows more air to get to the roots.

You'll find several discussions about various brands and mixes on the Gardening in Containers forum.

Dave

Kristy,

Different manufacturers blend all kids of different ingredients into their products labelled "potting soil" and "potting mix."

In fact, the same product from a national or international company may have different ingredients in a product with the exact same name or basic label. For example, a potting soil sold under the Scotts label might have composted rice hulls as a primary component if manufactured in Louisiana or Texas, while having composted pine bark fines as a replacement for the rice hull component if manufactured in Georgia.

Another thing you should be aware of is that both potting soil and potting mix might be essentially the same ingredients blended in different proportions. The fact that the label says "potting soil" does not automatically mean the product has "dirt" or "topsoil" as one of the ingredients despite what others may say. A "potting soil" may be composed almost entirely of composted bark fines, forest products, composted manure, and other products that have not necessarily ever been a part of a soils layer in the earth.

However, most "potting soils" contain some form of "dirt" in the strictest definition of the word, simply because the mix may have some sand, limestone, or vermiculite, all of which are sedimentary in origin. But then again, "potting mixes" also may contain mineral components such as sand, limestone or vermiculite which begs the question of whether they too should be designated as "potting soil" instead.

Now ... TOPSOIL Back when the Midwest was native prairie, the topsoil layer may have been a foot or two deep. It took 10 - 12 thousand years after the melting of the glaciers for Nature to form that layer of topsoil. It only took about 150 years of poor farming techniques to wash that layer of topsoil into the Gulf of Mexico.

Since it takes about 500 years for Nature to build an inch of true topsoil, nobody is gonna sell it for 2 dollars a bag or 60 bucks a pickup load. If you buy "topsoil" in a bag, or in a truckload from a nursery, I'll bet you're actually getting river bottom dredged silt, bottomland farm soil, or a manufactured product containing sand, silt, and a variety of composted leaves, garbage, sewer sludge, etc. Read the label ... if there is one.

So, back to Mix vs. Soil ... what are you getting in the bags labelled "potting mix" and "potting soil?" READ THE LABEL! If the product is packaged by a reputable manufacturer, the label will always have the components listed along with some other information that should give you a good idea what the product is intended for.

Bottom line: If you're starting seeds, rooting cuttings, growing plants indoors or that require a sterile, soilless medium ... make sure the label informs you that the mix meets your needs, is comprised of sphagnum moss, perlite, vermiculite, and other products and is sterile.

If you're filling containers to grow tomatoes outdoors, and the transplants are well beyond the stage where dampening off is an issue ... don't worry whether it says "potting soil" or "potting mix." Just read the label and pick a product that will give you a nice, loose-textured, well drained growing medium capable of retaining moisture but not becoming too soggy and not drying out to quickly.

Bill

Thanks all for your responses! Bill, your's was especially informative. Thanks again.