Potting mixes often contain sphagnum peat moss from bogs in Canada
or Ireland. Bark fines might come from a sawmill in the Deep South.
Coconut "coir," a peat moss substitute, gets shipped all the way from
A common ingredient in potting mixes is perlite, which makes the
soils airier while also retaining moisture. In its final form, small
white pellets, it appears to be something synthesized in a factory. In
fact, it comes from a volcanic sand mined on the Greek island of Milos.
Shipped to the United States, the ore is heated to 1,400 degrees
Fahrenheit, at which point it pops into kernels.
The always-interesting Joel Achenbach writing in the Washington Post.