Does growing media pH change in the package?
Most professionally produced growing media are composed of any combination of the following physical components: Sphagnum peat moss, aged/composted soft or hardwood bark, wood substrates, coir, compost, perlite, vermiculite, pumice and/or rice hulls. The component percentages vary based upon the type of growing media and its intended use.
Read more at the PRO-MIX website.