The impression I get from potting media that advertise they contain fertilizer is much like the bread wrappers that say "made with 100% whole grain wheat flour". While it's true that the bread might be made with 100% whole grain wheat flour, they don't tell you that the 100% whole grain wheat flour only makes up a tiny percentage of the flour used to make the bread. Even if it only contained 1% wheat flour, it wouldn't be a lie. Most of the media I see has a few fertilizer prills just so they can make the claim it contains a starter charge of fertilizer, but I wouldn't bet on the amount it contains being sufficient, or that you can rely on not having to fertilize for whatever interval they asdvertise on the package. Caveat emptor!
Al
