Vermiculite and Make-It-Yourself Potting Soil

I've gotten tired of buying bags of potting soil. There's umpteen choices at the local box stores and garden centers, but I doubt the seeds care all that much what they grow in. Also, I've found some of the potting materials I've tried don't work all that well. They form a water-impermeable layer on top and when I water the pots, the water doesn't soak in.

Somewhere, I read that all you need for potting soil is a 50-50 mix of Vermiculite (an expanded form of mica) and peat moss, with maybe some slow-acting fertilizer thrown in. I gave that a try and, low-and-behold, the seeds grow! Now the problem is finding vermiculite. Most garden centers have cute little bags of it, which is fine, but I had visions of saving money and those little bags cost as much as a bag of potting soil. An online search for vermiculite didn't turn anything up. My closest garden center (Home Depot, ironically) doesn't have large bags. I asked about special-ordering it at one specialty garden center, but their supplier had stopped carrying large bags.

I put the big-bag concept on the back burner, but one day on my way into the big-box Home Depot I spied large bags of Vermiculite, just sitting there. I shelled out $27 or so and now I'm set for a while. The photo shows the bag I bought, along with the organic fertilizer I've been using. Of course, I'm out of peat moss, but that's easier to find.

My potting soil recipe.

Ingredients:

Some vermiculite
Some peat moss
Much less organic fertilizer (say 5-3-3).

Put some vermiculite into a five gallon bucket. Add about the same
amount of peat moss (you can go 60-40 on the peat moss/vermiculite mix
if you want to save vermiculite). Mix it. Add a bit of fertilizer
(optional) and mix some more.