I've been thinking of making my own potting mix. I would love to know how you mix yours @Sally PB .
I mix it in big plastic totes, the 16-17 gallon kind. WEAR A DUST MASK! Even if you're using stuff that isn't very dry, mixing it makes a lot of dust.
I use about 1/3 peat moss (this stuff can be very dry and dusty), 1/3 compost, 1/3 dirt from the garden. I add some perlite and vermiculite, and usually some organic fertilizer, like a 10-10-10 or 5-5-5. Some people add wood ash. I did the first year, forgot the second year, and haven't done it since.
Get it mixed as well as you can. I get in touch with my inner mud pie maker and use my hands. Then I wet it down. Using a watering can or sprayer will help; just dumping in some water usually doesn't wet it well. I usually take a couple of days to get it nice and moist, as it takes a while for the water to soak in.
I make my own compost = free. Soil from the garden = free. Vermiculite and perlite are left over from the first year I did this, so not free, but I don't know how much they were. The big bags are still about half full. I use probably 2-3 quarts (dry measure) of each when I make a big batch of mix. For the fertilizer, I'd say I use about 1 cup in big tote. Sprinkle it as you go, so it get dispersed better.
Peat moss is not free, but I get the best price at the end of the season. I get the biggest bale/bag they have, and it's usually enough for 2 years.
When I scoop the mix into the pots, it's still fairly dry. I try to wet it down over a couple days then, too, so that it's more uniformly moist. Fill the pots, give 'em a good drink. Water the soil again after planting seeds, depending on how moist it is.
Peat moss is really dry, I've found. It takes a while to soak up water. Just dumping some water on top doesn't work as well as sprinkling.