i don't have any idea. i mix my own potting soil all the time. i buy peat moss, perlite, vermiculite & fertilizer by the bulk. so far so good. when i used to buy potting soil and top soil... i'd always had failures. since i mix soil for specific plants,i've been pretty lucky with plants i grow... ma vie
most of the potting soil sold is peatmoss, pearlite, wetting agents and some fertilizer. i find that this dries out to fast and does nothing for the plant. unfortunitly this is what most of the big places use you bring plants home and end up croaking good for the big nursery bad for you. what i like is one part spagnum moss and one part sifted compost or humas. for seed planting i sift my mix threw i 1/4 inch screen, for transplanting i just break it up mix well and use it as is
I notice you live in Florida so you probably have at least some sand in your soil to loosen it. Here in central Missouri most top soil is black clay. Hard, compacted, very poor for pots because it doesn't drain well and the roots have a hard time moving out thru it. We add tons of leaves, well rotted sawdust, completely decayed silage from the neighbors trench silo, stable cleanings from another neighbor & sand to it in our ground level beds and its still hard. Personally I recommend either the best professional potting mix you can buy(I just happen to like Fertilome brand)with Miracle Grow, etc. for watering or a mix of well rotted organic matter and peat moss. Personally I reuse potting soil after it has been outside for a season and add more organic matter to it. I use to do volunteer work at a botanical garden and brought home tons of discarded potting soil. I put it under the rabbit cages and let them add fertilizer to it, then reused it in pots and to replace soil in the ground for new transplants.
The Wal-Mart TOPSOIL seems very sandy. I ended up using it for starting seeds & had good results with that..better than some of the high price starting soil I bought. It was very soft & the little roots went right down.. I plan on using that again next year. I haven't tried it in pots yet.
As many pots as I plan to have I can't afford the expensive ones. I do add fertilizer when needed. We have a compost bin started with lots of leaves & grass to put in it. I hope to have lots of compost next year. We have a soil thermometer & the other day it was 150°
That should be good in pots.
If you need any of those black plastic pots you should drive over to Holt, Fl. A nursery is going out of business and he has a jillion. The gallon pots (I think that's the size) are .03 each, the little square and round ones are .01 each. He still had a few azaleas and some other shrubs when I was there Thursday. Azaleas (gallon) are .50, larger ones are $2.50.
Thanks for the info but think we will pass it up. We bought 300 square 3 1/2 inch pots off the net at a very good price. We don't use many gallon ones. We use more 3 & 7 gallon ones. I think I have plenty of them now. I wouldn't mind some scrubs but I have lots of stuff already that needs to be planted. A lady I met on another forum gave us a few azaleas last month plus a Hydrangea which I'm real happy about.
Edited to put in the word "inch"