I bought that Moisture Control deal at Costco to fill all my container gardening pots and it was a nightmare. Everything I grew in it died. It was a constant struggle to keep it wet. I'm not sure what it's supposed to do with a claim like "Moisture Control". I basically had a full time job trying to keep the plants alive that I'd planted in it. At the end of the season, I dumped all the pots and refilled them with different soil the next year. Very frustrating.

Ah, shucks. I was hoping that I'd found a cheap alternative to Mel's Mix. Thanks for warning me!

That's the stuff in the yellow bags right? I used it in a box last year and was ok, but that box is watered by a drip hose connected to my a/c condensation pipe so it got regular watering every day all day! To be honest though, I did add a bag of vermiculite to it this year because as mentioned above, it does still dry out relatively quickly (as do all soils in sfg).

It's the blue bags. It's not the same as the yellow bags. It's got some sort of wetting agent in it or something.

My girlfriend grows everything in the costco bags of MGPS, and has good results.

.. even with things that I don't think are a good match for that soil.

I suspect that it comes down to being responsive, and tuning your watering to the soil, rather than demanding that the poor soil respect your watering.

MiracleGro Moisture Control has been my go-to potting soil for several years, and I've had great success with it for flowers in containers as well as herbs and lettuces in my raised, square-foot garden bed. FWIW, last summer was fairly wet here in southeastern PA, so I hardly had to water at all. The only "problem" I encountered was that the Dragon Wing Begonias I planted in deck rail boxes got SO big and top-heavy, the boxes toppled off the railings.

I bought that same thing from costco for like 10 dollars for 2 cu ft. It is terrible, theres a weird yellow thing that grows on top of the soil after a while and it grows mushrooms like crazy in all my indoor plants.

If you consider, really consider what Mel indicates should be in his compost you'll realize it cannot be purchased.

Sometimes you can get some of the compost, peat, etc. in broken bags for less. I've purchased some of these at various garden centers. With my new beds I used a lasagna style filling before topping off with the transferred mel's mix from the old beds. I started with leaves we bagged from the fall, green leaves from weeds in the perennials, dried out perennial stems, then a layer of peat, layer of manure, layer of verm, layer of compost, etc until it was filled. I had good production. Getting too lazy (senior) to drag a tarp around to mix it all. The last bed was topped with compost I'd been making for a few years. My plants were amazing. Some of the longer carrot varieties grew straight down and then turned and continued growing sideways when they hit the weedmat. These are concrete block beds that are 8" tall.
Keski