“a composted product that contains beneficial fungus known as mycorrhizae”<<<
This is something that I have no knowledge of, first thought was of mushrooms.....
Looking at google shows links to the product and information.
Garden Girl is in your part of the country, LOL, I forget if it is North or South Carolina she gardens in.
MaxMax knows composts and Diana will also.
Thank you for bringing up a subject we have not talked about and it looks interesting.
Both Diana and Garden Girl work in nurseries, so they may know if others have tried it.
There are several different species of mycorrhizal fungi, each offering specific benefits. The better products contain several for a good all around solution. With so many product choices, I would like to use something others have had success with rather than experimenting.
Last year's record heat and drought really stressed my leyland cypress trees. I've lost one, all the evergreen shrubbery in front, as well as several large bushes. After digging them out, I found the roots were mainly between the dirt and the mulch with the dirt being almost lifeless: no roots, earth worms, organic matter, nothing. Whoever did the original landscape didn't improve the dirt at all before planting.