I am curious to see who uses this, for what, and at what strength

I have been using Superthrive at the rate of a few drops per gal on orchids,
bonsai, and other plants for 20 years, about once a week. I think it does help.
One of the orchid growers did a study & found it helpful. Since it is not
terribly expensive by the pint, I would just as soon use it. Roots2 is similar,
but it stains terribly, so I only use it outdoors.

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)