Mike,
Great pictures, Thanks for posting.
I will be planting most of my older trees in ground this year, but all my 5 gallon buckets will be buried a few inches.
I have used Dolemite Limestone from the start last year, because I have been loosely following the Mittlieder method of gardening, using a "preplant mix" which consist of Dolemite Limestone-Epsom Salt-Borox(Boron). In my 5-1-1 container mix I add 1 cup of "preplant mix" initially, then add 1/2 cup of straight Limestone per month to the top of the container and mix into the top few inches only (stir). I have had very good growth and healthy looking plants.
Please keep us updated on their progress.