use a professionally balanced media made for trees

and keep black pots out of direct sun on the pots ...

Hmm... I do have them on the north side of the lanai. They get filtered sun during the day, and direct sun in the late afternoon. Are you thinking soil temp is too hot? Or there is something in the soil?

You need a properly formulated potting soil, not a concoction made up of tree debris and sand or whatever. While your media may appear to drain well, it will have a high layer of fully saturated soil that will persist (a perched water table) and what you describe sounds exactly like the resultant root rot from this PWT.

Check out some of the 1000's of posts in the Container Gardening forum that discuss this in considerable detail.

1) > "trees potted in one and two gallon containers" ---- Probably too shallow.

2) >"Live Oak)...for potting" ---- Detrimental PER SE.

Could be the pot soil is getting too hot and the roots are cooking.

10% loss doesn't sound bad to me. It's summer in Florida. (But possibly no one will agree with me!)

with a bed of LO leaves

If this means they are sitting on old leaves with soil close beneath or directly on soil with leaves around them they may be getting infected by something in the soil. You want instead to have your pots sitting on a layer of a clean (no soil particles) stone material such as washed gravel, deep enough so that there is never any puddling around the bases of the pots.

There are thousands of huge container nurseries all over the south. They all use black plastic nursery pots in assorted sizes and place them in the full blazing sun unless they are a specific shade loving species.

I had a small (11 acres) container nursery near Charleston, SC filled with thousands of woody trees, shrubs, and groundcovers. Never once was overheating a consideration, not for me nor any of the other nursery owners.

Corkball needs to invest in a coarse potting mix as I expect that that's the reason for his problems.

I was told by a citrus grower/vendor that oak leaves tend to encourage fungal/bacterial problems for citrus trees.

I agree that doesn't seem like a good potting medium - maybe for azaleas...

ok that is good to know, thx guys

You can use a general potting mix and add pine fines, perlite, osmocote and a little coarse gravel to your mix. This is what I use for my potted citrus, plumeria, and tropical fruit trees etc. This keeps them well drained and doing well. I used to repot every few yrs but many have grown too large for me to manage so I just throw a little rabbit compost manure and new potting soil mix on every spring and it has worked just fine.