I planted a dozen heirloom apple trees in the last few days! Very excited to see what they do.
It's only our second year but I understand so much more about planting trees than I used to, and this time I was able to add our own biochar and compost as well as other amendments. We have clay soil that seems to be high in minerals (we still have to get it tested) but the charcoal should help with both drainage in rainy seasons and water retention in droughts.
I took the advice of Billy from Perma Pastures and planted a nitrogen fixer (baptisia) in with each tree, and most of them have two or three comfrey cuttings planted around them as well.