Trees in pots
If you have the space and pots I think it can be of great growth benefit for some trees. A few years ago I was able to purchase several hard plastic original style root-maker pots from a small nursery. Based on recommendation from the seller, over the past several springs I have re-potted several small white oaks, Asian pears and crabapples in these (4 gal pots I think) using the 'not-so-good' soil (a lot of clay, not potting soil) in my garden (for 1 year only). The pots are buried ground level and mulched just like you would be planting the tree in the wild, but with the advantage of regular watering, fertilizing and wind protection. For me, growth is probably 3 to 4 times greater than in the wild.
Each spring I dig the pots out of the ground and take them to their new home where the pots are removed and the entire soil/root mass is planted. The large soil/fibrous root mass really gives these trees a great start now because you now have soil that will retain moisture (unlike potting soil) and the new surrounding soil is often better, so the trees root easily.
Another thing I have started doing is buying reduced priced trees from Lowes and Menards late in the spring (usually apple and pears, but peaches too). By now these big, leafed out trees are always badly root-bound, but that's ok. Un-pot and make sure to cut all of the circling roots off and remove some of the outer potting soil to insure this won't continue. The trees are then re-potted (with a good potting this time) in much larger nursery pots (cheap plastic ones with drain holes). I place them in small rows in the garden on old 2x4's so they drain and can be tied up so they don't blow over. I also mulch around the pot if I can get the free city stuff to keep roots a little cooler. With regular watering and fertilizing these trees develop great root systems as well. Key here is that they need to be planted in the fall either before or after leaf drop (cannot over-winter above ground in these pots). Just before transplanting I completely wash the roots free of the potting soil with a spray nozzle at home and wrap them in the a plastic bag so they don't dry out. These are like bare root trees now, but with a great root structure and no potting soil to dry out next spring/summer. Good luck!