Dig a hole in the soil the same size as the pot it came in, then drop it in and you will have a dead tree or a slow growing tree with strangled roots. Not what you wanted? Keep reading.
Plan on 3 hours per tree and assemble your materials before hand. You will need a bag of potting soil, or, if the worms and time have produced an inch or so of black rich top soil, that may be used for the potting soil. The rest of the materials are just the standard shovel, three-prong, hand-held rake, tarp for mixing dirt, ruler, straight board for checking average ground height, and gloves.
I suggest reading the following paragraphs before removing the tree from the pot so the roots are not exposed to air any longer than necessary. Spread out a tarp, scrape any good topsoil and put it on the tarp, then dig out a smaller than estimated hole and put the clay on the tarp. Then follow the paragraphs below.
The hole depth should be 1-inch less than the height of the root ball. This is not the height of the dirt in the pot.
To determine the height of the root ball you will have to remove the tree from the pot and use a three-prong, hand-held rake to spread out the roots at the outside edge and bottom of the root ball. Straighten any obvious roots curving around the root ball. Now you will know the true height of the root ball and can dig the hole. I have found that a 5-gallon potted tree is about 11 inches tall coming from the nursery, but only about 9 inches tall after raking.
The hole diameter ought to be about 2 times the pot diameter at ground level and equal to the pot diameter at the bottom. The bottom of the hole should be flat and left as undisturbed packed clay.
Set the root ball in the hole and adjust bottom dirt to to get the height of the root ball 1 inch above average ground level (remember the ruler and straight board for checking average ground height in the materials paragraph?). Mix clay soil dug from the hole with potting soil or black top soil at a ratio of 3 parts clay to 1 part potting soil and put about 3 inches of the mix into the hole. Spread any loose roots outward and tamp down the dirt, then moisten it. Moisten to decrease air pockets, not to make mud. Repeat the process in 3-inch increments to ground level.
For the last inch from ground level to the top of the root ball, use a 1-to-1 mix of clay soil dug from the hole and potting soil or black top soil.
The one-inch soil/clay cap above ground level will slow water penetration of heavy rains or watering, soak up water to allow it to uniformly wet the 3/1 mix below, and encourage root growth out into the better topsoil around the tree.
Three inches of mulch is a requirement not an option for a new tree. In the winter, ground-up leaves are great; in summer shredded wood is good. I am not a fan of pine bark.
After planting give the plant a good watering to settle and compact the dirt and close up air pockets. Keep the soil moist for a year. Donít let it go dry. In the winter I use 1-gallon milk jugs with the cap removed and a hole from a sewing straight pin poked in the bottom. I water the trees every 3rd day this way. In the summer more water is needed. A moisture meter measurement at 7 inches deep and 7 inches from the trunk is recommended. You donít want a mud puddle just moist soil.
Typical planting of a tree in a 5-gallon plastic pot