The rules for planting a tree have changed over the years, according to Richard Johnson of Penn State.

The time of the year the tree is planted is important, but the most important consideration is the speed of the replanting after it has been dug. Plant the tree as soon as possible after is has been dug.

The planting hole should only be as deep as the height of the root ball. The hole should be funnel shaped, with the bottom being only as large as the root ball. The top 6 inches of the hole is much wider, as this is the area where most of the root growth will occur. The hole should be refilled with the soil that was removed. A small amount of compost can be added, but is of little benefit.

If the root ball is covered with cloth burlap, it should be loosened but doesn't have to be removed. Plastic burlap must be removed. Burn a small piece if you are unsure of the type. Cloth will flame, but plastic will just smoke and melt.

Do not prune the tree. The old theory was to reduce the size of the tree so the disturbed root system could support the tree. Also, it was thought that it divided the vigor of the new growth over a smaller number of growing points. The experts now believe that all of the foliage is needed to supply the root with the energy that is absorbed by the leaves from the sun.

Staking is no longer recommended. It should only be used with trees growing in a very windy site and the stake should be removed after six months.

If you do stake for six months, the wire around the stem should have a loop large enough so that the stem can move freely in the wind. When the breeze moves the stem of the tree, chemicals called cytokinins cause the cells in the stem to thicken and enlarge, thereby strengthening the tissues. When a tree is staked, the stem does not move and the cytokinins are unused. Over time, the artificial support that the stakes provide actually encourages weak stems and top-heavy canopies. Then, if the stakes are removed, the tree is more subject to splitting and windfall than it would be if left alone.

The tree should be watered immediately after planting. Making a berm around the planting to hold water is not recommended; the berm has a tendency to hold too much water.

Mulching is recommended and should be 2- to 3-inches thick. The mulch should start several inches from the stem and cover the area to the drip line of the tree. The mulch, regardless of the type, should never touch the stem of the tree. When mulch does cover the bark, the area covered becomes an ideal habitat for rodents that may also eat the bark. Insects harbor in these areas and lay their eggs. Fungus diseases are the most common problem in the areas. The mulch prevents the bard from drying and rot and other diseases can then proliferate with eventual demise of the tree.

Wrapping of the stem, except in freezing weather is also discouraged because it provides a home for insects and slows the natural thickening of the bark. A winter wrap can protect the bard from sunscald, which causes the bark to split. It also prevents animals from gnawing on the bark.