Two things are important to freshly planted trees - moderate temperatures and rainfall. Ideally, any plant will have time to acclimate and to establish roots in their new enviroment before being exposed to any extreme weather. For those reasons, the best times to plant a tree are very early in spring (before leaves start to form) or towards the middle of the fall (after leaves have stopped growing). At these times, most of the energy of the tree will be spent on root growth. This is not to say that these are the only time to plant - just when the conditions are the best to do so. Locally (Southern Indiana) and with proper care, we may start planting in early March and continue until late November. In areas farther south with milder winters, planting may be done at any time of year.
Remove the tree from its container - If you are planting a B&B (ball & burlap) tree or a container tree, you should be careful to transport it from the bottom and not to pick it up by the trunk. A potted tree should be put on its side to remove the container. Try to gently loosen and gently spread roots before planting. If the roots are growing in circles at the botom of the plant, it may be necessary to make some cuts at the bottom of the rootball in order to spread the roots prior to planting. If the roots are left bound up, they will not expand and grow. The tree will not get any larger and will eventually die. B&B trees with natural burlap should have the burlap loosened and pulled away from at least the top half of the root ball (natural burlap repels water). If the wrapping is plastic or you are not sure, it should be removed entirely.
Plant tree at the correct height - the spot where the tree roots start to expand away from the trunk of the tree is called the trunk flare. The trunk flare should be visible when the tree is planted. It is better to plant the tree a little high as opposed to a little low - there will be settling over time.
Back fill around the roots - Amending the soil (adding compost/peatmoss/topsoil) before it is put back in is fine, but do not overdo it. You want to pack the soil back in the hole just firmly enough to hold the tree in place. Getting oxygen to the roots will go a long way in helping the tree establish - be weary of over compacting the soil around the base of the tree. There will be soil left over when you are done.
Staking - Some larger or top heavy trees may need to be staked after they are planted. Trees may also be staked where wind is an issue. Two stakes on opposite sides of a tree are usually enough. Stakes should be driven into the ground outside the area that was dug up to plant the tree. Use wire looped (once only) around the tree and attached to the stake. A short section of hose - cut and used as a ‘sleeve’ for the wire - should be placed between the wire and the tree. This prevents the wire from cuting into the bark of the tree and causing damage. Tension on the wire should be firm but not tight. Staking the tree prevents the rootball from shifting and tearing the newly established roots as they grow. Common mistakes to avoid: stakes too close to the tree, over-tightening the wires and not protecting the tree bark from the wire.
Mulch - A 2-inch layer of mulch around tree will help keep moisture from escaping. Take care to leave a 1- to 2-inch ring around the base of the tree that does not have any mulch. A short dam around the outside edge of the mulch will help collect rain water and direct it to where it is needed.