Trees planted correctly will grow twice as fast and live at least twice as long as one that is incorrectly planted.

Containerized trees and transplanted trees should be planted in an area that is dug or tilled one foot deep and at least 5 times the diameter of the root ball.

If transplanting, be sure to keep the trees roots in soil. Do not bare root it.

Always handle the tree by ball, not by the trunk or branches. Do not let the root ball dry out.
Prevent root girdling by vertically cutting any roots that show tendencies to circle the root ball.
After the preparation, place the tree in the hole, pack soil firmly but not tightly around the root ball. Water the soil and place a protective 3-foot circle of mulch around the tree.

Keep the soil moist but not soaked after planting. Water the tree at least once a week, except for rain, or more frequently during hot weather. Dry soil below the surface of the mulch indicates time to water. As temperatures moderate in mid-fall, less frequent watering is required.

Mulch acts as a blanket to hold moisture, protects against harsh soil temperatures and reduces grass and weed growth. Good mulch choices are leaf litter, pine straw, shredded bark, peat moss and wood chips. Ideally, apply a two to four inch layer of mulch. More than four inches can cause a problem with gas exchange necessary for root growth. Do not cover the actual trunk of the tree because it may cause decay of the living bark at the base of the tree. Leave a one to two inch wide mulch-free area at the base of the tree to eliminate this problem.

Planting a tree properly grown and dug at the nursery will not require staking. Studies reveal that trees grow more quickly and develop stronger trunks and root systems if they are not staked at the initial planting. Protective staking may be called for where the tree is subject to lawn mower damage, vandalism or windy conditions. In this case, stake with two stakes and use wide flexible tie material to hold the tree upright, provide flexibility and minimize injury to the trunk. Support staking should be removed after the first year of growth. Protective staking can be left in place as long as necessary.

Reference: International Society of Arboriculture, The National Arbor Day Website & The International Society of Arboriculture