Most newly planted trees don't require staking. Gentle movement from the wind helps them develop a strong trunk and encourages the tree to send out deep roots, making it establish a stronger system for supporting itself. Trees only require staking if these conditions are an issue:
High winds that can flatten and uproot an unestablished tree.
The tree is tall but has a small root ball that will require time to grow strong anchoring roots.
Trees planted in open sites where there are no natural windbreaks from neighboring buildings, fences or hedges.
How Many Stakes?
A single stake is rarely sufficient for supporting the tree. Instead, it will pull the trunk in the direction of the stake, causing it to lean or to develop a bent trunk. In most cases, two stakes are sufficient if they are placed opposite each other. If the area is exposed to high winds, a third stake can be used to create a more stable support.
Flexible stakes made of thin wood work best. This allows the trunk some movement while still providing necessary support. There are also metal tree stakes available that are made to have some give.
Where Do the Stakes Go?
Stakes should be placed on the outside of the rootball so they don't penetrate and damage the roots. If you use two stakes, place them opposite of each other. Space three stakes at an equal distance apart. You must drive the stake 10 inches into the ground so it doesn't pull out as the tree sways. Choose stakes tall enough so you can tie the trunk at the point about 8- to 10-inches beneath the first level of branches.
How Is the Trunk Tied?
Flexible ties that won't cut into the trunk are best. You can use old bicycle inner tubes or purchase rubber-padded ropes specifically made for tying a tree. Wrap the tie around the stake and then cross the ends before wrapping it around the trunk and tying it closed. This creates a figure-eight shape, which prevents the tie from constricting the trunk too tightly. Repeat for each stake.
The ties should be level between the trunk and the stake. Don't pull them so they slant up or down toward the tree.
When Are the Stakes Removed?
It's best to monitor the tree throughout the entire summer season. Remove the tie promptly if you notice any damage to the trunk, such as worn bark or girdling. In most cases, young trees only require staking through their first winter, so you can remove the ties as soon as growth resumes in spring. You can leave the stakes in place longer, because they will provide a handy barrier to prevent the lawnmower from getting too close to the trunk.
With proper staking, your newly planted tree will produce a strong, straight trunk. (Go here for more questions about tree care)