Many gardeners like to stake trees when planting them to ensure that the trunk remains upright. That’s fine, but … the stake has to be removed as soon as the tree is well established in its new location, normally 12 months later, at most after two years. If not removed, the trunk will not develop normally. That’s because moving in the wind actually thickens the trunk and makes it stronger. A staked trunk can’t move correctly and will remain thin and subject to breakage.
You also have to remove the strap used to attach the tree to its stake. I stress this, because too often I see people remove the stake, but leave the strap in place. If left on the tree, it will eventually eat into the bark, as the trunk thickens over time. This will eventually strangle the tree (this is called girdling), preventing the sap from flowing. So remove it when you remove the stake … usually one year after you plant the tree.
Do note there is no special season for removing stakes. Do it whenever the tree seems solidly rooted.