Originally Posted by User Name Taken
I wasn't sure when to take the ties/bamboo off of them (3 total trees). My Tulip Popular still is very flexible seems like. I've attached a pic of the whole tree. The sun made it difficult to tell, but the smaller upper half has quite a few reddish leaves and is obviously smaller than the bottom growth.
That bamboo stake is not intended to be used after planting. Looks to me like the tie might have partially girdled the tree, and quite possibly leading to the damage. You should have properly staked the tree once you planted it, assuming it needed to be staked at all. Avoid staking unless absolutely necessary. In other words, take the stakes out.
For your reading pleasure, I chased down a couple of sources on staking trees.