I've searched back for this and didn't see anything, so sorry if it's a dupe. Sometimes I'll cut down trees on an island and don't return to that island for three seasons to a game-year and notice they're still just tree stumps. I also have a perfect line of palm trees on my base island that I see all the time. I cut them all down once and only one tree has grown back. It's kind of a random problem I can't recreate or see a pattern to. Some trees actually do grow back, but others don't.
Steps to Reproduce
cut down tree leaving the stump, come back after a while and see if it's grown at all
cut down tree leaving the stump, come back after a while and see if it's grown at all