Planting a Tree on Public Land

What is the legality of this? Lets say theres a parcel of public state owned land thats just a grassy field. And I think a tree would look good right in the middle of it, so I go all on my own and plant a tree there. Most likely, nobody would care and everyone would just like there being a tree there now. Assume I'm fairly confident there are no utilities in that area that would be affected by tree roots. Its near roads but it has enough of it's own space that it wouldn't be causing visibility issues with the traffic.

If someone didn't like this and "turned me in", is this even a crime? Is it vandlism? Kind of feels like the opposite of that. This area isn't fenced in in any way and it's surrounded by road so its not like you're not supposed to be there.

The obvious answer is "just get permission" but this definitely seems like a situation where "ask for forgiveness instead of permission" is the better route to go. And I'm probably too lazy to actually go through the hassle but hypothetically, if I were to do it what would/could happen?