Lin, the city would make you take out a permit? That's so odd. In Hillsborough County, you can take out a tree on the invasive list no matter the size. They even have a list of the trees on the county website. My dad and his woodturner friends salvage wood for their hobby so they know a lot about which trees you can take down. And some of the invasives make for good turning wood, like Camphor. Don't get me started on HOAs!