Here is an explanation from Tony Wroblewski on exactly what function Terra Flora performs in XP:
"It's a simple library replacement that updates all of X-Plane 11's default trees. Some important caveats:
- It only replaces default trees, it won't update payware products that don't use the default trees
- Scenery order is important. If someone uses another tree replacement product such as SD global, our product must be higher up in priority
- It doesn't do seasons
- It only replaces forest files and not tree objects (sometimes placed at airports)
- It does nothing to the TE regions, these already have it
In short, it should work great with the default and HD mesh sceneries as long as it's ordered correctly."