My bet would kind be to stay away from Meshes, but I’ve heard that Blender Tree’s are amazingly smooth. I would try Blender.
If you’d like to build the tree’s, here are some designs:
tree design’s don’t belong to me
Try not to use bricks for the leaves. Good luck!
Or use unions as an alternative…
We stress tested a ton of trees for our game. Meshes for trees are definitely the way to go, for large more complex trees. It will take a little longer to load in the beginning, but your overall performance is tons better.
Could you send me a video tutorial on that, or some instructions because those leafs look incredible!
Alike to many other people here, I also use meshes - which I’ve created in Blender.
It’s possible to create trees with a cartoony-ROBLOX feel in Blender, but also make them look pretty smooth and nice.
Performance-wise, using mesh trees cuts down lag by quite a bit, as they would only use a few parts each, compared to 30 (for a simple tree), and 150+ for a detailed tree! Using Blender, you can create both simple and detailed trees in less time, as well as cut down on loads of lag. 
On YouTube, there are many tutorials for creating trees in Blender. They’re all very simple, so you should check them out, depending on what style of tree you’d like.
Just wanted to add this: if you plan on doing your tree’s in studio, then make sure CollisionsEnabled is not checked for the leaves. This means the GPU no longer has to calculate the physics of the part (yes, this is a GPU operation; it’s not handled by the CPU), and therefore you receive way less lag. Another thing is to cut down on the render fidelity of the object by unioning and then changing the render property to automatic. The default setting is Precise. Switching it to automatic lowers the time the GPU spends drawing the part, leading to more time spent drawing frames and therefore less lag.
Note I’m relatively new and this could all be wrong, but from personal experience I’d say this is correct. If anyone wants to verify what I said, it’d be greatly appreciated!
