There are currently two methods of modeling and showing Planting families within Revit: RPC and solid geometry. The RPC (Rich Photo-realistic Content) trees are represented by two intersecting planes of a tree in elevation.
Graphically, they usually appear as shown above, but they will render out as a photo-realistic tree (below).
RPC trees look a little better, in my opinion, but they have a few drawbacks. Mainly they are not solid, 3d geometry and so are not suited for clash detection. So while solid trees may be a bit simplistic in appearance they are essentially more functional.
Here are a few examples I have seen recently of solid trees…
Now, I understand the need to have a solid, 3D tree, but graphically they often make me cringe. And though it is important for a BIM model to have good information, those models are also frequently used for renderings.
So why not have both? By combining both RPC and solids into a single Planting family you can have the benefits of both. In fact, I think having the RPC outline as a reference results in a nicer solid tree. Here is a single family, with 15 different types. The above trees are the same tree, just in solid form.
The solid geometry is a nested Planting family, with a variety of 6 different Form Types forming the canopy.
The solid geometry is a revolve created mostly from splines so that it can scale correctly for both Height and Width. The Canopy Ratio controls the height of the canopy and trunk (should be set between 0 and 1). The visibility of the RPC or solid is an instance parameters, but it could just as easily be controlled via Subcategories or a Detail Level Visibility Setting.
If you want to check it out, here is the RPC and Solid Planting Family.