Unity scale is inconsistent

The free assets from Unity are inconsistently sized. When I paint trees on terrain, the Sycamore trees are a fraction of the size of the FPS prefab. But while the palm trees seem to be proportional to the FPS prefab character, they don't draw until they are about relatively 5 feet away. They just remain "billboards". What is up? I followed these tutorials exactly and am getting different results: http://www.wonderhowto.com/how-to-create-island-terrain-unity-3d-game-engine-261277_3/