Although visibility (or occlusion) culling techniques have been extensively studied and adopted for fast rendering of occluded objects in a scene, rendering of botanical models poses a major challenge that is not well addressed before. That is, objects in natural scenes tend to be large in the number of counts (e.g. trees), yet they are usually made out of small primitives (e.g. leaves) which make traditional occlusion culling a non-trivial task. In this research, we present two techniques to simplify tree leaf objects for their fast rendering while retaining their visual resemblance to the original model.