The spike deformer is a great tool. I've also used the explode deformer to form a "cloud" of leaves -- very effective for distant foliage. I've found that if you deform and object and then jump into the vertex modeler with deformations still applied (or export the file to a different format then re-import it), the plant becomes far less difficult for the program to handle. That is, it's not having to calculate the deformed version of the object every frame. It makes moving these plant objects around much simpler. - Dex