Umberto Oldani walks through how he created a scene with grass, flowers and a tree in Blender, using the freely available Arbaro Tree generator intended for POV Ray.

how to model the grass and the flowers, how to assign them the materials and how to render with Blender Render engine

Umberto shows how to model the grass, flowers and ground, and demonstrates how to add the flora material and render the image for composite. Check out the tutorial for Creating a grass and tree scene in blender here.