I think you captured the texture and color of the grass well, but the rock has no texture because it is in flat soft lighting unlike the grass which is in directional spot lighting. Although I see you've used the tree to frame the shot, there's not really anything there to be framed in my opinion. I'd suggest losing the tree completely (why not, it's not what you stated you want to show, right?) and just get up close and personal with the wall and grass. It would be a more obvious contrast between hard, jagged, and soft, lush. Perhaps choose a time of day when the light rakes across the rock and reveals it's true texture.