There are certainly some computer programs available... You might want to check out Amazon.
However, I am a bit skeptical about these kinds of programs. In my opinion, they cannot replace a skilled landscaper.
How about using SketchUp? It creates 3D models, and you only need to import the 3D models. You can add all the text you want, and all the 3D models will appear. I used it to design my room. Or you could just use The Sims 2 🙂 😀:p