There are several programs but they aren't cheap. I also note that many are not that user friendly. There was discussion on this subject in the landscape design forum a year ago. Better Homes and Garden has also a free online program but it's very awkward. Wouldn't you find it easier to simply get a graph paper and plot down your home, location of the permanent structures, etc. I finally did my plotting down this way, and it sure helped for easy reference. You can get tracing paper and superimpose it on the grid to let you freely draw plants over it.

Maybe check out this thread on another forum: Here is a link that might be useful: Design Software discussion

i tried using this site: http://www.smallblueprinter.com/floorplan/floorplan.html i have an older (2010) macbook pro and it seems to work great so far. i have not finalized my plans, so i am not sure if there will be further complications- but thus far, it is user friendly, free and fun! Here is a link that might be useful: smartdraw/blueprint program for mac

There is definitely an advantage to CAD as one can create objects, as opposed to just drawing pictures comprised of lines. Sketchup is the free or low cost CAD program, but it has a high enough learning curve to be discouraging to many. Though there are tutorials online. It might be one of those things that if you grasp some of the basics, it will begin to "flow." I don't know; I've never made it that far. Though it is just drawing, I like using MS Paint for plan and visualization, as it is simple ... good for anyone who understands perspective drawing. A simple base plan, since it is mainly lines, can be drawn on it with any computer, using the line and shape tools. The app has a built-in grid and measuring guide that can be toggled on and off. (The default scale is 1"=10', but it doesn't tell you that.) Compared to pencil and paper, it saves a lot of time if needing to erase, or when copying elements. And it is much cleaner. Since it's just drawing, it is not as precise as cad. For visualization, you can open any landscape photograph in Paint and draw over it, and copy and paste elements within it. However, since that process is not just drawing straight lines, it requires a touchscreen and stylus in order to use the program well.