You might want to visit the Landscape Design forum and search the archives for this topic........it comes up frequently and various products have been suggested. And with varying degrees of recommendation :-) Some are very workable and user-friendly, others much less so. Generally the free programs are less flexible and efficient than those that are purchased. Like the graph paper/pencil route, design software is only a tool and will offer the best results with a good understanding of basic design principles and the plants and their requirements. Some find the pseudo 3-dimensional aspect many programs offer easier to visualize than just plan views created on paper. But you need to be cautious about some of the photoshop aspects, which can distort scale and spacing and alter perspective. And show everything blooming at the same time as well :-) Personally, I prefer the graph paper and circle template, but then I was trained in hand drafting and feel very compfortable with that method. Another handy tool is to take photos of the area in question, blow them up to a workable size and then do tissue paper overlays sketching in the appropriate plants at the appropriate sizes. That combined with a layout to scale on graph paper should get you a long way. There are also various DIY landscaping texts that would be helpful. Sunset's Western Landscaping, the companion to the Western Garden Book, is pretty good. My library is still packed or I'd suggest others but Lowe's and HD usually have a decent selection in their book/magazine area. Look through and find one that presents a reasonable discussion of design principles and a step by step method to preparing a design. That should help a LOT!

I would not visit the site above. This person joined today for the purpose of advertising the site and is listed as in Thailand. Googling bring up only 5 hits and 3 of those are in a foreign language. Could be genuine but................

Do not cause a false alarm. Webroot runs perfectly well on Win10. If you must reinstall it, it takes 45 seconds.

I used a free interactive graph paper. Tom Maitland. I then save the outline in paint and add stuff. I've bought various programs but I found them cumbersome and not custom enough. Some people love Sketchup but it was very hard for me to learn so I gave up on it.