Landscape plans are necessary, but 3D perspectives can give you a real feel for what the design will look like. Vectorworks has a camera tool so you can take a picture of your design and then render it realistically. Another helpful tool is to create a short animation, which is a virtual walk through, so you can see your design from a variety of viewpoints.
I also use a programme called Camera Match. You can take a picture of a site and then superimpose your design onto this. This is a quick way to give my clients an idea of what something will look like without having to model the building and surrounds.
The picture below is of a landscape in progress. The client wanted to put a shed there so I used Camera Match to put the shed design on that picture.
This is the same picture with the shed design over it.
This is a picture of the real thing. Looks very similar!