The use of vegetation could become a challenge for an exterior visualization project, especially if you don't have the right assets. It could be only grass or a small collection of trees. When you get the right objects at the scene, a landscape will become a significant contribution to the visualization project. Do you want to see an example of that?
At a project that has a name of “On the terrace” we can see how much the use of good quality vegetation can contribute to a render. The project is from Blender artist janmorek and is available with some different views at the BlenderArtists forums. Besides the image that illustrates this post, you will also find a night render of the scene.
Unfortunately, we don't have much information about render times or the hardware used to render all images. According to the artist the images at the forum are extra renders from a commercial project. They didn't get to the final project.
If you want to check the night view of the scene and a clay render, just follow the link to the forum.