Texture is Your Friend
Like color, texture can also create the illusion of distance. Plants are divided texturally into three categories -- fine, medium and coarse [source: Cornell University]. These distinctions are based on the way a plant reflects light. A fine plant with lots of tiny leaves reflects lots of light and tends to form an airy whole. Coarse, large-leafed plants include lots of gaps where shadows can hide, creating a starker contrast between light and dark.
Like warm-colored plants, coarse-textured plants tend to catch the eye. Fine-textured plants, like plants with cool colors, demand less visual attention and therefore fade into the background and seem more distant. By creating a textured visual line away from your garden's focal point, with the coarsest plants nearest the center and fine-textured plants farthest away, you can create a false impression of distance. The eye of the beholder will be fooled.