1. Accent. A shapely plant such as spiky-leafed phormium is a natural standout among low, mounding plants. When its foliage is a rich chocolate hue, the heightened drama makes it a focal point.
2. Backdrop. A hedge of deep brown foliage ― Japanese barberry 'Atropurpurea', for instance ― looks striking behind a mass planting, such as gloriosa daisies with their knobby brown centers. Sunset climate zones A3, 2b-24.
3. Depth. Planted at the far end of a border, with soft greens or pale colors in front, a pillowy dark shrub or ornamental grass creates a subtle sense of distance.
4. Contrast. When used as a companion for flowering plants, deep velvety brown foliage makes flowers in clear, bright colors ― flaming red, lime green, golden yellow, or cobalt blue ― appear even more luminous.
5. Frame. A low fringe of brown foliage forms a distinctive edge for beds filled with mounding plants. Try Phormium tenax 'Jack Spratt' (zones 5-9, 14-24, H1, H2) with Million Bells Calibrachoa 'Crackling Fire' (zones 8, 9, 14-24; annual elsewhere).