Muehlenbeckia Complexa
It's hard to find room for a plant which has neither showy flowers nor evergreen leaves to boast of, however, Muehlenbeckia deserves a spot in many gardens.
It shines planted alone, as the finely textured, black stems are the perfect foil for the astonishingly round, glossy leaves. It is both tough enough to look after itself and fast enough to be noticed despite its diminutive height, plus it quickly forms a dense mat which weeds are unlikely to penetrate.
Why mulch your rose garden with bark dust when you could mulch it with wire vine? That long, grey, unbroken retaining wall could look more like a living waterfall.  Architectural round leaves give an effective illusion of water flowing when trailing out the side of a pot or over a rock wall. Black stems provide excellent contrast for the glossy, mid-green leaves.4"H x 20-30'W.