Black mondo grass (Ophiopogon planiscapus 'Nigrescens') isn't a true grass; true grasses belong to the Poaceae family. Black mondo grass is, instead, a tuberous-rooted perennial in the lily family. It's a stemless plant on which the leaves sprout from the ground in clumps. In summer, a single flower stalk sprouts, carrying small, bell-shaped, pinkish flowers. This grass-like plant is often used as a ground cover for semi-shady areas, or in the front of a border or as an edging plant. It's common in rock gardens and valued for its unusual, black foliage. It makes for a great contrast with a plant like Sedum rupestre 'Angelina.'