Which of the following is the correct name for the plant known for its striking purple foliage, Physocarpus opulifolius 'Diablo'?

The correct name for Physocarpus opulifolius 'Diablo' is indeed Diabolo Ninebark. This plant is notable for its distinctive dark reddish-purple foliage, which sets it apart as an ornamental shrub in landscapes. Ninebark, a member of the Rosaceae family, is well-regarded for its attractive bark and flowers in addition to its foliage color, making 'Diablo' a popular choice among gardeners seeking visual interest throughout the growing season.

The other names listed do not refer to this specific plant. Red Twig Dogwood refers to a different genus and species, known for its vibrant red stems in winter. Summersweet is a common name for Clethra alnifolia, a flowering shrub appreciated primarily for its fragrant white or pink blossoms. Maiden Grass is a type of ornamental grass, specifically Miscanthus sinensis, which does not share the same physical characteristics or genus as Ninebark. Understanding these distinctions helps in accurately identifying and utilizing landscape plants.