Knock Out' is a medium, bushy shrub, 2 to 4 ft (60—121 cm) in height with a 3 to 4 ft (90—120 cm) spread. Blooms are 2—3 in (5—7 cm) in diameter, saucer-shaped, with single to semi-double (5—13) petals. Flowers open from attractive buds, and are a bright cherry red with a white center and green-yellow-stamens. Flowers have a strong, fruity fragrance, and bloom in flushes from spring through fall. 'Knock Out' is disease resistant and blackspot resistant, but is susceptible to mildew. The shrub has glossy, dark green foliage. New stems and growth are purple. The plant thrives in USDA zone, 4 and warmer.