Blue Boy - Tall Phlox

Blue Boy is a fragrant garden phlox with mauve-blue flower clusters marked by purple and white eyes. The RHS profile lists a mature height of about 90–120 cm and a spread of 0.5–1 m, with flowering from summer into early autumn. It grows in full sun and suits fertile, moist but well-drained soil; its clump-forming habit makes it useful in a mixed perennial border where the flower heads can rise above lower planting. Allow space for the mature spread and avoid letting the root zone dry for long periods during active growth. Its RHS hardiness rating uses the United Kingdom system, so this description does not translate that rating into a North American zone. See the [RHS Blue Boy profile](https://www.rhs.org.uk/plants/66975/phlox-paniculata-boy-blue/details) for the cultivar's flower, size, and position details, and the [RHS tall garden phlox guide](https://www.rhs.org.uk/plants/12736/phlox-paniculata/details) for general soil and growing conditions. ## Maintenance Water during dry spells, especially in the first season, and remove faded flower heads if you want to limit self-seeding. Cut old stems back after flowering or in spring.