Hugely popular - and deservedly so - Hydrangea macrophylla 'Nikko Blue' features large, rounded flower heads, up to 5 in. across (12 cm), densely packed with rich, deep blue florets. Blooming in early summer for up to 2 months, 'Nikko Blue' is very floriferous and produces new flower stems throughout the summer. The foliage is medium green with large, lustrous, serrated leaves. A classic name in mophead hydrangeas, it has become the standard against which other blue hydrangeas are measured.