Hummingbird Summersweet Clethra alnifolia 'Hummingbird' Description Blooms fragrant white spike-shaped flowers. Green foliage. Bloom Period: SummerGrowth Habit: Dwarf, upright and oval Mature Height: 2.5' to 3' (76cm to 91cm)Mature Spread: 3' to 4' (91 cm to 122 cm)Growth Rate: Slow More Details Sun Exposure: Full sun to partial shadeCold Hardiness Zone: 3Attracts butterfliesLong blooming flowersTolerate wet soilLandscape uses: Hedge or rock garden accent