Black Knight Butterfly Bush Buddleja davidii 'Black Knight' Description Blooms fragrant large dark purple flowers. Long stems with gray-green foliage. Bloom Period: SummerGrowth Habit: Rounded and vase-shapeMature Height: 5' to 6' (150 cm to 180 cm)Mature Spread: 4' to 5' (120 cm to 150 cm)Growth Rate: Fast More Details Sun Exposure: Full SunCold Hardiness Zone: 5Attracts butterflies and beesRabbit and deer resistantCut flowerGarden Tip: deadhead to promote re-blooming