Black Knight butterfly bush (Buddleja davidii 'Black Knight') attracts plenty of butterflies, but it also attracts valuable pollinators, including the carpenter bee. From May through October, this cultivar produces numerous spires of mildly fragrant blooms on the ends of its branches; the flowers are deep violet with contrasting pink eyes. Butterfly bush is a half-hardy shrub. Its top is frequently killed to the ground in Chicago-area gardens, but it puts forth vigorous growth in late spring. It prefers full sun and moderate moisture conditions and will reach a height of 5 feet in this area. Plant 'Black Knight' in full sun, and water it well the first year to get the root system well established.