Butterfly bush Buddleia davidii 'Black Knight' Photo/Illustration: Steve Aitken 1 2 3 4 5 6 7 8 9 10 11 Butterfly bush (Buddleia davidii 'Black Knight') BUD-lee-ah dah-VID-ee-eye Genus: Butterfly bush Butterfly bushes are carefree deciduous shrubs that are reliably fragrant and easy to grow. Butterflies swarm to their blooms all summer long. 'Black Knight' has deep purple-blue, almost black, flowers in elongated clusters on arching branches to 10 feet tall if not cut back, and half that size if cut back. The blooms come from early summer to first frost. The foliage is willow-like and grayish green. Noteworthy Characteristics: Nearly black flowers. Attractive to butterflies, hummingbirds, and bees. Easy to grow, but is in invasive in some areas. Fast grower. Care: Easy to grow in fertile, well-drained soil in full sun. Prune back or cut to the ground in late winter or early spring. Deadhead regularly. Propagation: Root semi-ripe cuttings in summer or hardwood cuttings in fall. Sow seed at 66-75°F in spring. Problems: Capsid bug, caterpillars, weevils, mullein moth, spider mites. Fungal leaf spots and diebacks can occur. Overview Height 6 ft. to 10 ft. Spread 10 ft. to 15 ft. Growth Habit Clumps Growth Pace Fast Grower, Invasive/Aggressive Grower Light Full Sun Only Moisture Medium Moisture Maintenance Moderate Characteristics Attracts Butterflies, Attracts Hummingbirds, Fragrant Flowers, Showy Flowers Bloom Time Fall, Summer Flower Color Blue, Purple Uses Beds and Borders, Cut Flower Style Cottage Garden Seasonal Interest Summer Interest Tolerance Frost Tolerant Type Shrubs Buddleia davidii 'Black Knight'View the discussion thread.