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The Plant Guide

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‘Black Knight’ Butterfly bush

Buddleia davidii 'Black Knight'

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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 CharacteristicsNearly black flowers. Attractive to butterflies, hummingbirds, and bees. Easy to grow, but is in invasive in some areas. Fast grower.

CareEasy 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.

PropagationRoot semi-ripe cuttings in summer or hardwood cuttings in fall. Sow seed at 66-75°F  in spring.

ProblemsCapsid bug, caterpillars, weevils, mullein moth, spider mites. Fungal leaf spots and diebacks can occur.

  • Genus : Butterfly bush
  • Plant Width : 10 to 15 feet
  • Zones : 6, 7, 8, 9
  • Plant Height : 6 to 10 feet
  • Characteristics : Attracts Hummingbirds, Fragrant Flowers
  • Bloom Time : Fall, Summer
  • Growth Rate : Fast
  • Tolerance : Frost Tolerant
  • Light : Full Sun
  • Moisture : Medium Moisture
  • Maintenance : Moderate
  • Plant Type : Shrubs
  • Plant Seasonal Interest : Summer Interest
View Comments


  1. allinchessum 07/17/2017

    why does my buddleja davida have holes in the leaves ?

  2. user-7007343 09/20/2017

    It would seem appropriate to mention that Buddleia is an invasive species. Seedlings appear easily on any disturbed ground unless one is careful to cut off the spent blooms before they produce seed. I started with one Buddleia and now I have about five more of them than I want, even making a big effort to deadhead, and treating any new seedlings that pop up like weeds. Probably this winter I will rip out all but one of the established bushes - the one whose flowers are a very attractive magenta.

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