Black Knight Butterfly Bush

'Black Knight' earns its name in the garden every summer with flower spikes so deeply pigmented they read as nearly black in certain light — a dark violet-purple of remarkable saturation that has no close rival among butterfly bush cultivars. The elongated, cone-shaped panicles, reaching up to 10 inches in length, are borne in abundance at the tips of the current season's arching branches from June through September and often to the first frost, creating a late-summer presence in the landscape that few other flowering shrubs can match for sustained impact. Each spike is sweetly and honey-fragrant, and the combination of rich nectar and intense color makes 'Black Knight' an exceptional magnet for butterflies, bees, and hummingbirds — an effect that animates the plant throughout its long bloom season in a way that makes it as much a wildlife experience as a horticultural one. The gracefully arching branches, clothed in lance-shaped dark green leaves with distinctive white-felted undersides, give the shrub an elegant silhouette even when out of flower. The RHS Trial of Butterfly Bushes noted of 'Black Knight' in 2008–2010 that it offered a "unique dark colour" and that no modern form had been produced with equivalent depth of pigment — a distinction that holds true today and explains its enduring commercial staying power more than six decades after introduction.

'Black Knight' grows as a vigorous, fast-growing deciduous shrub reaching 5–8 feet tall and 4–6 feet wide in Zones 5–9, though hard annual pruning in early spring — cutting stems back to a low permanent framework just above the previous year's base — keeps plants more compact at 4–5 feet and dramatically improves flower production by directing the plant's considerable energy into fewer, longer, better-developed spikes on vigorous new growth. In colder reaches of its range, stems may die to the ground in winter but the plant resurges reliably from the roots each spring. It demands full sun and performs in a wide range of well-drained soils, tolerating poor fertility, drought once established, and even compacted urban conditions — a reflection of its species' origins on rocky mountain slopes and limestone outcrops in central China. Deadheading spent spikes during the bloom season encourages continued flowering. Gardeners in Oregon and Washington should be aware that B. davidii has been declared a noxious weed in those states due to its aggressive self-seeding in natural areas, and sterile or low-fertility alternatives may be more appropriate where invasiveness is a concern.

General care for any tree or shrub is easy, but like any living thing will require your attention. Please educate yourself and follow these simple rules.