A 3’x3′ deciduous shrub, ‘Dark Knight’ has the deepest blue color of any of its relatives and a profusion of flower clusters. Silver beneath the small lanceolate leaves augments the blue! Its habit is upright, rounded, and tidy, and it blooms on new growth, so if you’d like it to be dense and especially floriferous, prune it back hard in early spring. Even if it freezes back in a harsh winter, it’s likely to resurrect from the base. Butterflies approve of the flowers!

Minimum temperature: -20F