This cultivar is one of the hardiest of all Buddleias. Buddleias are of course known for their prolific blooms and Black Knight takes it to a higher level. An extra-heavy producer, its blue-black flowers are particularly striking in direct sun. This beauty is also one of the hardiest cultivars of this group. In fact, it has been rated by the Arnold Arboretum as the best Buddleia of all. One of the most prolific sources of massed color, Buddleias have an exceptionally long blooming period that lasts from summer to early autumn. The long flowers trusses are a seemingly unending supply of cut flowers and garden beauty, and they attract butterflies and hummingbirds, too. Plants normally attain 6 to 8 ft. in height with a similar spread, though we recommend cutting back almost to the ground each year in late winter to promote heavier bloom.