Butterfly bush

 Buddleia Black Knight has deep purple-blue, almost black, flowers in elongated clusters on long arching branches up to 10 feet tall if not cut back, and half that size if cut back. They bloom from early summer to first frost. The foliage is willow-like and grayish green. Attractive to butterflies, hummingbirds, and bees. Easy fast grower in fertile, well drained soil and in full sun. Prune back or cut to the ground in late winter or early spring and deadhead regularly.