This tall, upright hardy perennial is native to North America, and the description is all in its name: two beautiful gemstones of opposite colours. ‘Onyx’ refers to the plant’s dark, nearly black foliage and ‘Pearls’ to its tall spikes of soft white flowers washed with pink or lavender. Supremely effective in borders. Plant in fertile, well-drained soil, and deadhead on a regular basis. Cut back to the ground in the fall and cover with a layer of mulch.