Powis Castle’ is most likely a hybrid between Artemisia arborescens (large wormwood) and Artemisia absinthium (absinthe wormwood). It is a bushy, woody-based perennial or subshrub that is primarily grown for its aromatic, finely divided, silvery, fern-like foliage which is feathery in appearance. It typically grows in a shrubby mound to 2-3’ tall and as wide but spreads by rhizomes and may reach 3-6’ wide if not restrained.