About Artemisia ‘Powis Castle’: ‘Powis Castle’ is a bushy, woody-based perennial or subshrub which is grown for its aromatic silvery foliage. It rarely flowers. Foliage is finely divided and feathery in appearance. Typically grows in a shrubby mound to 2-3′ tall and as wide, but spreads by underground rhizomes and may reach 3-6′ wide if not restrained. Essentially evergreen in warm winter climates. This plant grows 1 to 2 feet wide and 2 to 3 feet tall. Zones 6 to 9.