Easily grown in average, medium, well-drained soil in full sun to part shade. Tolerates wide range of soils except poorly-drained ones. Appreciates some afternoon shade in hot summer climates such as St. Louis. Not reliably winter hardy throughout USDA Zone 5 where a winter mulch is advisable. Easily grown from seed or may be propagated by root cuttings best taken in early spring. Can spread aggressively by creeping rootstocks, particularly in loose soils. Can be slow to establish in the garden, but somewhat difficult to eradicate once established since small sections of root left behind can sprout new plants.
Acanthus spinosus, commonly called bear’s breeches, is a clump-forming perennial which is grown as much for its attractive foliage as for its architecturally bold flower spikes. Features pure white, snapdragon-like flowers enclosed (hooded and subtended) by spiny, reddish-purple bracts and arranged in vertical rows on substantial flower spikes which rise well above the foliage mound to 3-4′ tall. Blooms from late spring into mid summer. Deeply-cut, arching, glossy green, spiny, thistle-like leaves (2-3′ long) form an ornamental mound of long-stalked, basal foliage which usually remains attractive throughout the growing season. Similar in appearance to Acanthus hungaricus ( A. balcanicus), except the leaves of A. spinosus are more deeply cut and have rigid spines (hence the species name) at the lobe tips.