Acanthus

Bear's breeches is a bold Mediterranean perennial whose dramatically lobed, glossy leaves inspired the Corinthian column capital of classical architecture. Its wild native range spans the central and eastern Mediterranean - Italy, Sicily, Sardinia, the Balkans, Greece, the Aegean, Anatolia and the Levant, plus NW Africa (Morocco, Algeria, Tunisia); it is naturalised (not native) further west into Iberia. In gardens it serves as an architectural statement plant, producing tall white-and-purple flower spikes in summer on established clumps. The honest catch is its root system: fleshy, deep-running tuberous roots regenerate readily from the smallest fragment, making Acanthus mollis genuinely difficult to eradicate once established and a declared invasive in Australia and New Zealand, so site selection is a permanent decision.

Spiny bear's breeches (Acanthus spinosus) is a bold architectural perennial of southeastern Europe and the southern Balkans, grown for its foliage as much as its flowers. It builds a mound of deeply cut, arching, glossy dark-green leaves to about 60 to 90 cm long, and those leaves are the point of difference from the commoner Acanthus mollis: they are far more finely divided and carry rigid spines at the lobe tips, so the plant is thistle-like to the touch rather than soft. In early to midsummer it sends up stiff spikes to about 3 to 4 feet, set in vertical rows of pure white hooded flowers under spiny reddish-purple bracts. It is generally rated the freer and more reliable flowerer of the two garden species and holds the RHS Award of Garden Merit. The honest catch is the same as A. mollis: deep, fleshy, brittle roots that spread by creeping rootstock and regenerate from fragments, so an established plant is slow and difficult to move or remove, and the leaf spines make digging it out an unpleasant job. Site it as a long-term decision.