A borderline hardy, clump-forming, deciduous perennial with broad, strap-shaped, dark green leaves, flushed purple at the base, and, in early to mid-summer, sturdy, erect stems bearing dense, rounded umbels of star-shaped, violet-blue flowers with a dark purple stripe down the centre of each petal.
Height 1m (3ft), Spread 50cm (1.5ft), 2-5 years to maturity.