Sweet flags look like small ornamental grasses, but they're actually related to calla (Zantedeschia). Grown for highly attractive foliage. Use in damp borders, at pond edges, in shallow water, or average garden soil. Propagate by dividing clumps in spring or fall.
A. calamus. SWEET FLAG. Native to the Northern Hemisphere. Sword-shaped leaves resembling those of bearded iris are 1 in. wide, 45 ft. long, growing in a clump about 2 ft. wide. Foliage is fragrant when bruised, as are the thick rhizomes. 'Variegatus' has very showy white-edged leaves. Dies to the ground in winter.
A. gramineus. JAPANESE SWEET FLAG. Native to Japan, China. A trouble-free plant that prefers moist, fertile soil, either boggy or well drained. Fans of narrow, 6- to 12-in.-long semievergreen leaves rise from the ends of slowly creeping rhizomes; the plant eventually forms a rounded clump. Excellent for massing, combining with coarser-leafed plants, or growing in containers. 'Ogon' is especially showy, with arching golden yellow leaves to 10 in. long; it looks great beside dark green, burgundy, or purplish foliage. 'Variegatus' has white-striped green leaves; leaves of 'Licorice' are 112 ft. long, with fragrance and flavor of licorice. Dwarf A. g. pusillus, 35 in. high, and lime-green 'Minimus Aureus', 23 in. high, spread very slowly and are useful between stepping stones or tucked into niches in a rock garden.