Sweet Flag

Sweet Flag (Acorus gramineus)

Dwarf Sweet Flag, Japanese Sweet Flag, Grassy-leaved Sweet Flag

Part sun to full shade, consistently moist to wet, tolerates standing water and clay soils, pH 5.5–7.5.

6–18 inches tall and 6–12 inches wide depending on cultivar; inconspicuous spadix flowers appear in summer; spreads slowly by rhizome to form dense low clumps.

Propagation by division in spring or fall; divide every 3–4 years to maintain vigor.

Native region: Not native to Tennessee; ornamental introduction from East Asia (Japan, China).

Acorus gramineus is one of the few grass-like plants reliably suited to permanently moist or waterlogged soils in Middle Tennessee — a useful choice for bog edges, rain garden borders, and consistently wet clay spots where other ornamentals struggle. The foliage is aromatic when bruised, with variegated cultivars ('Ogon', 'Variegatus') offering gold or white-striped blades. In Zone 6b/7a it is reliably root-hardy; hard winters may burn foliage but plants resprout from the rhizome. Deer generally avoid it. Not a true grass — classified in the family Acoraceae.