Grassy-Leaved Sweet Flag

You'll identify Japanese sweetflag by its grass like long, narrow, slightly curved leaves that grow 10 to 20 inches tall, forming a dense mound of fine textured foliage. This herbaceous perennial spreads by rhizomes to create a living ground cover in wet places. The leaves are pale green to blue green, arching slightly from basal growth. In late spring to early summer (May to June), insignificant green and yellow flowers appear on short spikes up to 4 inches long, followed by small berries. The plant grows equally well fully submerged, partially submerged, or in very moist soil, though it typically flowers only when at least partially submerged.

You can grow Acorus gramineus in full sun to part shade in soils with frequent standing water or moist to wet conditions, thriving in clay, silt, or sandy loam soils with a pH between 6.0 and 8.0. Hardy through zones 6a to 9b, this plant has moderate to high water needs and reaches just 1 foot in height and spread. Plant 8 to 12 inches apart to allow room for rhizomatous spread, and maintain consistent moisture since soils shouldn't dry out. High maintenance is needed to manage its vigorous spread. Use it along streams, in rain gardens, at pond edges, in wet woodlands, or in containers kept consistently moist. The cultivar 'Ogon' offers golden foliage for seasonal color.