Acorus calamus (Sweet Flag)

Ideal for wet areas, Acorus calamus (Sweet Flag) is a spreading, marginal aquatic perennial forming a tuft of erect, sword-shaped, bright green leaves adorned with one slightly wavy edge and a prominent midrib. In late spring, this plant bears inconspicuous greenish-yellow flowers in finger-like inflorescences, 2-4 in. long (5-10 cm), which give way to tiny, reddish berries. Both the crushed foliage and rootstocks have a pleasant aromatic fragrance. A great choice for naturalizing, Sweet Flag is quite versatile in the garden and makes a decorative foliage accent in water gardens and around ponds.

Ideal for wet areas, Acorus calamus (Sweet Flag) is a spreading, marginal aquatic perennial forming a tuft of erect, sword-shaped, bright green leaves adorned with one slightly wavy edge and a prominent midrib. In late spring, this plant bears inconspicuous greenish-yellow flowers in finger-like inflorescences, 2-4 in. long (5-10 cm), which give way to tiny, reddish berries. Both the crushed foliage and rootstocks have a pleasant aromatic fragrance. A great choice for naturalizing, Sweet Flag is quite versatile in the garden and makes a decorative foliage accent in water gardens and around ponds.

  • Grows easily about 24-30 in. tall (60-75 cm) and 18-24 in. wide (45-60 cm). This plant will slowly spread over time by rhizomes to form a dense ground cover. It is not considered invasive.
  • Enjoys full sun to part shade and thrives in medium to wet soils. Grows well in both boggy conditions including shallow standing water to 9 in. deep (22 cm). Do not let the soil dry out. Afternoon shade is appreciated in hot summer climates.
  • This is a graceful plant for water gardens, rain gardens, stream or pond margins, and bogs.
  • Low maintenance, this plant is generally disease and pest free.
  • Propagate by rhizome division at the beginning of the growing season. Pot up and plant out only when fully established. Divide every few years to prevent congestion.
  • Introduced into North America for medicinal, ornamental, and other purposes. Sweet Flag is native to India, Central Asia, and probably Eastern Europe.

Requirements

Hardiness 4
– 10

Heat Zones 2
– 11

Climate Zones 2, 2A, 2B, 3, 3A, 3B, 4, 5, 6, 7, 8, 9, 10, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Plant Type Aquatic Plants, Ornamental Grasses, Perennials
Plant Family Acorus – Sweet Flags
Exposure Full Sun, Partial Sun
Season of Interest Spring (Late)Summer (Early,Mid,Late)Fall
Height 2'
– 3'
(60cm
– 90cm)
Spread 1'
– 2'
(30cm
– 60cm)
Spacing 24″ (60cm)
Water Needs High
Maintenance Low
Soil Type Clay, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Poorly Drained
Characteristics Showy
Native Plants United States, Alaska, Midwest, Illinois, Indiana, Iowa, Michigan, Minnesota, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin, Northeast, Maine, Maryland, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Pacific Northwest, Idaho, Washington, Rocky Mountains, Montana, Southeast, Virginia
Tolerance Wet Soil
Garden Uses Bog Gardens, Ground Covers, Ponds and Streams, Rain Gardens, Water Gardens
Garden Styles Informal and Cottage