Common Name: sweet flag
Type: Herbaceous perennial
Zone: 4 to 10
Height: 2.00 to 2.50 feet
Spread: 1.50 to 2.00 feet
Bloom Time: Flowers not showy
Bloom Description: Green
Sun: Full sun to part shade
Water: Medium to wet
Suggested Use: Water Plant, Naturalize, Rain Garden
Tolerate: Heavy Shade, Erosion, Wet Soil
Easily grown in average, medium to wet soils in full sun to part shade. Grows well in both boggy conditions (including shallow standing water to 9” deep) and consistently moist garden soils. In water gardens, plant rhizomes slightly below the soil surface in moist soils at the water’s edge or in containers set in shallow water. Rhizomes or existing clumps may also be planted in containers sunk into wet boggy areas to help prevent any possible aggressive spread. Scorched leaf tips will occur if soils are allowed to dry out. Appreciates some relief from hot summer sun (e.g., afternoon shade or filtered sun) when grown in hot summer climates such as the St. Louis area. Slowly naturalizes by creeping rhizomes and can form large colonies in the wild.
Sweet flag is a deciduous, spreading, marginal aquatic perennial that features iris-like, sword-shaped leaf blades (to 3/4” wide) typically growing to 30” tall. Mature leaves have one wavy edge and a prominent midrib. It thrives in wet, boggy soils and is commonly grown as a foliage accent in water gardens and pond margins. Although its foliage resembles that of a large iris, sweet flag is actually a member of the acorus family. Insignificant tiny greenish flowers appear in 2-4” long spadixes (without showy spathes), appearing just below the leaf tips in late spring. Flowers give way to tiny fleshy berries. ‘Variegatus’ features variegated leaf blades that are striped with white and green. Foliage and rhizomes are sweetly fragrant when bruised. The species is native to Europe, but has naturalized throughout much of the U. S. and is now found in most counties in the State of Missouri.
No serious insect or disease problems. Scorch will occur if soils are not kept consistently moist to wet.
Mass or specimen for water gardens, stream or pond margins, bogs or in moist open woodland gardens. May also be used in other areas of the landscape, such as low spots, as long as its high soil moisture requirements can be met.