Sweet Flag

Acorus calamus

Family: Araceae (a-RAY-see-ee) (Info)
Genus: Acorus (AK-or-us) (Info)
Species: calamus (KAL-uh-mus) (Info)


Ornamental Grasses and Bamboo


Ponds and Aquatics

Foliage Color:

Unknown - Tell us

Bloom Characteristics:

Unknown - Tell us

Water Requirements:

Requires consistently moist soil; do not let dry out between waterings

Very high moisture needs; suitable for bogs and water gardens

Where to Grow:

Unknown - Tell us


24-36 in. (60-90 cm)

36-48 in. (90-120 cm)

4-6 ft. (1.2-1.8 m)


24-36 in. (60-90 cm)


USDA Zone 4a: to -34.4 C (-30 F)

USDA Zone 4b: to -31.6 C (-25 F)

USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:

Sun to Partial Shade

Light Shade

Partial to Full Shade


Parts of plant are poisonous if ingested

Bloom Color:

Chartreuse (Yellow-Green)


Bloom Time:

Late Spring/Early Summer


Grown for foliage




Other details:

May be a noxious weed or invasive

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

Patent Information:


Propagation Methods:

By dividing the rootball

By dividing rhizomes, tubers, corms or bulbs (including offsets)

Seed Collecting:

Unblemished fruit must be significantly overripe before harvesting seed; clean and dry seeds

Properly cleaned, seed can be successfully stored


This plant has been said to grow in the following regions:

Birmingham, Alabama

Fort Lauderdale, Florida

Tampa, Florida

New Orleans, Louisiana

Mason, Michigan

Mattawan, Michigan

Minneapolis, Minnesota

Frenchtown, New Jersey

show all

Gardeners' Notes:


On Aug 21, 2015, Ted_B from Birmingham, AL (Zone 8a) wrote:

Lovely bog plant with a storied history of use in medicinal preparations and as a bittering agent in aromatic liqueurs. Germination may require some patience, but is fairly easy in consistently moist peat-based mixes with good lighting.

Keep its feet wet, give it ample sun, and it does the rest.


On Dec 28, 2013, TropicalDaveS from Palm Aire, FL wrote:

My sweet flag has been growing well for over a year in a small pot sitting in a fountain, in partial sun, in Ft. Lauderdale. Snails have managed to feast on it more than once, but not only did it not mind, it barely seemed to notice. I can see that its vigor could be a drawback if not contained, but it is performing well in its setting here.


On Nov 20, 2006, Malus2006 from Coon Rapids, MN (Zone 4a) wrote:

This is a rapid spreading plant. I suspect it have more dry tolerate as a clump grew fine in a small non draining pot put in the ground and get no extra water. Seem to have some shade tolerance. Nice to use in a pot in the pond but need to be cut every three years as it will overcrowd the pots and spread their rhizomes some distance beyond the pot.

Extra info May 2, 2008: I have success growing it as a cattail - like plant in woodland shade in a stream. It is smaller in woodland shade but more tame.


On Nov 16, 2006, frostweed from Josephine, Arlington, TX (Zone 8a) wrote:

Sweet Flag, Acorus calamus, is native to Texas and other States.


On May 5, 2006, tyler70006 from New Orleans, LA wrote:

This is the plant that Walt Whitman was referring to in his collection of poems "Leaves of Grass". He enjoyed eating the rhysome of the plant and it was said to be energizing. It was known as an american indian medicinal plant.

Leaves of Grass! The largest leaves of grass known! Calamus! Yes, that is Calamus! Profuse, rich, noble, upright, emotional!"


On Apr 7, 2005, melody from Benton, KY (Zone 7a) wrote:

Information only, I do not grow this plant.

This plant grows in water and boggy, wet soils and has iris-like leaves. The flower cluster is an outward jutting finger shaped cluster of brownish-green. The fruit is a small berry with a gelatin-like texture.

Common along swamps, marshes, riverbanks, meadows and small streams throughout the east. The only places it can't be found is Florida and the Arctic.

The thick rhizomes were sometimes candied and this old-fashioned confection is called calamus. It has a distinctive odor and flavor.