Sweet flag (Acorus calamus)

Also known as: Muskrat Root, Bitter Pepper Root, Myrtle Flag, Myrtle Root, Pine Root, Sweet Cane, Sweet Grass, Sweet Root, Flag root, Calamus root

Sweet flag (Acorus calamus) is a perennial grass that will grow from 61 to 91 cm tall and 46 to 61 cm wide. It spreads by rhizomes and grows slowly to form a dense ground cover. It thrives in full sun or partial shade and is not invasive. The foliage has a sweet fragrance and in late spring blooms small yellow-green flowers followed by tiny red berries that ripen in fall.

In This Article

Care Tips Water Sunlight Temperature Soil Fertilize Prune Propagation Repotting Toxicity

Attributes of Sweet flag

Lifespan

Perennial

Plant Type

Herb

Plant Height

2 m

Spread

45 cm to 60 cm

Leaf Color

Green Blue White Variegated

Flower Size

3 mm to 4 mm

Flower Color

Green Yellow White

Images of Sweet flag

Quickly Identify Sweet flag

Fragrant lance-shaped leaves, bright green, reaching 4 feet (120 cm).

Modest greenish flowers in compact clusters with 6 tepals and stamens.

Inconspicuous berry-like fruit, spongy texture, greenish-yellow, within inflorescence.

Sword-shaped aromatic leaves with wavy margin, red base, and sweet fragrance when crushed.

Thick, fleshy rhizome with cylindrical yellowish-brown stems, supporting upright growth.

Scientific Classification of Sweet flag

Phylum

Vascular plants

Class

Monocotyledons

Order

Acorales

Family

Calamus

Genus

Calamus

Species

Sweet flag

Planting and Growing of Sweet flag

Care Difficulty

Easy

Watering Schedule

Every 8 days

Sunlight Requirements

Partial sun

Sunshine Duration

6-10 hours

Ideal Temperature

60-77℉

Soil Type

Potting Mix, Peat Mix

Soil pH

6.5-7.5

Fertilizer Type

Balanced

Pruning Season

Spring, Summer

Pruning Area

Branches, Leaves

Pruning Frequency

2 times a year

Repotting Season

Spring

Pot Type

Plastic, Ceramic

How to Water Sweet flag?

For Acorus calamus, watering should be done thoroughly but not excessively. The aim is to soak the soil until water begins to drain from the pot's base. This ensures the entire root system is hydrated without waterlogging it.

What are the symptoms of an underwatered Sweet flag? ›

What should I do if my Sweet flag is not getting enough water? ›

What are the symptoms of an overwatered Sweet flag? ›

How to save an overwatered Sweet flag? ›

What Are the Sunlight Requirements for Sweet flag?

Sunlight Requirements: Partial sun, Full sun

Duration of light: 4 to 6 hours

Partial sun to full sun ensures optimal growth, promoting vibrant leaf colors and healthy overall development. It balances light intensity to support both leaf and root vigor.

What kind of light does Acorus calamus thrive in? ›

How can I achieve the best lighting for Acorus calamus? ›

What benefits does Acorus calamus gain from ideal lighting conditions? ›

What Is the Ideal Temperature Range for Sweet flag?

Ideal Temperature: 60 ~ 77℉

For Acorus calamus cultivation, maintaining an ideal temperature range between 60°F and 77°F is crucial. This range supports optimal metabolic processes and growth, ensuring the plant remains healthy and exhibits vibrant foliage. Ensuring consistent temperatures within this range helps avoid stress-induced growth interruptions.

What Soil is Best for Sweet flag?

Soil type: Loam, Sandy loam, Peat soil

Soil PH: 6.5 ~ 7.5

Acorus calamus thrives in moisture-retentive soil, ensuring its roots are consistently hydrated. Such soil prevents drying out and supports healthy growth and vibrant foliage. The plant benefits from a nutrient-rich soil composition that supplies essential minerals and nutrients, promoting robust growth and a resilient structure. High organic matter in soil supports healthy microbial activity which aids in nutrient uptake and improves soil aeration, vital for the well-being of Acorus calamus.

How to Fertilize Sweet flag?

Fertilizer type: Balanced

Acorus calamus, also known as sweet flag, is not a heavy feeder. Apply liquid fertilizer diluted to half strength, about 2 tablespoons per gallon of water, every time you fertilize. For slow-release fertilizer, use approximately 1 tablespoon per plant, distributed evenly around the base.

How to Prune Sweet flag?

Pruning Time: Spring, Summer, Autumn, Winter

Start by sterilizing your pruning shears to prevent the spread of disease. Remove any yellow or brown leaves by cutting as close to the base as possible. Trim away any flower spikes after blooming to encourage new growth. Make sure to cut at a slight angle to prevent water from collecting on the cut surfaces.

How to Propagate Sweet flag plant?

Propagate Time: Spring, Early spring, Late spring

Begin by preparing a well-draining soil mix. Acorus calamus prefers moist soils, so ensure that the soil retains some moisture without becoming waterlogged.

Spread the seeds evenly over the prepared soil. Lightly cover them with a thin layer of soil or compost, and gently water to avoid disturbing the seeds.

For division propagation, carefully dig up the mature plant and cut the rhizomes into sections, ensuring each section has roots and shoots. Replant immediately to prevent drying out.

How to Repot Sweet flag plant?

Repotting frequency: Every 2-3 years

Acorus calamus should be repotted when you notice it becoming root-bound, which can be identified by roots creeping out of the drainage holes, or if growth is stagnating despite optimal conditions. Repotting in spring or autumn allows the plant to settle before peak growing conditions.

Choose a pot that is just one size larger than the current one and made of material like ceramic or plastic to retain moisture. Ensure it has drainage holes to prevent waterlogging, which can severely impact the roots.

Opt for a soil rich in organic matter with good moisture retention, yet well-draining, like a mix of peat, bark, and perlite. This ensures the roots receive the necessary nutrients and aeration, promoting healthy growth.

Toxicity of Sweet flag

Is Sweet flag toxic to humans?

Sweet flag is classified as a mildly toxic plant, containing trace amounts of alkylbenzenes—known carcinogens—that could potentially lead to certain types of cancer when consumed in substantial quantities. Although the risk of toxicity is minimal due to these small quantities, the plant's leaves, stem, and flowers harbor additional toxins that can provoke skin irritation in sensitive individuals. Common reactions include rashes, redness, and swelling. If ingested, more serious symptoms may arise, such as nausea, vomiting, and abdominal pain. Furthermore, high consumption of the plant's matter can act as a depressant on the central nervous system. Those who are on monoamine oxidase inhibitors are particularly vulnerable to experiencing severe side effects.

WARNING

The judgment on toxicity and danger is for reference only. We DO NOT GUARANTEE any accuracy of such judgment. Therefore, you SHALL NOT rely on such judgment. It is IMPORTANT TO SEEK PROFESSIONAL ADVICE in advance when necessary.