My garden, alive in my pocket.
Track my garden
🌿

Sweet flag

Acorus calamus · Acoraceae

The gardener's calendar

The right move for September

Ideal time to plant sweet flag: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.

JFMAMJJASOND Planting

ID card

Foliage
Evergreen, light green, linear and fragrant
Flowering
Spring to early summer (May-June)
Adult size
60 to 100 cm in height
Growth
Moderate to fast
Hardiness
Hardy, tolerates down to -15°C
Origin
Wetlands of Asia (China, India, Japan)
Soil type
Moist to marshy, rich in organic matter
Biotope
Palustrine plant of banks and water points

Care

Watering

Sweet flag loves constantly moist or even waterlogged soils. In pots or borders, keep the soil fresh without letting it dry between waterings. In a pond or bog garden, the plant naturally thrives in its aquatic environment. Reduce watering slightly in winter if the plant is potted.

Light Exposure

Position sweet flag in partial shade or dappled light, though it tolerates full sun in cool regions. Overly intense sunlight can dry out the leaves and reduce the intensity of the fragrance. At the edge of a pond or in a bog garden, indirect light is ideal.

Soil and Substrate

Sweet flag thrives in rich, moist, well-decomposed, and slightly acidic soils. Enrich the soil with compost or peat if you cultivate it in a border. In containers, prefer a mix of garden soil, peat, and organic matter that retains moisture well.

Pruning and Maintenance

Sweet flag requires little intervention. Simply remove damaged or yellowing leaves during the season. In late winter or early spring, you can cut back the clump to encourage vigorous growth. Divide the rhizomes every 3 to 4 years to rejuvenate the plant.

Fertilizing

A moderate application of balanced fertilizer in spring is generally sufficient. If the plant is in a pot or in very depleted soil, apply diluted liquid fertilizer once or twice monthly during the growing season. Stop feeding in autumn and winter.

Diseases and Pests

Sweet flag is seldom troubled by diseases if moisture is properly managed. In cases of excessive, poorly-aerated waterlogging, watch for rhizome rot. Pests are rare; only spider mites may appear in very dry conditions. Improve ambient humidity in such cases.

Did you know?

Aromatic sweet flag has been used since antiquity in Asia and India for its medicinal properties: the rhizomes, highly fragrant, contain essential oils and are used in perfumes, incense, and traditional remedies. In medieval Europe, its leaves were scattered on the floors of churches and castles to combat bad odors and purify the air, making it one of the most prestigious plants in ancient phytotherapy.

Where to buy it

Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.

Add this plant to my garden →

Plants from the same family

Browse all plants →

Tips generated and checked by Viridia — adapt them to your local climate.