Species

Acorus gramineusJapanese Sweet Flag

8 other cultivars

groundcover

Masamune Japanese Sweet Flag

Acorus gramineus 'Masamune'

The Story

Plant Bio

Acorus gramineus 'Masamune' is a dense, grass-like perennial with narrow, upright foliage and small, inconspicuous flowers that blend seamlessly with its lush, green clumps.

This cultivar is distinguished by its striking, upright fans of bright golden-yellow, grass-like foliage, adding a decorative touch to water gardens and borders.

Uses & Benefits:

Provides lush, evergreen foliage that adds texture and color to shaded garden areas.

Tolerant of wet soils, making it ideal for water gardens and rain gardens.

Supports local biodiversity by providing habitat in shaded, moist environments.

SpeciesAcorus gramineusJapanese Sweet Flag

Essentials

At a Glance

Plant Type

Groundcover

Height

8 inches

Width

12 inches

Light

Partial Sun, Shade

Zones

5, 6, 7, 8, 9

Water

Moist to wet

Humidity

High

Lifespan

Perennial

Native To

Japan

Toxicity

Non-toxic

Bloom period

Early spring – Late fall

In flower about 9 months of the year

Planting

How to Grow

Tuck rhizomes 2 inches deep in moist soil.
Water regularly to keep soil consistently damp.
Mist foliage during dry spells for health.
Place in shaded or partially sunny locations.
Mulch to retain soil moisture and suppress weeds.
Divide every 3-4 years for vigorous growth.

Pro Tip

Use in shaded areas with moist, well-drained soil for best results.

Keep It Thriving

Care Guide

Do

Maintain consistent moisture 🌱
Mulch to conserve soil humidity
Divide every 3-4 years

Don't

Allow soil to dry out completely ❌
Expose to full sun in dry conditions ❌
Overcrowd plants

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Divide
Spring Cleanup

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Shaded water garden borderMoist woodland garden accent

Companion Plants

Hostas Ferns Astilbe LigulariaJapanese Iris

Multiply

Propagation Methods

Good to Know

Common Questions

Masamune Japanese Sweet Flag questions

What zones can Masamune Japanese Sweet Flag grow in?

Masamune Japanese Sweet Flag is hardy in USDA Zones 5–9. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is Masamune Japanese Sweet Flag deer resistant?

Yes — Masamune Japanese Sweet Flag is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.

When does Masamune Japanese Sweet Flag bloom?

Masamune Japanese Sweet Flag typically blooms in early spring through late fall. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Masamune Japanese Sweet Flag need full sun?

Masamune Japanese Sweet Flag does best in part shade.