perennial

Japanese Sweet Flag

Acorus gramineus 'Yodonoyuki'

Not currently listed at our partner nurseries.

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Essentials

At a Glance

Plant Type

Perennial

Height

10 inches

Width

12 inches

Light

Full Sun, Partial Sun

Zones

5, 6, 7, 8, 9

Water

Moist to wet

Humidity

Prefers humid environments

Lifespan

Perennial

Native To

Asia

Toxicity

Low toxicity; may cause stomach upset if ingested.

The Story

Plant Bio

Acorus gramineus, commonly known as Japanese sweet flag, is a semi-evergreen, grass-like perennial that forms a low-spreading clump of narrow, iris-like, green leaves. It thrives in wet, boggy soils and produces tiny, inconspicuous, yellowish-green flowers in late spring to early summer. The cultivar 'Yodonoyuki' is prized for its striking variegated foliage. New leaves emerge with a pink flush, maturing to display creamy-white stripes on a green background, creating a bright, fine-textured effect in moist garden settings.

Uses & Benefits:

Adds lush, grassy texture to shaded gardens, providing year-round greenery.

Tolerant of wet soils, ideal for water features and damp areas.

Provides habitat for beneficial insects and small birds.

Marketplace

Where to Buy

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Planting

How to Grow

Tuck rhizomes into moist soil in early spring
Water regularly to keep soil moist for 6 weeks
Mulch to retain soil moisture and suppress weeds
Divide clumps every 2-3 years in spring or fall
Prune back dead foliage in late winter
Place in partial shade for best growth

Pro Tip

Ensure soil remains consistently moist for optimal growth.

Keep It Thriving

Care Guide

Do

Water regularly to keep soil moist
Mulch to conserve moisture
Divide clumps every few years
Prune dead foliage in winter

Don't

Avoid drought conditions 🌱
Don’t let soil dry out completely ❌
Avoid heavy, waterlogged soil without drainage
Refrain from excessive fertilizing

Seasonal Care Calendar

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

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Shaded borderMoist area accentWater garden edge

Companion Plants

Hosta Ferns Ligularia Japanese Iris

Multiply

Propagation Methods

Good to Know

Common Questions

Japanese Sweet Flag questions

What zones can Japanese Sweet Flag grow in?

Japanese Sweet Flag is hardy in USDA Zones 5–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is Japanese Sweet Flag deer resistant?

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

When does Japanese Sweet Flag bloom?

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

Does Japanese Sweet Flag need full sun?

Japanese Sweet Flag does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.