Essentials
At a Glance
Plant Type
Perennial
Height
30 inches
Width
36 inches
Light
Full Sun, Partial Sun, Shade
Zones
4, 5, 6, 7, 8, 9
Water
Requires consistently moist soil or water
Humidity
Prefers high humidity
Lifespan
Perennial
Native To
Asia, Europe, North America
Toxicity
Toxic; contains carcinogenic compounds
The Story
Plant Bio
Acorus calamus, commonly known as sweet flag, is a perennial aquatic plant with grass-like, aromatic foliage and upright, spiked flowers that are greenish-yellow in color. This species is valued for its fragrant rhizomes used in traditional medicine and as a flavoring, and it thrives in wet, marshy environments.
Bloom Period:
Uses & Benefits:
Marketplace
Where to Buy
Shipping costs Year-round shipping Free shipping
Planting
How to Grow
- Tuck rhizomes into moist soil in early spring
- Water regularly to keep soil damp
- Mulch around plants to retain moisture
- Divide clumps every 3–4 years in early spring
- Fertilize with a balanced aquatic plant fertilizer in spring
- Monitor for pests and remove affected leaves
Pro Tip
Keep soil consistently moist for best growth
Keep It Thriving
Care Guide
Do
- Water regularly to maintain moist soil 🌱
- Mulch to retain soil moisture
- Divide clumps every few years
Don't
- Allow soil to dry out completely ❌
- Use chemical fertilizers excessively ❌
- Neglect dividing or pruning
Seasonal Care Calendar
| Task | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Divide | ||||||||||||
| Plant | ||||||||||||
| Prune |
Watch Out For
Pests & Diseases
Common Pests
Common Diseases
In the Garden
Landscape Uses & Companions
Landscape Uses
Companion Plants
Multiply
Propagation Methods
Good to Know
Common Questions
Sweet Flag questions
What zones can Sweet Flag grow in?
Sweet Flag is hardy in USDA Zones 4–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.
Is Sweet Flag deer resistant?
Yes — Sweet Flag is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.
When does Sweet Flag bloom?
Sweet Flag typically blooms in early summer through late summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.
Does Sweet Flag need full sun?
Sweet Flag does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.
More Acorus to compare
Golden Japanese Sweet Flag
Acorus gramineus 'Wogon'
Variegated Sweet Flag
Acorus calamus 'Golden Variegated'
Licorice Japanese Sweet Flag
Acorus gramineus 'Licorice'
Variegated Japanese Sweet Flag
Acorus gramineus 'Hakuro Nishiki'
Dwarf Sweet Flag
Acorus gramineus 'Pusillus'
Variegated Sweet Flag
Acorus calamus 'Variegatus'
Keep exploring
Explore the genus
Collections featuring this plant
Grow Sweet Flag with confidence
See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.
