Sweet Flag (Acorus calamus)
[ah-KOR-us KAL-ah-mus]

Deciduous Perennial in the Acoraceae Family
 
Buy Sweet Flag
Size Notes Price Availability
Tray of 10 4" pots Field $62.78

An aromatic wetland perennial with iris-like, sword-shaped leaves that release a sweet, spicy scent when crushed. Thrives in pond margins, bogs, and consistently moist soil, spreading gradually by rhizome into naturalized colonies.

Acorus calamus is a wetland perennial in the sweet flag family (Acoraceae), grown for its narrow, iris-like leaves and pleasantly aromatic rhizomes rather than for its flowers, which are small, greenish-yellow, and easy to miss. The leaves are flat, sword-shaped, and slightly wavy along one edge, often tinged reddish at the base, and release a sweet, spicy fragrance when bruised or crushed.

Native across wetlands of the Northern Hemisphere, sweet flag naturalizes readily by creeping rhizomes to form dense colonies at the water's edge. Plants sold in North American nurseries are typically a sterile triploid form that does not set viable seed, so spread happens only vegetatively, by rhizome growth or division — a useful trait for gardeners who want the colonizing habit without unwanted seedlings.

Note: the fresh rhizome has a history of medicinal and flavoring use, but some populations contain beta-asarone, a compound the FDA restricted from food use in 1968; the fresh root should not be eaten or used medicinally without expert guidance.

Pros

  • Thrives in boggy, pond-edge, and rain garden conditions most perennials can't tolerate
  • Aromatic, iris-like foliage releases a sweet fragrance when crushed
  • Low-maintenance once sited correctly, with no serious pest or disease problems
  • Spreads reliably by rhizome to fill in wet, low-lying areas

Cons

  • Needs consistently moist to wet soil; leaf tips scorch if it dries out
  • Spreads by rhizome and can form large colonies if not contained
  • Fresh rhizome is not safe to eat or use medicinally without guidance
Why Like In the wild, sweet flag forms dense colonies along the quiet edges of ponds, marshes, and slow streams, where its narrow, upright leaves create texture among cattails and sedges. Muskrats feed on its rhizomes, and the plant hosts a specialist leaf beetle (Plateumaris shoemakeri) found almost nowhere else. Crushing a leaf releases its trademark sweet, spicy fragrance — a good field-identification trick along a wetland edge.
Highlights A wetland accent plant valued for its aromatic, iris-like foliage and easy-care colonizing habit at the water's edge.
 

Plant Data

Mature Size 24 - 30 inches tall. 18 - 24 inches wide.
Growth Rate Medium
Sun Exposure Partial Shade - Full Sun
Moisture Tolerance Medium - Wet: Tolerates shallow standing water and consistently saturated soil; will scorch if allowed to dry out.
Zones 4a - 10b (Usually hardy to -30° F)
Tags Attracts Wildlife, Deciduous, Deer Resistant, Full Sun, Grasses, Grown For Attractive Foliage, Medium, Native to Asia, Partial Shade, Partial Sun, Perennial, Potentially Toxic, Rabbit Resistant, Tolerant of Acidic Soil, Tolerant of Clay Soil, Tolerant of Loamy Soil, Tolerant of Moist Soil, Tolerant of Sandy Soil, Wet, Wet Site Tolerant
Bloom Period Late Spring to Early Summer
Flower Color Greenish-Yellow (Inconspicuous)
 

In The News
 

More Info from Experts

Commonly Planted with...

Pairs naturally with other pond-edge and bog perennials such as blue flag iris (Iris versicolor), pickerelweed (Pontederia cordata), marsh marigold (Caltha palustris), and cardinal flower (Lobelia cardinalis), all of which share its tolerance for consistently wet soil.
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Pricing and Availability History

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Past Availability
2025 : 07/27 - 10/04
2024 : 08/15 - 09/08
2023 : 08/24 - 08/27


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Field-Grown vs. Greenhouse-Grown Plants

Plants which are well-adapted to our local climate are most often field-grown (outside). Field-grown plants are generally cheaper and have the advantage of already somewhat acclimated to our cold winters, but that means they’re not artificially far along in the spring and tend to bloom at the normal time in our area.

Spring annuals and tender perennials are typically grown in Greenhouses so they can be ready and luxurious exactly when customers want them. Some perennials are also “forced” into early bloom in greenhouses. In May, there can be a very big difference between field-grown and greenhouse-grown plants of the same type. The latter typically look good right away (so they’re a great choice where that’s important), but we typically pay a premium for it.


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No Pricing or Availability Right Now

We order from a rotating cast of the best nurseries in the Great Lakes region. It looks like we've offered this plant in the past, but the nurseries we're working with this week don't appear to have it in stock at the moment.

Our goal is to bring as many plants together under "one roof" as possible, so we'll try hard to make it available again in the future!