The perennial grass Hierochloe odorata, widely known as sweetgrass, is recognized for its aromatic properties and long history of use in cultural practices, particularly among Indigenous peoples in North America and Eurasia. Often referred to as holy grass or vanilla grass, it has been used for centuries in weaving, as incense, and for various traditional purposes. Identifying sweetgrass requires visual inspection, knowledge of its habitat, and confirmation of its unique fragrance.
Visual Characteristics of Sweetgrass
Sweetgrass is a cool-season perennial that typically grows 12 to 30 inches high, emerging from creeping rhizomes that form thick, matted colonies. The leaves are slender and flat, presenting a bright green to gray-green color on the upper surface. The blades possess a distinctly shiny, glabrous, or hairless underside.
A characteristic feature is the reddish-purple hue often displayed near the base of the plant on the leaf sheaths. Unlike many common grasses, the long leaves are not stiffly upright and tend to arch outward, sometimes reaching lengths of 18 inches or more from the sterile basal shoots. The foliage forms a dense, low-growing mat, which is often easier to spot than the inconspicuous, early-blooming flower stalks.
The Defining Scent Test
The most reliable confirmation of sweetgrass identification comes from its unmistakable scent, present in both fresh and dried foliage. This characteristic aroma is due to coumarin, a naturally occurring chemical compound. Coumarin is responsible for the plant’s vanilla-like fragrance, often described as a mix of warm hay and sweet, freshly cut grass.
To release this definitive scent, one must physically interact with the plant material. This is accomplished by firmly pinching or crushing a small segment of a leaf blade between the fingers. Alternatively, scrape the underside of a leaf to break the plant cells and release the aromatic oil.
Preferred Growing Environment
The geographical range of sweetgrass spans the circumpolar regions of the Northern Hemisphere, including much of northern North America and Eurasia. The plant thrives in environments where the soil remains consistently moist.
Typical habitats include wet meadows, the edges of marshes, riverbanks, and swales. It tolerates a variety of soil types, from loamy to sandy, but consistently requires moisture, as it is not drought-tolerant. Sweetgrass can be found in full sun exposure but also tolerates partial shade conditions.
Differentiating from Common Grasses
Sweetgrass can be visually confused with several other grassy plants. One common look-alike is sweet vernal grass (Anthoxanthum odoratum), which also contains coumarin and shares a similar fragrance. However, sweet vernal grass often has fuzzy, shorter leaves and a more distinct central vein, which sweetgrass typically lacks.
Sweetgrass blades are generally smooth and flat, with a shiny underside, contrasting with the rougher textures of many non-aromatic grasses. A unique distinguishing trait is how the leaves behave when dried: sweetgrass leaves naturally curl into narrow, needle-like threads. Conversely, the leaves of most other grasses, including common meadow grasses, tend to dry and remain relatively flat.