Sweet Grass, scientifically known as Hierochloe odorata or Anthoxanthum nitens, is a perennial grass known for its distinctive, vanilla-like aroma. Its name translates from Greek as “holy grass,” reflecting its deep cultural significance, particularly among Indigenous peoples of North America and Eurasia. It has been used for centuries in ceremonies, woven into baskets, and burned as a smudge for purification due to its strong, sweet scent.
Growth Habit and Leaf Structure
Sweet Grass is a cool-season perennial that typically forms loose clumps, growing to a height of 10 to 24 inches. The plant spreads aggressively through long, creeping, white underground stems called rhizomes, which can expand the plant’s footprint by up to two feet annually. This rhizomatous growth allows it to form dense mats of foliage over time. The stems themselves are hollow and hairless, with open sheaths that encase the base of the leaves.
The leaves are long, flat blades, ranging from 4 to nearly 12 inches in length. They are generally hairless, or glabrous, and a bright to gray-green color. A noticeable feature is the difference in sheen between the leaf surfaces, with the upper side often appearing duller and the lower side having a more reflective, shiny appearance. The leaves that emerge directly from the base are the longest and hold the majority of the plant’s characteristic fragrance.
Distinctive Floral Characteristics
The flowering parts of Sweet Grass appear later in the spring and early summer, typically between May and July, which is earlier than many other grasses. The flowers develop on separate, taller stems that can rise to two feet or more above the vegetative foliage. These flowering stalks, unlike the leaves, do not possess the strong, sweet scent.
The inflorescence is an open, pyramidal cluster called a panicle, which is relatively short, usually measuring between 1.6 to 3.5 inches long. The small flower clusters, or spikelets, are comprised of three florets and are often a greenish-purple or bronze color. These spikelets are arranged on slender, widely spreading branches, which may droop slightly, giving the flower head a loose, airy appearance. The presence of these bronze-tinted panicles is a key visual marker for identification during the reproductive season.
Identification Through Scent and Texture
The most reliable feature for identifying Sweet Grass is its aroma, which is often described as a blend of vanilla and warm hay. This fragrance is caused by the presence of a chemical compound called coumarin, which is found in the plant’s leaves. The scent is faint in the fresh, green plant, but it becomes significantly more pronounced and sweet when the leaves are dried, crushed, or bruised.
When handled, the leaves can feel relatively tough or stiff, especially after they have been harvested and dried. The lower part of the stem, near the roots, may exhibit a reddish-purple tint, which is a useful visual cue. The concentration of coumarin is highest in the vegetative leaves, making the scent the definitive way to distinguish this species from other, visually similar grasses.
Common Habitats and Range
Sweet Grass has a wide native range that spans across northern Eurasia and a large portion of North America, extending from Labrador to Alaska and south into states like New Jersey, Iowa, and Arizona. It is classified as a cool-season grass, favoring environments with consistent moisture. The plant is most commonly found in moist meadows, low prairies, and along the edges of sloughs, marshes, and riverbanks.
It thrives in soils that are consistently wet but well-drained, often in areas with partial sun to full sun exposure. The natural habitat includes sites with rich, organic soil, such as freshwater wetlands and riparian zones. The plant’s preference for moist, cool conditions is a limiting factor in its distribution, but its presence in these specific environmental niches helps narrow down the search for it in the wild.