Sweetgrass (Hierochloe odorata) is a highly aromatic perennial grass, prized in landscaping for its slender, glossy foliage and distinctive scent. The sweet, vanilla-like fragrance comes from the compound coumarin, which becomes more pronounced when the grass is dried or crushed. This cool-season grass, native to both North America and Eurasia, brings a unique sensory appeal to garden design.
Site Selection and Planting Techniques
Sweetgrass establishes best in full sun but tolerates partial shade in hotter climates. It requires consistently wet to moist soil conditions to thrive, mimicking its natural habitat in meadows and along waterways. The site should ideally feature rich, loamy soil.
Before planting, enrich the area by incorporating organic material like compost to help retain moisture and improve soil structure. Sweetgrass prefers a soil pH that is slightly acidic to neutral (6.0 to 8.0). Since propagation from seed is difficult due to low germination rates, acquire nursery-grown transplants or divisions.
Planting should occur in the spring to allow the grass a full season to establish its root system. When using divisions, ensure each piece includes a portion of the rhizome and a few shoots. Plant these divisions at the same depth they were previously, spacing them two to three feet apart.
Immediately after planting, water the area thoroughly to settle the soil and eliminate air pockets. Cutting the newly transplanted foliage back to three or four inches encourages the plant to focus its energy on developing a strong root system.
Ongoing Cultivation and Management
Consistent moisture is the most important factor for the long-term health of Sweetgrass; the soil should never be allowed to dry out completely. If the site does not naturally retain water, a regular watering schedule is necessary during dry periods. Fertilization needs are minimal, and nitrogen application should be avoided in the first year to prevent weed competition.
The most important management consideration is controlling its aggressive spread. Sweetgrass is a vigorous perennial that expands rapidly via underground rhizomes, sometimes spreading up to two feet annually. If left unchecked, it can quickly colonize an entire garden bed, making containment a top priority.
To prevent unwanted encroachment, install a root barrier extending eight to twelve inches deep into the soil. This barrier should also stand an inch or two above the soil line to block surface runners. An effective alternative is to plant Sweetgrass in a large container sunk into the ground, which completely restricts the rhizomes.
Foliage can be harvested once or twice a year when the leaves reach their mature length of twelve to twenty-four inches. Harvesting is best done in late summer by carefully cutting the stems without damaging the crown. This practice provides aromatic material, rejuvenates the plant, and prevents the foliage from flopping over.
Landscape Design Applications
Sweetgrass’s upright, bright green foliage provides a fine texture that contrasts well with broader-leaved perennials and shrubs. Mass planting creates a lush, meadow-like effect, which is effective in naturalized garden sections or along the edges of ponds and streams.
The grass’s strong, mat-forming rhizomes make it an excellent choice for functional uses, such as erosion control on moderately sloped banks or moist hillsides. In these areas, its aggressive spreading habit is an asset, stabilizing the soil where other plants might struggle. However, this application requires careful planning to ensure the grass remains confined to the desired slope.
To maximize the enjoyment of its characteristic scent, Sweetgrass should be placed near high-traffic areas. Planting it along a walkway, patio, or seating area allows the vanilla fragrance to be released when the foliage is disturbed. For smaller spaces, container gardening is the ideal solution, providing mobility and absolute control over its spread.
Sweetgrass pairs well with companion plants that tolerate similar wet or moist soil conditions and complement its texture. Suitable partners include tall, moisture-loving perennials like sneezeweed and coneflowers. These provide a vertical contrast to the grass’s more relaxed, arching form.