Glyceria occidentalis, commonly known as Northwestern Mannagrass or Western Mannagrass, is a perennial grass native to wetlands, riparian zones, and moist meadows in the Northwestern US and Southwestern Canada. It thrives in these habitats, often on clay or loamy soils, and is adapted to areas with seasonal flooding or consistent moisture. This grass typically grows at a moderate rate to a height of 1-3 feet (0.3-0.9 meters), with a similar spread. It forms dense tufts of bright green, glossy leaves that can add texture to garden settings. The flowers are green and inconspicuous, appearing in the summer, but they provide important habitat and food for wildlife.

Northwestern Mannagrass is valued for its ability to stabilize soil and for its use in water gardens, rain gardens, and other moisture-rich environments. It is also useful for erosion control along stream banks and in naturalized areas. In cultivation, it requires full sun to part shade and prefers medium to high amounts of water, thriving in medium or slow-draining clay or loam soils. While it is not known for showy flowers, its foliage remains attractive throughout the growing season. Care should be taken as it can spread vigorously in ideal conditions, potentially becoming invasive in some areas.CC BY-SA 4.0