To winter over fountain grass (Pennisetum), start by trimming and pruning it in late winter or early spring to remove dead growth. Apply a layer of mulch around the base, but avoid covering the grass itself. In regions with harsh winters, consider using burlap or breathable fabric for additional protection. Reduce watering during the winter months, allowing the soil to slightly dry between waterings. Inspect the grass for pests and diseases, and address any issues promptly. In the spring, remove winter protection and gradually resume watering to encourage new growth and ensure the grass thrives in the upcoming season.