For best results with Panicum virgatum Thundercloud grasses (Switchgrass), plant them in full sun, in fertile, moist, but well drained soil, though they will tolerate drier soils once established.  Cut back old growth close to ground level in late Winter or early Spring (use the cuttings on your border as a natural mulch!).
How to grow Panicum virgatum Thundercloud  
Position: Full sun

Foliage: Deciduous, perennial

Soil and site: Best in moist, fertile, well-drained soil

Flowering time: Late Summer to Autumn

Growth rate: Moderate/fast

Ultimate height and spread: Height to 200cm, spread to approximately 100cm

Hardiness: Hardy

Aftercare: Cut back old dead growth close to ground level in late Winter or early Spring.