For best results with Panicum virgatum Northwind grasses (Switchgrass), plant them in full sun though they will tolerate partial shade (note that too much shade may cause them to lose their upright nature and they may flop over), in fertile, moist, but well drained soil, though they will tolerate drier soils once established.  Cut back old growth close to ground level in early Spring (use the cuttings on your border as a natural mulch!).
How to grow Panicum virgatum Northwind  
Position: Full sun, partial shade

Foliage: Deciduous, perennial

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

Flowering time: Summer to late Autumn

Growth rate: Moderate/fast

Ultimate height and spread: Height 120cm to 180cm, spread to approximately 75cm

Hardiness: Hardy once established

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