When to plant - Grasses can be planted in the fall or spring, but spring is preferable. Spring planting allows the grass to develop a solid root system before the winter frost. If you do choose to plant in fall, do so early in the season, and cover the base of the grasses with hay or straw before the first frost hits.
Preparing the soil - Choosing a well-drained area is of utmost importance when planting ornamental grasses. Till the planting area well, and add organic material to the soil to promote drainage. Remember that most ornamental grass grows tall, so provide ample space for the foliage. Pampas Grass grows particularly wide, so be sure to consider the possible width of the plants.
Transplanting from the pot - When planting ornamental and garden grasses, dig just deep enough for the crown of the plant to be level with the soil’s surface. The foliage of grasses planted too deeply may rot in the ground. When transplanting from a pot, add water and compost to the hole and score the root ball before planting the grass. After planting, water well.
Watering - Ornamental grasses should be very well watered during the first growing season; liberal watering helps the root system develop. Established plants need only supplemental watering.
Fertilizing - Ornamental grasses don't require much fertilizer. Too much fertilizer can push up nitrogen levels, causing the blades to droop or flop over. Fertilize minimally, using a low-nitrate product.
Cutting and Cleanup - The foliage of ornamental grasses help to insulate them through the winter, so wait until spring to prune. For most spring grasses, cutting back 4 to 6 inches of dead growth before the growing season begins helps the plant "warm up" and begin growing earlier.