Purple fountain grass (Pennisetum setaceum Rubrum), an herbaceous ornamental grass native to east Africa and southwest Asia, produces graceful arches of reddish-purple foliage and tall plumes of pinkish-purple flowers in summer and fall. Grown as a perennial in USDA hardiness zones 8 through 11, purple fountain grass cannot tolerate cold temperatures and performs as an annual in cooler zones. The plant resists drought and grows quickly, making it ideal for placement in rock gardens and annual beds. Planted in large groups, purple fountain grass produces a dramatic effect when the wind swirls the iridescent foliage.
Plant purple fountain grass any time of year once the soil has warmed to a workable temperature. Spring plantings yield the best results, however. Plant in an area that receives full sun and has well-drained, fertile soil.
Dig a hole in the soil about twice as wide as the plant's roots and of equal depth. Insert the roots into the hole, spread them out evenly and cover with soil. Water just after planting to stimulate new growth. Space purple fountain grass plants 36 to 60 inches apart.
Water purple fountain grass once every seven days to prevent the soil from drying out completely. Reduce the watering frequency to once every 10 to 14 days during the plant's winter dormancy period. Soak the soil to a depth of about 8 inches each time to ensure the roots receive adequate moisture.
Feed the plant once per year during early spring using a slow-release 10-10-10 NPK fertilizer. Read the directions on the label for the proper dosage and application procedure. Water lightly before and after applying to dissolve the nutrients into the soil and prevent burning the plant's roots.
Cut purple fountain grass back during late winter or early spring just before the plant begins growing actively again. Remove some flowers after they fade to encourage reblooming. Allow some blooms to remain and turn to seed heads for self-propagation and ornamental appeal.