Purple fountain grass (Pennisetum setaceum), or tender fountain grass, serves as a popular ornamental grass. The deep purple foliage and feathery flower spike withstand drought and persist until frost. Purple fountain grass requires little maintenance and makes a bold statement as a specimen or when paired with companion plants, especially those with yellow foliage. Purple fountain grass grows as an annual throughout most of the United States, except in southern landscapes, where it grows as a perennial.
Purple fountain grass typically grows 3 to 4 feet tall and 2 to 4 feet wide, according to the University of Florida IFAS Extension. The grass emerges in mounds and develops a fountain habit. The hollow stalk yields 12-inch pinkish-purple flower plumes throughout the summer until late fall, when the foliage turns an amber color. The flower heads tend to nod with the slightest breeze
Though only a medium-sized grass, purple fountain grass helps define areas within a landscape. The grass adds vertical height to the garden, and so makes an ideal plant at the back of a mixed border among shrubs or herbaceous perennials and annuals. The fountain effect of the foliage softens lines between lawns and walkways. Purple fountain grass works well in mass plantings in foundation schemes, public gardens and roadway medians.
The Rubrum cultivar, also known as Cupreum and Atrosanguineum, features dark purplish-red plumes and leaves. The Eaton Canyon cultivar looks like Rubrum, but it has finer foliage and only grows 30 inches tall, so it is better suited as a container garden plant. The Burgundy Giant cultivar is not as popular as Rubrum or Eaton Canyon, but it develops large flowers and a deep burgundy color.
Purple fountain grass develops deeper color in full sun and tends to lean over when planted in shade. The plant adapts to a wide variety of soils, but performs best in moist, well-drained soil. Taller varieties may require staking in wet soils. Established plants require little more than an inch of deep watering per week.
The Rubrum cultivar remains sterile, but other cultivars set vast quantities of seed. The seed forms nearby plantlets or spreads to other parts of the landscape, which makes the grass invasive. Prune fountain grass by cutting the plant to the ground in fall. Old plants tend to look unkempt and develop thatch. Raking through the mound removes dead leaves.