Purple Fountain Grass Plant Profile

Purple fountain grass in bloom with lavender flowers in background.
David Beaulieu

Purple fountain grass—named for the arcing spikes of purplish flowers that gracefully spray out of its mass of long, slender, burgundy-colored leaves—is not a very cold-hardy plant, but it is well worth growing in the north—even if you can enjoy it for only two seasons out of the year. It is more expensive than other plants grown as annuals but this plant will delight you with a showy, multi-faceted display. A clump-forming ornamental grass variety, it is a tropical plant.as well as a deer-resistant ornamental grass and not an invasive plant.

  • Botanical NamePennisetum setaceum Rubrum
  • Common Name: Purple fountain grass or red fountain grass
  • Plant TypeAnnual in cold climates
  • Mature Size: Height of 3 to 5 feet with a spread of 2 to 4 feet
  • Sun Exposure: Full sun
  • Soil Type: Most types of well-drained soil
  • Soil pHAcidic to neutral
  • Bloom Time: July
  • Flower Color: Purple
  • Hardiness Zones: 9, 10
  • Native Area: Africa and southern Asia
Purple Fountain Grass - Pennisetum Setaceum 'rubrum'
 

How to Grow Purple Fountain Grass

Although it can be planted nearly anytime, spring is the most suitable time for planting. These plants need a sunny location with well-draining soil. Since mature plants can reach about 5 feet tall and just as wide, they should be given plenty of room in the garden with at least 3 feet in between. Dig a hole both deep and wide enough to accommodate the roots and then water your purple fountain grass thoroughly.

Light

The grass will tolerate some light shade though it enjoys the full sunlight. Look for an area in your garden that receives full sun, as the plant prefers warmer conditions.

Soil

Purple fountain grasses can do well in many types of soil as long as it is well draining. Preferred soil is loamy soil.

Water

Purple fountain grass is considered a drought-tolerant ornamental grass. Water once or twice a week until plants are established. Give time for the soil to dry to the touch between each watering. In areas that receive rain occasionally, you will not need to water the grass once it has been established. If you are cursed with a soil that is somewhat waterlogged, try a sedge grass instead.

Temperature and Humidity

Purple fountain grass is best grown in hardiness zones 9 to 10. If your winter temperatures remain above 20 degrees Fahrenheit, then purple fountain grass can be grown as a perennial and cut back in early spring. New growth will initiate as the temperatures climb.

Those in colder zones will have to make do with enjoying its vivid color and striking, vase-shaped form in summer and fall unless you do not mind going through the trouble of overwintering it indoors.

Fertilizer

Fountain grass is hardy and grows in poor soil, but fertilizer will boost its growth. The grass will need additional nutrients when flowering. During that time (generally, the summer), use a general-purpose, slow-release fertilizer.

Propagating Purple Waffle Plants

Purple fountain grass can be propagated through seed or division. Division is a faster and more reliable form of propagation.

  • Seeds: This grass produces flowering stems, which are full of feathery seeds. Collect seeds when they are dry, usually in fall. Take the whole stem and allow the flower stalk to dry in a cool, dry place. Surface sow in good potting soil with just a dusting of sand on top. Water until the container is evenly moist and then place in a plastic bag or top with a plastic dome. Once you have seedlings with two sets of true leaves, transplant them to larger pots. Harden them off in spring and install in prepared containers or beds.
  • Division: Dig up the plant when it is going dormant and cut it into two or more sections with healthy roots and leaves. Use very clean, sharp implements to make your cuts and discard any rotten or dead plant matter and roots. Replant immediately and keep moist as the disturbed piece settles into its new home.

Growing in Containers

Since this plant cannot tolerate winter well, it is a good specimen for growing in containers. You will need to bring it in for the winter.

If you choose to overwinter the plant, you have two options: Treat it as a houseplant and put it in a relatively cool room in your home with sun exposure or store it in a cool (but not freezing) location such as a cellar. Water sparingly, but do not let the soil in the container totally dry out. You can return it to the outdoors next spring.

Landscaping

The beauty of purple fountain grass makes it popular as a focal point in a mixed planting, often in container gardens. But people will also mass several of the plants together (in a border planting, for example). These can stand alone as specimen plants. Some like to use them to jazz up a foundation bed for the summer. Grouped with plants of a coarser texture, they can create a striking contrast.

Because the autumn seed heads of this plant are so attractive, purple fountain grass, like maiden grass, is very useful in fall flower gardens. The feathery seed heads (or "plumes") can later be cut for dried flower arrangements.

Purple fountain grass also looks wonderful with contrasting yellow flowers. You can also achieve a striking composition by striving for a contrast in texture, growth habit, and plant height. The leaves of cannas contrast nicely with purple fountain grass. If you are growing your purple fountain grass in a pot, move the container in front of oakleaf hydrangea in the fall. The purplish fall foliage and contrasting texture of the latter will provide an effective backdrop. And for the foreground, install a short plant with a growth habit that contrasts with the upright purple fountain grass, for example, annual lobelia or blue fescue.

Varieties of Purple Fountain Grass

Another cultivar of the species is Pennisetum setaceum or "Fireworks." The leaves are variegated with burgundy in the middle and hot pink at the edges. It grows three to six feet in height, with a spread of one to three feet. It is a perennial in zones 9 to 10. But P. setaceum is not the sole species in this genus. Fortunately for Northerners, P. alopecuroides can be grown as a perennial in zones 5 to 9. Types of P. alopecuroides include the following:

  • Burgundy Bunny: Stands at 16 inches tall with a spread of 16 inches. Foliage has hints of red in summer, but color intensifies to a deep reddish-purple in fall. Flower heads are buff-colored.
  • Little Bunny: Stands at 12 inches tall with a slightly greater spread. Lacks the colorful foliage of Burgundy Bunny. Also features buff-colored flowers.