How to Grow Pennisetum (Fountain Grasses)

Pennisetum ornamental grass with thin green blades with soft, fluffy heads in flower garden

The Spruce / Evgeniya Vlasova

The Pennisetum genus includes a variety of ornamental grasses known for their soft, fuzzy flower plumes. Part of the Poaceae family, these plants are also commonly referred to as fountain grasses. The individual species include both annual and perennial varieties, ranging in size from large to small. The smaller varieties can be kept in containers for a beautiful addition to a patio or entranceway. The foliage of many of these eye-catching grasses is available in an array of beautiful burgundy, purple, and variegated colors. Their lovely flowers are perfect for cut and dried flower arrangements. Some of the well-known species of Pennisetum include feathertop grass (Pennisetum villosum) and pearl millet (Pennisetum glaucum).

Botanical Name Pennisetum
Common Name Fountain grass
Plant Type Ornamental grass
Mature Size One to six feet tall, one to five feet wide
Sun Exposure Full sun
Soil Type Loamy, sandy, clay, moist but well-drained
Soil pH Acidic, neutral
Bloom Time Summer, fall
Flower Color Pink, purple, white, tan
Hardiness Zones 6-9, USDA
Native Area Asia, Africa, Australia

Pennisetum Care

Once established, Pennisetum grasses do not require much maintenance. They are great choices for hot, sunny, humid areas and do well in containers. However, these eye-catching grasses can still be enjoyed outside of their growing zones if you’re willing to grow them as an annual. 

These plants enjoy moist, well-draining soils and are often drought-tolerant once established. They are not often bothered by pests or diseases and are generally rabbit and deer resistant. Besides yearly pruning and occasional watering, these grasses do not demand much attention.  

Warning

Because it is not native to North America, many varieties of Pennisetum are invasive throughout the U.S., particularly in Hawaii and the southern continental region. These plants upset the balance of native flora and fauna and can negatively affect native wildlife. These grasses are also very flammable and can quickly spread fires. 

Pennisetum ornamental grass with thin blades and brown fluffy heads in sunlight

The Spruce / Evgeniya Vlasova

Pennisetum ornamental grass with thin blades and soft fluffy and yellow flower heads closeup

The Spruce / Evgeniya Vlasova

Pennisetum ornamental grass blades with long brownish-purple fluffy flower heads closeup

The Spruce / Evgeniya Vlasova

Light

These plants thrive in full sunshine. They prefer at least six to eight hours of sunlight a day. A bit of shade is acceptable, but too much shade can cause these grasses to take on a leggy, floppy appearance and they might not flower. 

Soil

The Pennisetum genus generally prefers rich, evenly moist soil that is slightly acidic. However, if the soil is well-draining and moist, these grasses can be grown in a mix of clay and sand as well. 

Water

Regular watering will keep any variety of Pennisetum grass happy. The species within this genus prefer moist conditions, so water when the top of the soil begins to feel dry. Aim to keep the soil consistently moist, but never soggy. Some varieties are drought tolerant and will not need as much watering. 

Temperature and Humidity

Pennisetum grasses enjoy warm, humid environments and can be grown as perennials in USDA Hardiness Zones 6 to 9. They thrive in sunny, hot, humid regions. However, these grasses can be grown as annuals in colder zones. They are not reliably hardy or cold tolerant in Zone 5 and lower. 

Fertilizer

Fertilizer is not normally necessary for the healthy growth of the Pennisetum species, but giving these plants some well-balanced fertilizer in the spring won’t hurt. This will help encourage healthy, plentiful growth.

Types of Pennisetum

  • Pennisetum setaceum ‘Rubrum’: Known as purple fountain grass, this variety is famous for its deep purple foliage and soft purple and tan blooms. This is a tender perennial that grows in zones 9-11 but is often used as an annual. They grow to be four feet tall and wide.
  • Pennisetum messiacum ‘Bunny Tails’: This variety was named after its small, pink, fluffy flowers that resemble a bunny’s tail. It is a small variety that only grows to about two or three feet high. 
  • Pennisetum orientale: This variety forms a compact bush of foliage and soft, dusty pink blooms. It reaches a mature height of one to three feet tall. 
  • Pennisetum alopecuroides: This variety is the parent of many other cultivars. It produces two to five feet tall pinkish-purple blooms that mature to a soft brown. 

Pruning

For perennial varieties of Pennisetum, you can cut foliage to the ground in late fall after the grass is done blooming. This will keep the area clean throughout winter and encourage new, healthy growth in the coming growing season. Some gardeners prize the winter interest provided by their ornamental grasses and prefer to cut them down in early spring.

Propagating Pennisetum

Propagating these grasses can easily be done through division in the spring. Here’s how: 

  1. Use a sharp garden shovel to dig around the grass and slice through the root system. 
  2. Slowly work around the separated section until you can gently lift it from the ground. 
  3. Fill in the hole and transfer the new section to its own area. 
  4. Press down on the soil around the transplanted grass and water thoroughly.

How to Grow Pennisetum From Seed

You can also start Pennisetum grasses from seed. To directly sow seeds outdoors, follow these steps: 

  1. In early spring, sow the seeds 18 to 36 inches apart in a sunny area with well-draining, moist soil.  
  2. Lightly cover the seeds with soil and keep them moist. Once temperatures are warm enough for germination, the seedlings should appear in a few weeks. 

To start seeds indoors, follow these steps: 

  1. Start the seeds about two months before the last frost. Sow them in moist, well-draining soil and lightly cover them with soil. 
  2. Keep the soil moist and place the seeds in a sunny, warm spot. 
  3. Once seedlings appear, plant them into the garden after the threat of frost has passed. 

Potting and Repotting Pennisetum

Many varieties of Pennisetum grow well in containers and are perfect for adding texture and interest to patio areas and porches. Soggy soil from trapped water can cause root rot in containers, so it is important to choose a large pot with good drainage holes. Fill the pot with well-draining soil and keep the soil moist, but not soggy. 

Choose a pot that provides several inches of growing room on all sides. When the grass outgrows its container, gently tip the container onto its side and tap the pot to loosen the root system. Slowly work around the pot until the plant can be slid out. Plant the grass into a larger container and fill it in with rich, well-draining soil.  

Overwintering

These grasses cannot survive cold winters in Zones 5 and below and are often grown as annuals in those zones. If you’re located in one of the northernmost hardiness zones, add a layer of mulch before the winter begins to help insulate the roots. If kept in pots, it is best to move the pot indoors before cold temperatures arrive. 

Article Sources
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  1. “Pennisetum Setaceum (Fountain Grass).” Cabi.Org, https://www.cabi.org/isc/datasheet/116202.