Pennisetum setaceum (Fountain Grass): Complete Growing Guide
Complete guide to growing Pennisetum setaceum (fountain grass) — a graceful ornamental grass with feathery plumes. Covers care, invasiveness concerns, non-invasive alternatives, and companion plants.
About Fountain Grass — And an Important Caveat
Few ornamental grasses match the elegant movement and texture of Pennisetum setaceum. Its arching mounds of fine, narrow foliage topped with feathery pink-purple plumes from summer through frost create exactly the kind of soft, naturalistic effect that modern garden design prizes. Native to North and East Africa, the Middle East, and parts of the Arabian Peninsula, this fast-growing grass reaches 3–5 feet (90–150 cm) tall and forms graceful, fountain-like clumps that sway in the lightest breeze.
However, there’s a critical issue to address before planting: Pennisetum setaceum is classified as invasive in several US states, including California, Hawaii, Arizona, Florida, and Nevada [1][2]. The green species form (as distinct from the purple-leaved cultivar ‘Rubrum’, which is sterile) produces viable seed that can spread into wildlands, outcompete native plants, and increase fire risk. In regions where it’s listed as invasive, do not plant the green species form. Check your state’s invasive species list before buying.
The good news: the widely available cultivar ‘Rubrum’ (Purple Fountain Grass) is sterile and does not produce viable seed, making it a non-invasive alternative suitable for most gardens. In cooler climates (zones 4–8), the green species is not hardy enough to overwinter and is grown as an annual — eliminating the self-seeding concern, since it dies in winter before setting seed. The invasiveness issue is primarily a concern in frost-free zones 9–11 where the plant can persist year-round and seed freely.
With that understanding in place, here’s how to grow it responsibly.
Seasonal Garden Calendar
Know exactly what to plant, prune and sow — every month of the year.
Quick Reference
| Feature | Details |
|---|---|
| Scientific Name | Pennisetum setaceum (syn. Cenchrus setaceus) |
| Common Names | Fountain Grass, African Fountain Grass, Tender Fountain Grass |
| Family | Poaceae (grass family) |
| Plant Type | Warm-season ornamental grass (perennial in zones 9–11; annual elsewhere) |
| Mature Size | 3–5 ft tall (90–150 cm); 2–4 ft wide (60–120 cm) |
| Growth Rate | Fast |
| Hardiness Zones | USDA 9–11 (perennial); grown as annual in zones 4–8 |
| Bloom Time | Midsummer to frost |
| Flower Colour | Pink-purple plumes (species); burgundy-red (‘Rubrum’) |
| Light | Full sun (6+ hours) |
| Soil | Any well-drained soil; tolerates sand, loam, clay |
| Water | Low to moderate; drought-tolerant once established |
| Toxicity | Non-toxic to humans and pets |
| Native Range | North and East Africa, Middle East, Arabian Peninsula |
| Special Features | Drought-tolerant, deer resistant, movement and texture, excellent container plant, architectural accent |
| Invasiveness | Green species: invasive in CA, HI, AZ, FL, NV. ‘Rubrum’: sterile, non-invasive |
Key Cultivars
Choosing the right cultivar matters — both for garden performance and environmental responsibility.
‘Rubrum’ (Purple Fountain Grass)
The most widely sold cultivar. Deep burgundy-red foliage with darker plumes. Reaches 3–4 feet (90–120 cm). Sterile — does not produce viable seed. This is the safest choice for any region, as it cannot escape into wildlands. Hardy only in zones 9–11 as a perennial; grown as an annual everywhere else. It’s the cultivar to buy if you’re in any doubt about invasiveness.
‘Rubrum Dwarf’ (Dwarf Purple Fountain Grass)
Compact form reaching 2.5–3 feet (75–90 cm). Same burgundy-red foliage and sterile habit as ‘Rubrum’ but in a smaller package. Ideal for containers and the front of the border.
Species Form (Green Fountain Grass)
Light green foliage with pink-purple plumes that can appear almost white in bright light. Reaches 4–6 feet (120–180 cm) — the largest form. Produces viable seed and is the form classified as invasive. Only appropriate in zones 4–8 where it’s grown as a frost-killed annual, or in managed garden settings far from natural areas in warmer zones.
Care Guide
Light
Full sun is non-negotiable. Pennisetum setaceum needs six or more hours of direct sunlight daily for compact growth, abundant plumes, and the best foliage colour (particularly in purple cultivars). UF IFAS notes that plants “grow poorly in partial shade and droop over” [3]. Even light shade produces floppy, sparse plants — this is one grass that truly needs maximum light.
Soil
Fountain grass is remarkably adaptable. It grows in sand, loam, or clay, and tolerates acidic to slightly alkaline soils. The only requirement is decent drainage — while it handles dry soil beautifully, persistently waterlogged ground causes root rot.
In practice, the less you improve the soil, the better the results. Lean, well-drained soil produces compact, upright plants with the best plume production. Rich, fertile soil encourages lush but floppy growth that needs cutting back to stay tidy. This is a grass from semi-arid African grasslands — it doesn’t want pampering.
Temperature and Hardiness
Understanding fountain grass’s temperature limits is essential for choosing the right approach. As a warm-season grass from Africa, it thrives in heat and humidity — the hotter and sunnier the summer, the better it performs. It’s fully perennial in zones 9–11, where winter temperatures stay above 20°F (−7°C).
In zones 7–8, it may survive mild winters with heavy mulching, but performance is unreliable — most gardeners in these zones treat it as an annual to avoid disappointment. In zones 4–6, it’s definitively annual: the first hard frost kills the top growth, and the roots don’t survive winter. This frost sensitivity is actually a safety feature from an environmental perspective — in cold climates, there’s zero risk of the plant establishing permanently and becoming invasive.
If you’re growing ‘Rubrum’ as an annual in zones 6–8, one trick that extends the season is to wait until soil temperatures are genuinely warm (above 18°C / 65°F) before planting. Fountain grass sulks in cool spring soil — plants put in a month later than you’d think often catch up and surpass earlier plantings by midsummer.
Plant too early and frost kills it, too late and heat stunts it — pennisetum alopecuroides fountain grass has the window.
Planting
In zones 9–11 (perennial), plant in spring through early autumn. In zones 4–8 (annual use), plant after all frost risk has passed — typically late May or early June.
Space plants 36–60 inches (90–150 cm) apart to allow room for the mature clump to develop its full fountain shape. This spacing looks sparse at first but fills in rapidly. Set the crown at soil level, water thoroughly, and mulch lightly around (not over) the base.
Container planting: use a pot at least 14 inches (35 cm) in diameter with drainage holes, filled with a well-draining potting mix. ‘Rubrum’ and ‘Rubrum Dwarf’ are especially popular as container accent plants on patios and flanking entrances.
Watering
Water regularly during the first 4–6 weeks to establish the root system. Once established, fountain grass is genuinely drought-tolerant — its deep, well-developed root system pulls moisture from well below the surface. In most climates, established plants need supplemental water only during prolonged dry spells.
We cover the exact watering frequency and method in catalog barnyard grass.
Container plants dry out faster than in-ground plantings and need checking every few days in summer. Water when the top 2 inches (5 cm) of soil feel dry to the touch.
Fertilising
Little to none. Like most ornamental grasses, fountain grass needs minimal supplemental nutrition. A light mulch of compost around the base in spring is sufficient for in-ground plants. Container plants benefit from monthly liquid feeds during the growing season. Avoid high-nitrogen fertilisers — they promote rank, floppy growth.
Cutting Back
In zones 9–11 (perennial): Cut the entire plant back to 4–6 inches (10–15 cm) above ground level in late winter or early spring, before new growth emerges. This removes the previous year’s dead foliage and allows fresh, clean growth to develop. Use sharp hedge shears or a power trimmer — wear gloves, as the leaf blades can cut skin.
In zones 4–8 (annual): The plant dies with the first hard frost. Remove dead foliage and root mass before winter or in early spring. Since the plant won’t return, there’s no regeneration to worry about.
Winter Care (Zones 9–11)
In zones 9–10, the foliage goes semi-dormant and may brown at the tips during winter. Leave it in place until late winter, then cut back hard for a fresh start. In zone 11 (truly frost-free), the plant may stay semi-evergreen year-round and simply needs an annual hard prune to keep it tidy.
If growing ‘Rubrum’ as an annual in colder zones and you want to save the plant over winter, dig up the clump before the first frost, pot it, and bring it indoors to a bright, cool location (an unheated conservatory or greenhouse is perfect). Water sparingly through winter. Move back outdoors after the last spring frost. This is worth doing for large, well-established specimens but not practical for mass plantings.
Propagation
Division (Recommended)
Divide established clumps in spring as new growth appears. Dig the entire clump and split into sections using a sharp spade — each division should have a good root portion and several growing points. Replant immediately, water well, and they’ll establish quickly. Division is the only method for sterile cultivars like ‘Rubrum’.
Seed (Species Form Only)
The green species form can be grown from seed. Sow indoors 6–8 weeks before the last frost, pressing seeds onto the surface of moist compost (they need light to germinate). Keep warm (20–25°C / 68–77°F) and moist. Germination takes 14–21 days. Transplant outdoors after hardening off and all frost risk has passed. Do not collect or sow seed in regions where P. setaceum is listed as invasive.
Common Problems and Solutions
Floppy, Open Habit
Almost always caused by insufficient sun, overly rich soil, or excess nitrogen. In full sun with lean soil, fountain grass maintains its signature upright, arching form without support. If an established plant flops, reassess the light and fertility levels before reaching for stakes.
Poor Plume Production
Insufficient sun is the usual cause. Young plants (first year from division or planting) may also produce fewer plumes while establishing their root system. Container plants may underperform if they’ve become rootbound — repot into a larger container or divide.
Brown Leaf Tips in Summer
Occasional browning of lower or older leaves is normal — the plant naturally cycles out older foliage. Widespread browning during active growth usually indicates drought stress. Water deeply and the plant recovers quickly. In humid climates, rust or leaf spot may cause browning — improve air circulation and avoid overhead watering.
Pests and Diseases
Remarkably pest-free. Thrips may occasionally cause minor leaf damage, and mealybugs can appear on container plants brought indoors for winter. Neither is usually serious enough to warrant treatment beyond insecticidal soap. No significant disease problems are reported [3].
Self-Seeding (Species Form)
In zones 9–11, the green species form can self-seed prolifically. Remove plumes before seeds mature if you want to prevent spread, or — better — plant the sterile ‘Rubrum’ cultivar instead. Never allow seed to spread into natural or semi-natural habitats.
Garden Design and Companion Plants
Design Uses
Fountain grass is one of the best plants for adding movement and soft texture to the garden. The arching foliage sways in the slightest breeze, and the feathery plumes catch backlight beautifully — plant with the afternoon sun behind the plumes for maximum dramatic effect. This backlighting trick transforms the plant from attractive to genuinely spectacular. I use this technique in my own garden with a west-facing gravel bed, and the effect in late afternoon is worth the entire cost of the planting.
Use as a specimen in a large container, a focal point in a gravel garden, a massed planting along a driveway, or a mid-border accent in mixed perennial plantings. The purple cultivar ‘Rubrum’ is especially effective as a contrast plant among silver-foliaged plants like Artemisia or Senecio, or alongside golden-flowered companions for a warm autumn palette.
Companion Plants
- Echinacea ‘Sundown’ — sunset-orange coneflowers against purple grass foliage is a striking warm-toned combination. Both are drought-tolerant and share the same sun requirements.
- Rudbeckia hirta ‘Prairie Sun’ — golden-yellow daisies provide a bright complement. The contrasting textures (solid daisies vs. feathery plumes) add interest.
- Salvia ‘Hot Lips’ — red-and-white flowers echo the warm palette and attract hummingbirds.
- Sedum (Hylotelephium) — flat flower heads in pink or russet complement the grass’s vertical plumes and provide late-season colour continuity.
- Agastache ‘Blue Boa’ — cool violet-blue spikes against warm purple grass creates a sophisticated colour contrast.
Non-Invasive Alternatives
If you love the fountain grass look but live where P. setaceum is restricted, consider these alternatives:
- Pennisetum alopecuroides (Hardy Fountain Grass) — similar arching habit and plumes but fully hardy (zones 5–9) and not classified as invasive. Cultivars like ‘Hameln’ (compact) and ‘Moudry’ (dark plumes) offer variety.
- Nassella tenuissima (Mexican Feather Grass) — even finer texture, but note that this species is also invasive in some regions. Check local lists.
- Miscanthus sinensis ‘Gracillimus’ — larger scale but similar graceful movement and late-season plumes.
Frequently Asked Questions
Is Pennisetum setaceum invasive?
The green species form is classified as invasive in California, Hawaii, Arizona, Florida, Nevada, and other warm regions where it can persist year-round and self-seed. The purple cultivar ‘Rubrum’ is sterile and not considered invasive. In cold climates (zones 4–8), the species is annual and cannot establish permanently.
Is purple fountain grass (‘Rubrum’) perennial?
Only in zones 9–11. In colder zones, it’s killed by the first hard frost and must be replaced each year or brought indoors for winter. Many gardeners in zones 6–8 treat it as a premium annual — buying fresh plants each spring for their containers and borders.
When should I cut back fountain grass?
In zones 9–11 (perennial), cut back to 4–6 inches above ground in late winter before new growth starts. In cold zones (annual use), remove the frost-killed plant any time after the first hard freeze, or leave it for winter texture and remove in early spring.
Does fountain grass attract wildlife?
The plumes attract seed-eating birds in autumn, and the dense foliage provides cover for small wildlife. It’s not a significant pollinator plant (grasses are wind-pollinated), but the overall habitat value in a mixed planting is positive. Deer and rabbits leave it alone.
How fast does fountain grass grow?
Very fast. From a spring planting, ‘Rubrum’ typically reaches its full size of 3–4 feet by midsummer. The green species form grows even faster, potentially reaching 4–6 feet in a single season. This rapid growth is one reason fountain grass works so well as an annual — it delivers a full-sized, mature display in the same season it’s planted, unlike most perennials which take two or three years to hit their stride.
Can I grow fountain grass indoors?
Not really — it needs full sun and air movement that indoor conditions simply can’t provide. However, it can be overwintered indoors in a bright, cool room as a dormant or semi-dormant plant, then moved back outside in spring. This is maintenance, not indoor growing — the plant won’t look its best during the winter months.
Can I grow fountain grass in a pot?
Yes — it’s one of the best ornamental grasses for containers. Use a pot at least 14 inches in diameter with good drainage. ‘Rubrum’ and ‘Rubrum Dwarf’ are particularly popular container choices. Water when the top 2 inches of compost feel dry and feed monthly with liquid fertiliser during summer.
References
- California Invasive Plant Council. “Pennisetum setaceum Profile.”
- UC Riverside Center for Invasive Species Research. “African Fountain Grass.”
- University of Florida IFAS Extension. “Pennisetum setaceum Tender Fountain Grass.” FPS463. [3]
- University of Wisconsin-Madison Extension. “Fountain Grass, Pennisetum alopecuroides.” Wisconsin Horticulture.
References
- California Invasive Plant Council. “Pennisetum setaceum Profile.”
- UC Riverside Center for Invasive Species Research. “African Fountain Grass.”
- University of Florida IFAS Extension. “Pennisetum setaceum Tender Fountain Grass.” FPS463.
- University of Wisconsin-Madison Extension. “Fountain Grass, Pennisetum alopecuroides.” Wisconsin Horticulture.
