Grass
Purple Fountain Grass
Cenchrus setaceus 'Rubrum' · Poaceae
Also called: Red Fountain Grass, Purple Fountaingrass, Pennisetum setaceum 'Rubrum' (former name)
Purple Fountain Grass (Cenchrus setaceus 'Rubrum') is a low-water grass well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate.
Purple Fountain Grass at a glance
- Water use
- Low (established)
- Sun
- Full sun; needs all-day sun for best burgundy color and dense, upright form. Tolerates intense reflected desert heat.
- Mature size
- 3-4 ft tall and 2-3 ft wide, with plumes arching above the clump.
- Growth rate
- Fast
- Bloom
- Coppery-pink to purplish foxtail plumes above burgundy-red foliage, Late spring through fall (Apr-Oct).
- Cold hardiness
- USDA 9a-11; frost-tender. Tucson winter frosts often kill the top growth or the whole plant; treated as a tender perennial or annual replant. Mulch the crown for cold protection.
- Soil
- Very adaptable; thrives in poor, well-drained, alkaline desert soils. Needs good drainage.
- Native range
- North Africa, the Middle East, and southwestern Asia
- Best used as
- Accent and color grass in beds, Mass plantings and borders, Container specimen, Median and commercial landscape filler
- Wildlife
- Plumes provide some seed and cover; limited native wildlife value.
- Toxicity
- Not considered toxic to people or pets; foliage edges can be sharp.
How to grow Purple Fountain Grass in Tucson & the low desert
Watering
Drought tolerant once established. Water deeply every 7-14 days in summer for lush growth, every 3-4 weeks in winter. Tolerates infrequent irrigation but looks fuller with regular water.
Fertilizer & nutrients
Low needs; one application of balanced or slow-release fertilizer in spring is sufficient. Over-fertilizing causes floppy growth.
Pruning & care
Cut the entire clump back to about 4-6 in in late winter/early spring before new growth to remove frost-damaged and tired foliage and keep it neat.
Notes
Showy burgundy color but use with caution: the green species fountaingrass (Cenchrus setaceus) is an Arizona-listed noxious weed and aggressive invader of desert washes and canyons. 'Rubrum' is NOT banned and is marketed as sterile, but its sterility is overstated and it can still set some viable seed - many Arizona horticulturists discourage planting it and recommend native bunchgrasses (deergrass, Muhlenbergia) as alternatives. Self-sows less than the green form but monitor and remove seedlings.
Sources: Arizona Department of Agriculture noxious weed list (green fountaingrass); Arizona-Sonora Desert Museum / NPS Saguaro NP fountain grass guidance; Southwest Gardener (purple fountain grass sterility discussion); University of Arizona Cooperative Extension