Grass · Sonoran native
Mexican Feather Grass
Nassella tenuissima · Poaceae
Also called: Finestem Needlegrass, Fineleaved Nassella, Argentine Needlegrass, Pony Tails, Stipa tenuissima (former name)
Mexican Feather Grass (Nassella tenuissima) is a very low-water grass native to the Sonoran Desert region well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate.
Mexican Feather Grass at a glance
- Water use
- Very Low (established)
- Sun
- Full sun; tolerates very hot, dry Tucson exposures including reflected heat
- Mature size
- 1.5-2 ft tall and wide, with fine, hair-like fountaining foliage
- Growth rate
- Fast
- Bloom
- Silvery-green to golden, feathery flowers fading to blond/straw seedheads, Late spring into summer
- Cold hardiness
- Cold hardy to about USDA zone 6-7; fully hardy in Tucson. Stays largely evergreen through mild winters.
- Soil
- Lean, well-draining soil; excellent for gravelly, sandy, rocky, alkaline desert soils. Sharp drainage essential.
- Native range
- Native to the southwestern U.S. (including parts of Arizona, New Mexico, Texas), northern Mexico, and Argentina; ornamental nursery stock is often of non-local origin
- Best used as
- Soft-textured xeriscape accent, Mass planting and meadow-style drifts, Containers, Erosion control on dry slopes
- Wildlife
- Minor cover value; not a notable pollinator plant.
- Toxicity
- Non-toxic to pets and humans, but the fine awned seeds are a nuisance and the foliage is not readily digested by livestock. Seeds can lodge in dog/animal fur and ears.
How to grow Mexican Feather Grass in Tucson & the low desert
Watering
Extremely drought tolerant once established. In Tucson, water deeply only every 1-2 weeks in summer and monthly or less in winter; thrives on neglect. Overwatering causes flopping and crown rot.
Fertilizer & nutrients
Essentially none needed; it prefers lean soil. Skip fertilizer or use at most a very light spring feeding. Rich soil and over-fertilizing reduce its fine, arching habit.
Pruning & care
Comb out or rake spent foliage in late winter, or shear to a few inches in late winter to refresh. Deadhead/shear after flowering to limit self-sowing. Semi-evergreen in Tucson.
Notes
IMPORTANT for Tucson: this grass self-sows aggressively and is a documented ornamental escapee/invasive in parts of the western U.S. (e.g., naturalized in California). Although it occurs natively in the broader Southwest, it is widely discouraged for desert landscaping because of reseeding; shear off seedheads before they ripen, or choose a sterile, non-spreading alternative such as 'Hameln' fountain grass if low maintenance and weed control are priorities. Beautiful fine texture and movement, but plant responsibly.
Sources: University of Arizona Cooperative Extension; Arizona-Sonora Desert Museum; California Invasive Plant Council (Cal-IPC); Wikipedia (range and invasiveness overview)