Ornamental · Poaceae
Mexican Feather Grass
Nassella tenuissima
Drop it into lean soil and full sun and watch this grass dance all season long, just stay ahead of its seed.
Full sun
Every 10–21 days
90–120 days
USDA 7–10
Overview
Mexican feather grass puts on a show that never sits still. Its hair-thin blades grab the faintest breeze and surge into rippling waves, then warm from green to a glowing wheat tone as the season rolls on. It builds a crisp, fountain-shaped clump that lights up a gravel garden and weaves a thread of motion straight through a border.
Here is a tough, drought-hardy perennial that came up swinging from the dry country of the southwest and Mexico. Get it rooted and it powers on through heat and lean ground that flatten fussier plants, asking almost nothing in return. It even knows when to coast, taking a brief summer breather and browning off before it bounces back green the moment cooler air arrives.
There is one thing that keeps a grower on their toes: the seed. A single clump launches thousands of wind-borne seeds, and across mild-winter regions like California it has leapt the garden and gone invasive in open grassland. Stay one step ahead, clipping the seed heads before they ripen, and it rewards you as a graceful, near-effortless plant. Drop your guard and it charges off into ground it was never meant to reach.
Care
The short version: hand it full sun and the sharp drainage of lean, sandy soil, water it sparingly once it digs in, leave the fertilizer alone, comb it out each late winter, and snip the seed heads before they ripen to keep it on a leash.
Light
Pour on the full sun and it answers with the richest color and the tightest, most upright clump going. It will take a touch of afternoon shade, but lay on too much and it sprawls open and drops that snappy fountain shape.
Water
Once it digs in, this grass is very drought tolerant and runs happily on a drink every 10 to 21 days, even less when the air cools. Hit it with a deep soak now and then through a long dry spell, but never let it sit in soggy ground, which rots the roots fast.
Soil
Plant it into lean, sharply drained sandy loam and it takes off, and it shrugs off rocky or clay ground too as long as that ground stays dry. It rolls with a wide pH band from 5.5 to 8.0, so acidity rarely trips it up; wetness is the thing to watch every time.
Temperature
It powers through a huge range, from about 0°F to 100°F (-18°C to 38°C), which spans USDA zones 7 through 10. A hard winter below that range knocks it out, so colder gardens get the most out of it by running it as a short-lived seasonal plant.
Humidity
Dry air is right in its wheelhouse, since this is a plant of arid country. High humidity does it no favors and can even set it back by keeping the crown damp, so hand it open space and moving air over a stuffy, sheltered corner.
Feeding
Skip the fertilizer and barely look back. It rips along in poor soil, and a light spring feed is the absolute ceiling of what it wants, if even that, since rich ground just flops it over and cranks out still more seed.
Pruning
Comb or cut the strawy old blades back in late winter or early spring before the new flush takes off, and shrug at the scruffy look it wears through its summer rest. The move that matters most is shearing the seed heads before they ripen to stop the plant from making a break for it.
Repotting
In a pot it barely ever needs a move, but lift and divide it the moment roots circle the pot, the center dies out, or it dries out fast after every watering. Replant the healthy outer pieces into fresh, gritty mix and toss the spent middle.
Size & spacing
A grown clump shoots up to about 12 to 24 inches (30 to 61 cm) tall and just as wide. Space plants the same 12 to 24 inches (30 to 61 cm) apart so every fountain gets room to arch out and put on its full display without crowding the next.
When to plant
Get the season rolling with no fuss at all. Fire seed up indoors in late winter, six to eight weeks before your last frost, then send young plants out once the cold clears, from spring into early summer. The feathery heads break out from June through September, the most eye-catching stretch of all, so clip them before they ripen to hold the spread in check.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring, 6-8 weeks before last frost
- Plant: After last frost, spring through early summer
- Harvest: June to September
Hardiness
USDA hardiness zones: 7–10
Temperature: down to -18°C
Troubleshooting
Almost every hiccup with this grass tracks back to one of two things: seeding that surges out of bounds, or roots left sitting too wet. That alarming midsummer browning? It is just the plant catching its breath. Match what you spot below and you will know in a heartbeat whether to jump in or let it ride.
Seedlings springing up everywhere, even past the garden edge
This is self-seeding, the plant's one big drawback. A single clump launches thousands of wind-borne seeds that stockpile a long-lived seed bank and sail off into lawns, paths, and wild ground. Get ahead of it: cut and bag the feathery seed heads before they ripen, yank young volunteers roots and all, and bin spent plants instead of composting them anywhere the grass runs wild.
Fix:
- Cut off and bag the feathery seed heads before they ripen and shed seed
- Pull or dig volunteer seedlings while young, including the roots
- Remove and dispose of spent plants in the trash, not compost, where invasive
The center of the clump going brown and mushy
Soggy soil triggers root rot, and this grass flat-out refuses wet feet. The crown and roots go soft and dark wherever drainage stalls or watering piles on. Pull back the water and sharpen the drainage, then lift the clump, rescue the healthy outer growth, and toss the dead center. Keep in mind an old plant may also just be running out its short life.
Fix:
- Improve drainage and reduce watering
- Lift and divide healthy outer portions, discarding the dead center
- Replant in sharply drained, lean soil
Strawy, brown foliage that looks dead by midsummer
Most of the time this is plain summer semi-dormancy, the plant's natural heat response and no reason to panic. The crown stays alive underneath, and fresh green growth charges back once the weather cools or you cut it down. Old dead blades piling up just drag the look down, so comb them out by hand or rake and shear the clump in late winter.
Fix:
- Comb out dead blades by hand or rake
- Cut foliage back in late winter to early spring to refresh growth
Sticky blades, twisted growth, or small leaf spots
Sticky, distorted foliage flags aphids feeding on the blades, while spotting points to leaf spot disease. Knock the aphids off with a strong jet of water and they rarely storm back in any number. Strip the worst-spotted leaves and throw the clump open so air rushes through it.
Fix:
- Rinse aphids off with a strong jet of water
- Remove badly spotted foliage and improve air circulation
Toxicity
Great news for anyone growing it around animals: Mexican feather grass is not toxic to cats, dogs, horses, or anything else, and it poses no danger to people either. The only things to watch are the bristly seeds, which can snag in fur or lodge in a dog's paw like a foxtail, and the pollen, which can stir up hay fever in those prone to it.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
No toxins lurk here, so a curious cat faces zero danger. A cat that chews the blades might bring them back up, and the fine seeds can snag in a long coat.
Dogs Safe
Dogs run safe around it and can nibble away. Just watch the bristly awns, which tangle in fur and bore into paws or ears like a foxtail, so brush them out after a romp through the clump.
Horses Safe
Horses come to no harm at all, since it is not poisonous and grazes down without trouble.
Rabbits Safe
A rabbit can nibble the foliage all day with zero risk of poisoning.
Livestock Safe
Cattle, goats, and sheep can graze it freely without harm, though it brings them little real feed value.
Birds Safe
It is harmless to birds, which love to work the ripe seed and end up hauling it well beyond the garden.
People Safe
No part of the plant poisons people, so handle it freely. The grass pollen can fire up symptoms in anyone prone to hay fever, which is the one thing to flag.
The fine, bristly seeds and awns can cling to and tangle pets' coats (a minor foxtail-type mechanical nuisance), and pets that nibble grass may vomit. Grass pollen may bother allergy-prone people.
Varieties
The lineup is short and sweet, so picking one is a breeze. A couple of names crop up at the nursery, and one group of look-alikes earns a real spot on the list if you crave the same effect without the runaway spread.
Pony Tails
Pony Tails leads the pack as the most widely sold selection, snapped up for its unusually soft, fine foliage that streams in the lightest breeze, though it self-seeds and bolts just as freely as the species.
Stipa tenuissima (synonym)
Stipa tenuissima is the very same plant wearing its older botanical name, still in heavy nursery use, so you will keep spotting it labeled Stipa rather than Nassella.
Native needlegrasses (Nassella / Stipa species)
Native needlegrasses like purple needlegrass deliver the same airy texture without the invasive streak, making them the smart grab wherever the Mexican species causes trouble.
How to propagate
Cranking out more of this grass is a snap, with two routes ready to go. The pick comes down to one question: how much you mind it seeding around.
SeedEasy
Sow indoors late winter to early spring, or it self-sows readily outdoors · One growing season
Seed is the fast lane, and the plant practically sows itself, popping up all over the moment it sets seed. Kick it off indoors in late winter to early spring, or just let it self-sow outdoors, and a seedling rounds into a full clump within one growing season. That same drive is exactly why it bolts where you do not want it, so rein the seeding in wherever it turns into a problem.
DivisionEasy
Spring · One growing season
Division is the clean play for making more without flinging seed around. Lift an established clump in spring, tear it apart, ditch any dead center, then replant the living outer pieces and they dig in over a single season.
Myths
Mexican feather grass is a harmless, well-behaved ornamental wherever it grows.
Not so fast. It self-seeds hard and carries an invasive listing in California and other mild-winter regions, where it vaults the garden fence and overruns native grass across open country. Some areas now discourage or outright ban planting it. Clip the seed heads before they ripen, and where it runs wild, grab a native bunchgrass instead.