Ornamental · Poaceae
Feather Reed Grass
Calamagrostis × acutiflora
In full sun, feather reed grass holds narrow stems and tan feathered plumes bolt upright from June straight through winter.
Full sun
Every 5–10 days
USDA 4–9
3–5 ft · 0.9–1.5 m
Overview
Feather reed grass forms a tight clump of slim green blades that sends up tall, narrow flower stalks topped with feathery plumes. It is a sterile hybrid of two European grasses, and the best-known form, Karl Foerster, was named Perennial Plant of the Year in 2001. Fresh green leaves push up in spring, and by early summer the stems carry soft, narrow plumes that catch the light.
The standout trait is the strict vertical habit: every stem runs dead straight up and keeps that line even after the plumes dry to a wheat-tan color. The narrow blades and rigid stalks hold their shape long after looser grasses sag. It is a cool-season grass, putting on most of its blade growth in the cooler stretches of spring and fall and easing off through the hottest weeks.
Once rooted, the clump asks for almost nothing. Hardy from zone 4 to zone 9, it takes heavy clay, deep cold, and soggy ground that would rot other grasses. Let the dried plumes and stiff stems stand all winter for upright structure, then shear the whole clump low before the new green shoots break in spring.
Care
The short version: full sun, average to moist soil, and little fuss. Water it through a long dry spell, hold back on feeding so the narrow stems stay bolt upright, and cut the whole clump to the ground once a year in late winter.
Light
Plant it in full sun for the stiffest, straightest stems and the most plumes. It tolerates partial sun or light shade, but the dimmer the spot, the more the narrow stalks lean and flop and the fewer feathered heads they raise.
Water
Settled in, it copes with a wide range, from dry banks to wet, heavy ground that drowns most grasses. It grows best in fertile soil that never dries to dust, so soak the clump through any long drought. Water every 5 to 10 days in a dry stretch, and otherwise let rainfall carry it.
Soil
Nearly any soil will do. Well-drained fertile loam suits it best, yet it handles heavy clay, thin poor ground, and damp sites far better than other ornamental grasses, which is much of why it gets planted so often.
Temperature
This is a hardy, cold-proof grass, at ease from roughly -29°F to 100°F (-34°C to 38°C). The hard freezes of a zone 4 winter do not touch it, though the blades may sulk and brown a little through a hot, sticky summer.
Humidity
Outdoor humidity makes no difference, so there is no target reading. What counts is air movement: still, muggy air inside a packed planting is exactly what lets rust settle into the blades.
Feeding
Feed lightly in spring with a balanced fertilizer or a thin layer of compost, and leave it at that. Overfed, rich ground forces soft, weak growth that flops and wrecks the upright shape you wanted.
Pruning
Just one cut all year. Shear the entire clump to a few inches above the ground in late winter or very early spring, before the new green shoots emerge, and the blades regrow within weeks.
Repotting
In the ground the job is dividing, not repotting. Every few years, once the center thins or the clump weakens, dig and split it in spring or fall, keep the firm outer pieces, and discard the dead middle.
Size & spacing
In flower a clump stands 3 to 5 feet (91 to 152 cm) tall while staying tightly narrow, spreading only about 18 to 30 inches (46 to 76 cm). That slim footprint is what makes it such a clean vertical accent or row.
When to plant
Set feather reed grass out in spring or fall, when the soil is cool and roots can take hold without summer strain. The feathery flower plumes rise in early summer, around June, then stiffen into tan spikes that stand through fall and on into winter.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring or fall
- Harvest: Early summer (June); plumes persist through fall and winter
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Nearly every problem with feather reed grass traces back to too much shade, too much summer heat, or a clump grown old in the middle. The blades and stems tell you which one it is. Find the matching look below, then make the single change that corrects it.
Rust-orange flecks dusting the surface of the blades
Those raised orange-to-brown specks on the leaf surface are rust disease, and a finger drawn across them comes away powdery. They flare after stretches of rain or hot, wet air. Pull the worst-marked blades, thin the clump so air slips between the stems, and keep the foliage dry. Cut away any spotted growth at the late-winter trim so the fungus does not overwinter.
Fix:
- Improve air circulation and avoid overhead watering
- Remove and discard badly affected foliage
- Cut back and dispose of infected growth at the late-winter cleanup
A hollow, bare ring opening at the heart of the clump
An aging clump dies away in the middle while a live ring of blades keeps spreading at the rim, leaving a doughnut shape. That hollow center is the plant signaling for division. Lift it in spring or fall, separate the strong outer growth to replant, and bin the dead heart. Repeat the split every few years to keep the blades packed solid.
Fix:
- Dig and divide the clump in spring or fall
- Replant healthy outer divisions and discard the dead center
Green blades fading to dull brown in mid-summer heat
The narrow leaves turn flat and tan when the air goes hot and sticky, because this is a cool-season grass that pushes its real growth in spring and fall. The browning is just a summer pause, sharpest in southern gardens. Keep water at the roots through the worst weeks and the blades flush back to green as the air cools.
Fix:
- Water during prolonged heat and drought
- Tolerate the temporary summer decline; do not cut the whole plant back
- Site in full sun in cooler regions for best vigor
Tall stems bowing outward instead of standing as a tight column
When the poker-straight stalks start to splay and arc toward the ground, the cause is nearly always too much shade or too rich a soil. Shift the clump into full sun and back off the feeding. Lean ground and bright light are what hold each narrow stem dead vertical.
Fix:
- Transplant to a full-sun location
- Reduce fertilization and avoid overly rich soil
Toxicity
This grass is easy company. Feather reed grass is non-toxic and absent from the ASPCA poison lists, so it poses no chemical danger to cats, dogs, or anyone in the house. The catch is purely physical: the blade edges and seed heads are sharp enough to scratch, and a pet that gulps a wad of grass may bring it back up.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
Safe around cats. One that bites off a narrow green blade may bring it back up like any grass, but the leaf holds nothing poisonous.
Dogs Safe
No toxins in the blades, so a dog can sniff and chew freely. A big mouthful of the coarse leaves might come back up, and that is the whole of it.
Horses Safe
Not a listed danger for horses. The only thing to watch is the stiff, sharp-edged blades, which can scratch a muzzle brushing past.
Rabbits Safe
Nothing poisonous for rabbits. The leaves are coarse with cutting edges, so they make a poor snack and usually get passed over.
Livestock Safe
Cattle, goats, and sheep can graze beside it with no poisoning. It is raised for its tall plumes, not as feed, so stock seldom touch the wiry blades.
Birds Safe
No harm to birds, which may peck at the feathery seed heads. The favored forms are sterile, though, so the plumes carry next to no seed.
People Safe
Safe to handle. Pull on gloves at cutback time all the same, since the leaf edges and the spiky seed heads can nick bare skin.
Foliage and seed heads have sharp edges and points that can scratch; grass pollen may bother allergy sufferers, and pets that nibble grass may vomit, but it is not poisonous.
Varieties
A handful of named forms account for almost every feather reed grass on the garden-center bench. These are the ones worth telling apart by blade and plume.
Karl Foerster
The original strict-upright sterile hybrid, Perennial Plant of the Year in 2001, with slim green blades and feathered plumes that mature tan and shed no seed.
Overdam
A shorter variegated form near 3 feet tall, its green blades crisply rimmed along each edge with a thin white stripe.
Avalanche
A variegated pick reaching close to 4 feet, each blade split by a wide white band running straight down the middle.
Calamagrostis brachytricha (Korean feather reed grass)
A warm-season relative that forms a looser, arching mound and unfurls soft pinkish plumes in late summer and fall.
How to propagate
Since the popular forms are sterile and set no usable seed, you make more feather reed grass by splitting a clump. It is the same easy cut that keeps an old, hollowing plant young.
DivisionEasy
Spring or fall · One growing season
Splitting the clump is how you make more feather reed grass, and the same cut renews an old plant gone hollow at the core. Lift an established clump in spring or fall, pull apart the firm outer growth, and replant those pieces, which root and fill out over a single growing season.
SeedDemanding
Not applicable for sterile cultivars · Not applicable; sterile cultivars set little or no viable seed
Seed gets you nowhere with the usual garden forms. The sterile hybrids such as Karl Foerster produce little or no viable seed in their plumes, so there is nothing worth sowing, and raising the named forms from seed simply does not work.
Myths
All ornamental grasses self-seed and take over the garden.
The garden forms of feather reed grass, with Karl Foerster at the front, are sterile and set little or no living seed. The plumes look full and feathery but carry nothing that will sprout, so the standard cultivars stay put and do not spread. Only the wild species or a rare chance seedling can travel; the named hybrids on the shelf will not.