Ornamental · Poaceae
Feather Reed Grass
Calamagrostis × acutiflora
Put it in full sun and feather reed grass holds tall and feathery from June straight on through winter.
Full sun
Every 5–10 days
USDA 4–9
3–5 ft · 0.9–1.5 m
Overview
You've probably spotted feather reed grass already, the upright stuff lining driveways or standing tall at the back of a border. It's a sterile hybrid of two European grasses, and its best-known form, Karl Foerster, was crowned Perennial Plant of the Year in 2001. The clump pushes up slim green blades in spring, then sends up tall flower stalks that feather out come early summer.
So what makes it special? That strict vertical habit. The stems rocket straight up and stay in line even after the plumes fade to a wheat color, so it keeps its shape long after looser grasses have flopped over. It's a cool-season grass too, which just means it does its real growing in the milder spring and fall and likes to take it easy when summer gets brutal.
Once it's settled in, it barely asks for anything. Hardy from zone 4 to zone 9, it brushes off heavy clay, harsh winters, and soggy ground that would rot other grasses out. Leave the plumes up over the cold months for some winter structure, then cut the whole clump down before the fresh shoots come up in spring.
Care
The short version: full sun, average to moist soil, and pretty much zero fuss. Water it through a long dry spell, go easy on the food so the stems stay tall, and cut the clump to the ground once a year in late winter.
Light
Give it full sun if you want the straightest, sturdiest stems. It'll put up with partial sun or light shade, but the shadier the spot, the more the stalks lean and flop, and the fewer plumes you'll get out of it.
Water
Once it's established, it can take a lot, anywhere from a dry bank to wet, heavy ground that would drown most grasses. It's happiest in fertile soil that never dries out completely, so be sure to water the clump through a long drought. Give it a drink every 5 to 10 days during a dry stretch, and the rest of the time just let the weather handle it.
Soil
Just about any soil works for it. Well-drained fertile loam is the dream, but it deals with heavy clay, poor dirt, and damp spots way better than other ornamental grasses, which is a big reason gardeners keep coming back to it.
Temperature
This is one tough, cold-hardy grass, happy anywhere from about -29°F to 100°F (-34°C to 38°C). The deep freeze of a zone 4 winter doesn't bother it one bit, though it might pout and brown a little when summer turns hot and muggy.
Humidity
Outdoor humidity isn't something you need to fret over, so there's no target number here. What counts a lot more is air movement, because stagnant, muggy air in a crowded planting is exactly what lets rust get a foothold on the leaves.
Feeding
Feed it lightly in spring with a balanced fertilizer or a thin layer of compost, and leave it at that. Soil that's too rich just pushes out soft growth that flops and wrecks the upright look you wanted in the first place.
Pruning
There's really just one cut all year. Shear the whole clump down to a few inches above the ground in late winter or very early spring, before the fresh green shoots break, and it'll bounce right back within a few weeks.
Repotting
Out in the ground, the job is dividing rather than repotting. Every few years, once the center thins or the clump starts losing steam, dig and split it in spring or fall, hang onto the healthy outer pieces, and toss the dead middle.
Size & spacing
A clump tops out at 3 to 5 feet (91 to 152 cm) tall when it's in flower, all while staying skinny, with a spread of roughly 18 to 30 inches (46 to 76 cm). That tidy footprint is exactly why it shines as a vertical accent or planted in a row.
When to plant
Feather reed grass goes in the ground in spring or fall, back when the soil's still cool and the roots can dig in without summer pushing back. The flower plumes come up in early summer, around June, and then stick around as tan spikes all the way through fall and 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
Almost every hiccup with feather reed grass traces back to one of three things: too much shade, too much summer heat, or a clump that's getting old. The clues are easy to spot once you know what you're looking at. Find your symptom below, then make the one change that sorts it out.
Powdery orange spots that smear when you touch them
Those rusty bumps? That's rust disease, and it tends to crop up after a long wet stretch or hot, soggy weather. Pull off the worst leaves, thin the clump so air can flow through it, and try to keep the foliage dry. Then clear out anything infected when you do the late-winter cutback so it can't linger into next year.
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
An empty, dead spot opening up in the middle
An older clump tends to go hollow in the middle while the outer ring keeps right on growing, and that's just the plant telling you it's time to split it. Lift it in spring or fall, replant the strong outer chunks, and chuck the dead center. Do this every few years and it stays nice and full.
Fix:
- Dig and divide the clump in spring or fall
- Replant healthy outer divisions and discard the dead center
Worn-out, browning leaves once the summer heat hits
Here's the thing: this is a cool-season grass, so it puts on most of its growth in spring and fall and tends to coast when summer gets hot and sticky, especially down South. So don't reach for the shears in a panic. Just keep it watered through the worst of it, and it'll green right back up once things cool off.
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
Stems sprawling instead of standing up straight
When that nice vertical shape goes floppy, you can usually blame too much shade or soil that's too rich. Shift the clump into full sun and back off the feeding. Believe it or not, leaner conditions are exactly what keep the stalks bolt upright.
Fix:
- Transplant to a full-sun location
- Reduce fertilization and avoid overly rich soil
Toxicity
This one's an easy roommate. Feather reed grass is non-toxic and isn't on the ASPCA poison lists, so it's safe around cats, dogs, and everyone else in the house. The only real gotcha is physical: the blades and seed heads have sharp edges that can scratch, and a pet that wolfs down a mouthful of grass might bring it right back up.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
Totally fine to have around. If a cat chomps a blade, it might hack it back up like it would with any grass, but there's nothing poisonous in it to worry about.
Dogs Safe
No toxins to speak of, so a dog can sniff and nibble all it wants. Worst case, you'll see a bit of vomiting after it swallows a big mouthful of grass.
Horses Safe
Not flagged as a worry for horses. The only thing to watch is those stiff, sharp blades, which can scratch as they brush past.
Rabbits Safe
Nothing here will hurt a rabbit. The leaves are coarse and sharp-edged though, so it's hardly a tasty snack, and they usually steer clear of it anyway.
Livestock Safe
Cattle, goats, and sheep can graze right alongside it without getting poisoned. It's grown to look good rather than to feed anything, so they tend to ignore it.
Birds Safe
Harmless to birds, and they'll happily peck at the seed heads. Mind you, the popular forms are sterile, so there isn't much seed for them to find.
People Safe
No danger to people at all. Just slip on gloves before you cut it down, since the leaf edges and seed spikes 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
Just a handful of named forms cover nearly every feather reed grass you'll run into at the garden center. Here are the ones worth knowing by name.
Karl Foerster
The original upright sterile hybrid, and the one that took home Perennial Plant of the Year in 2001. It pairs green blades with tan vertical plumes, and it won't sow itself around.
Overdam
A shorter variegated pick, roughly 3 feet tall, with green leaves that are trimmed in crisp white stripes along the edges.
Avalanche
Another variegated option, reaching close to 4 feet, but here the white shows up as a wide stripe running right down the middle of each leaf.
Calamagrostis brachytricha (Korean feather reed grass)
A warm-season relative that grows in a looser, arching mound and puts out pinkish plumes that open up in late summer and fall.
How to propagate
Since the popular forms are sterile, you make more feather reed grass by splitting a clump instead of sowing seed. It's the very same easy job that keeps an old plant looking young.
DivisionEasy
Spring or fall · One growing season
Splitting is how you make more feather reed grass, and it pulls double duty as the fix for an old clump that's gone hollow in the middle. Lift an established plant in spring or fall, divide it up, replant the good outer pieces, and they'll get going over a single growing season.
SeedDemanding
Not applicable for sterile cultivars · Not applicable; sterile cultivars set little or no viable seed
Seed just won't work for the cultivars most folks grow. Sterile hybrids like Karl Foerster set little or no viable seed, so there's basically nothing to plant, and trying to start the named forms from seed isn't worth the bother.
Myths
All ornamental grasses self-seed and take over the garden.
Not so with the popular feather reed grass forms, Karl Foerster included. They're sterile and set little or no viable seed, which means they stay right where you plant them and never scatter themselves around. So the standard cultivars are well-behaved and non-invasive. Sure, the wild species and the rare stray seedling can spread, but the hybrids you actually buy won't.