By the HMNDP Editorial Team. Last reviewed: June 2026.
What is feather reed grass?
Feather reed grass is an upright, clumping ornamental grass in the genus Calamagrostis, most often the hybrid Calamagrostis x acutiflora. It grows narrow and vertical, 3 to 5 feet tall, with feathery flower plumes that emerge in early summer and hold their shape into winter. It is a cool-season perennial hardy in USDA zones 4 to 9, prized as a vertical accent in borders and mass plantings.
The dominant variety is the cultivar ‘Karl Foerster’, a sterile hybrid. Because it sets no viable seed, it stays put and does not spread, which separates it from the seed-producing Korean species discussed below.
The genus name Calamagrostis comes from the Greek for “reed grass,” which is why the common and botanical names line up so closely. When a label says feather reed grass, it almost always means Calamagrostis x acutiflora ‘Karl Foerster’ unless a specific cultivar is named.
Botanical identity: Calamagrostis x acutiflora and the genus
Calamagrostis x acutiflora is a natural hybrid between two European grasses, Calamagrostis epigejos and Calamagrostis arundinacea. The genus Calamagrostis holds roughly 250 species worldwide. For gardeners, three plants cover nearly all ornamental use: the hybrid ‘Karl Foerster’, the variegated sport ‘Overdam’, and the Korean species Calamagrostis brachytricha.
The hybrid is cool-season, meaning it pushes new green growth early in spring while warm-season grasses are still dormant. It flowers earlier than most ornamental grasses, often by June, giving it a long display window.
Karl Foerster: the dominant cultivar
‘Karl Foerster’ is the benchmark feather reed grass and the 2001 Perennial Plant of the Year, named by German nurseryman Karl Foerster. It reaches 4 to 5 feet in bloom on a tight 18 to 24 inch wide clump, stays strictly vertical without flopping, and is sterile so it never self-seeds. Plumes open pinkish-bronze in June and fade to wheat-gold by late summer.
Its strict upright form is the reason it shows up in so many commercial and residential designs. It reads like an exclamation point, holding a line in a border or hedge-row planting where wider grasses would sprawl.
Because it is a sterile triploid hybrid, the only way to make more is by division, not seed. That sterility is a feature for most buyers: no volunteer seedlings, no spread into beds or wild areas.
Korean feather reed grass: a softer alternative
Korean feather reed grass (Calamagrostis brachytricha) is a separate species, not a cultivar of the hybrid. It grows 3 to 4 feet tall with broader, more arching foliage and tolerates more shade than ‘Karl Foerster’. It blooms later, in late summer to fall, with diffuse, feathery, pinkish plumes that look more open and airy than the tight spikes of the hybrid.
The trade-off: C. brachytricha is fertile and produces viable seed, so it can self-sow and spread in favorable sites. If you want a fill-and-forget grass for shadier ground and do not mind some volunteers, it fits. If you want zero spread, choose the sterile hybrid.
Cultivar comparison: Karl Foerster vs Overdam vs Korean
The fastest way to choose is to compare the three common feather reed grasses on the traits that actually drive a planting decision: height, sun tolerance, bloom timing, and whether the plant spreads. The table below puts them side by side, which no single nursery page does.
| Trait | ‘Karl Foerster’ | ‘Overdam’ | Korean (C. brachytricha) |
|---|---|---|---|
| Botanical name | C. x acutiflora | C. x acutiflora | C. brachytricha |
| Height in bloom | 4 to 5 ft | 3 to 4 ft | 3 to 4 ft |
| Foliage | Solid green | White-and-green variegated | Green, broader, arching |
| Light | Full sun, light shade | Full sun to part shade | Part shade tolerant |
| Bloom time | Early summer (June) | Early summer | Late summer to fall |
| Habit | Strictly upright | Upright | Upright, arching plumes |
| Seed / spread | Sterile, no spread | Sterile, no spread | Fertile, can self-seed |
| Zones | 4 to 9 | 4 to 9 | 4 to 9 |
‘Overdam’ is essentially ‘Karl Foerster’ with variegated foliage and slightly shorter, slightly less heat-tolerant growth. Pick it for the brighter foliage; pick the straight ‘Karl Foerster’ for maximum height and toughness; pick Korean for shade and a later, softer bloom.
Does feather reed grass spread or become invasive?
The sterile hybrids ‘Karl Foerster’ and ‘Overdam’ do not spread by seed and are not considered invasive. They expand only by slowly widening their crown, a few inches per year, and are easy to contain by division. The fertile Korean species can self-sow, so it has a low but real spread risk in mild, moist climates.
This sterility point is the single most useful buying fact, and almost no product page states it plainly. If a neighbor’s Calamagrostis “took over,” it was likely a seed-grown fertile type, not the hybrid. For mass plantings near natural areas, the sterile ‘Karl Foerster’ is the safe default.
How to plant feather reed grass
Feather reed grass plants in spring or early fall in full sun to partial shade, in moist but well-drained soil. It tolerates clay and a range of pH, and once established it handles brief dry spells. Space plants 18 to 24 inches apart for a clean row, or 24 to 30 inches for individual specimens.
- Dig a hole twice as wide as the root ball and the same depth.
- Loosen the roots if they circle the pot, then set the crown level with the soil surface.
- Backfill, firm gently, and water deeply to settle the soil.
- Water weekly for the first season while roots establish.
- Add 2 to 3 inches of mulch, keeping it off the crown.
Full sun gives the strongest vertical stems. In shade beyond about 4 hours of direct sun, the hybrid stretches and can lean. For consistent results, match your soil with a balanced feeding program; see our guide to the best fertilizer for grass for product types and timing.
When and how to cut back feather reed grass
Cut feather reed grass back once a year in late winter or early spring, before new green growth pushes up, usually February to early April depending on your zone. Cut the whole clump down to 4 to 6 inches above the ground using hedge shears or a string trimmer. Doing it before regrowth keeps the new blades from being sheared and browned.
Leave the dried plumes and stems standing through winter. They provide structure, catch frost and snow, and give birds cover and seed. Cutting too late, after green shoots appear, leaves blunt brown tips all season.
One quirk to plan for: this is a cool-season grass, so it greens up early, blooms in early summer, then can look tired or partly brown during the hottest weeks. That midsummer fade is normal, not a disease. Steady moisture reduces it; in drought-prone beds, our notes on the best garden fertilizer for drought cover keeping ornamental plantings resilient through heat.
How to divide and propagate feather reed grass
Divide feather reed grass every 3 to 4 years in early spring, when the clump’s center thins or dies out or when you want more plants. Division is the only reliable way to propagate the sterile hybrids, since they set no viable seed. Dig the whole clump, slice it into fist-sized sections with a sharp spade, each with roots and growing points, and replant promptly.
- Lift the entire clump with a spade in early spring as growth resumes.
- Cut it into sections, each 4 to 6 inches across with healthy roots.
- Discard the dead woody center if present.
- Replant divisions at the original depth and water in well.
The fertile Korean species can also be grown from collected seed, though seedlings vary. For the hybrids, skip seed entirely.
Landscape uses and where to buy
Feather reed grass works as a vertical accent, a see-through screen, a border backbone, and in mass or drift plantings where its uniform upright lines read as a single sweep. It pairs well with coneflower, black-eyed Susan, sedum, and Russian sage, and its winter plumes carry the bed past frost. Plant in odd-numbered groups of 3, 5, or 7 for the strongest visual rhythm.
It is widely sold at garden centers and through growers such as Monrovia and Walters Gardens, plus regional independent nurseries, usually in 1 to 3 gallon containers in spring. Buy named cultivars (‘Karl Foerster’, ‘Overdam’) by label to guarantee the sterile, non-spreading type. For broader plant selection context, browse our overview of types of grass and the full HMNDP learn library.
Frequently Asked Questions
What is feather reed grass, and is it the same as Calamagrostis?
Yes. Feather reed grass is the common name for ornamental grasses in the genus Calamagrostis, most often the hybrid Calamagrostis x acutiflora and its cultivar ‘Karl Foerster’. It is an upright, clumping, cool-season perennial reaching 3 to 5 feet with feathery summer plumes. The name “reed grass” comes directly from the Greek root of Calamagrostis.
What growing zones is feather reed grass hardy in?
Feather reed grass is hardy in USDA zones 4 to 9, covering most of the continental United States. It tolerates cold winters down to roughly minus 30 degrees Fahrenheit in zone 4 and handles summer heat through zone 9. As a cool-season grass it greens up early in spring and may look tired during peak summer heat before recovering in fall.
How big does feather reed grass get and how fast does it grow?
‘Karl Foerster’ reaches 4 to 5 feet tall in bloom on an 18 to 24 inch wide clump; ‘Overdam’ and Korean feather reed grass stay closer to 3 to 4 feet. It grows quickly, reaching mature size in 2 to 3 seasons from a 1 gallon plant. The clump widens only a few inches per year, so it stays neat and rarely needs containment.
When and how do you cut back feather reed grass?
Cut feather reed grass back once a year in late winter or early spring, before new green shoots emerge, typically February to early April. Shear the whole clump to 4 to 6 inches above the soil with hedge shears or a string trimmer. Leave the dried plumes standing all winter for structure and wildlife, then remove them in this single annual cut.
Does feather reed grass spread or self-seed?
The hybrid cultivars ‘Karl Foerster’ and ‘Overdam’ are sterile and do not self-seed or spread; they only widen their crown slowly and are not invasive. Korean feather reed grass (Calamagrostis brachytricha) is fertile and can self-sow in mild, moist climates. For zero spread, choose a named sterile hybrid rather than a seed-grown species.
What is the difference between Karl Foerster and Korean feather reed grass?
‘Karl Foerster’ (C. x acutiflora) is a sterile hybrid that grows 4 to 5 feet, strictly upright, blooms in early summer, and prefers full sun. Korean feather reed grass (C. brachytricha) is a separate fertile species, 3 to 4 feet, with broader arching foliage, more shade tolerance, and softer late-summer plumes that can self-seed.
Does feather reed grass grow in shade or need full sun?
Feather reed grass grows best in full sun, which keeps stems strong and strictly vertical. ‘Karl Foerster’ tolerates light or partial shade with at least 4 hours of direct sun but may lean or stretch in deeper shade. Korean feather reed grass handles partial shade better, making it the preferred choice for shadier borders and woodland edges.
How do you divide and propagate feather reed grass?
Divide feather reed grass every 3 to 4 years in early spring as growth resumes. Lift the whole clump, cut it into fist-sized sections each with roots and shoots, discard any dead center, and replant at the original depth. Division is the only reliable propagation method for the sterile hybrids, since ‘Karl Foerster’ and ‘Overdam’ set no viable seed.