Phalaris arundinacea, reed canary grass
1 / 4
Grass

Phalaris arundinacea

reed canary grass

Poaceae

Circumboreal (Europe, Asia, North America — native genotypes exist in North America but invasive Eurasian cultivars dominate)

At a Glance

TypeGrass
HabitUpright
FoliageDeciduous
Height36-84 inches (90-210 cm)
Width24-60 inches (60-150 cm)

Growing Zones

USDA Hardiness Zones

3 - 9
Zone 3
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Native to North America
Maintenancehigh

Overview

Phalaris arundinacea is a robust, rhizomatous perennial grass in the grass family (Poaceae) reaching 3–7 feet (0.9–2.1 m) tall with a 2–5 foot (0.6–1.5 m) spread, forming dense, monoculture stands in wetlands and riparian areas. Stems (culms) are erect, stout, smooth, hollow, with 3–5 nodes. Leaves are flat, blue-green, 0.3–0.8 inch (8–20 mm) wide, rough on the margins, with a distinctive gradual taper. The ligule is membranous, 0.2–0.4 inch (5–10 mm) long, rounded, often torn. Panicles are compact, 3–8 inches (8–20 cm) long, erect, dense, green to purplish at flowering, becoming open and tan at maturity. Spikelets are one-flowered with two sterile lemmas at the base of the fertile floret (diagnostic for Phalaris). Rhizomes are thick, creeping, forming dense mats that exclude other vegetation. A single stand can expand 3–6 feet (0.9–1.8 m) per year via rhizomes. Both native North American genotypes and introduced Eurasian forage cultivars exist; the invasive populations in the Pacific Northwest are predominantly of Eurasian origin, selected for vigor and persistence as forage. Listed as a Class C noxious weed in Washington State. The single most dominant invasive species in Pacific Northwest wetlands, converting diverse emergent marshes to dense monocultures.

Native Range

Circumboreal distribution: native genotypes occur in North America, Europe, and Asia. The invasive populations in the Pacific Northwest are predominantly Eurasian cultivars introduced for forage and erosion control beginning in the 1800s. These cultivars are more vigorous and competitive than native genotypes. Occurs in wet meadows, marshes, stream margins, floodplains, and ditches from sea level to approximately 6,500 feet (2,000 m). Dominates more wetland acreage in the Pacific Northwest than any other single invasive species.

Suggested Uses

Used as the primary case study in Pacific Northwest wetland restoration for teaching the challenges of rhizomatous grass invasion. The native versus introduced genotype question is studied in invasion genetics. Studied in wetland hydrology (the dense rhizome mat alters water flow and sediment deposition), wildlife habitat conversion (reduces habitat for ground-nesting birds and amphibians), and long-term restoration planning. The forage cultivar introduction history is a standard case in unintended consequences of agricultural introductions.

How to Identify

Distinguished from other large wetland grasses by the compact, dense panicle (versus the large, open, plume-like panicle of Phragmites australis), the blue-green leaf color, the relatively narrow leaves 0.3–0.8 inch (8–20 mm) wide (versus leaves up to 2 inches / 5 cm wide in Phragmites), and the spikelets with two sterile lemmas below the fertile floret. The membranous ligule and rough leaf margins are useful vegetative characters. The dense, rhizomatous colony-forming habit is shared with Phragmites but Phalaris stands are shorter (3–7 feet versus 6–15 feet).

Appearance

Size & Dimensions

Height3' - 7'
Width/Spread2' - 5'

Colors

Flower Colors

green
purple

Foliage Colors

green
gray

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

~3 weeks
J
F
M
A
M
J
J
A
S
O
N
D
SpringSummer
Flowers from May through July. Compact panicles emerge green to purplish and become open and tan as seeds mature over 2–3 weeks. Wind-pollinated. Seeds mature by July in the Pacific Northwest. Seed viability is variable; vegetative spread via rhizomes is the primary expansion mechanism.

Detailed Descriptions

Flower Description

Green to purplish, becoming tan at maturity

Foliage Description

Blue-green to medium green, flat, rough-textured blades 0.3-0.8 inch (8-20 mm) wide with a distinctive gradual taper to the tip

Growing Conditions

Sun Requirements

Full Sun
Partial Shade
Requires 4-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 8.0(Neutral)
357912
Soil Types
loamclaysiltpeat
Drainage
moist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

1-2 years

Care & Maintenance

Care Guide

Listed as a Class C noxious weed in Washington State; one of the most difficult wetland weeds to manage. Mowing or cutting reduces above-ground biomass but does not kill the rhizome network. Repeated mowing 3–5 times per growing season for 3–5 years gradually depletes rhizome reserves. Solarization with black plastic sheeting during summer (June–September) over mowed stands kills rhizomes in the top 6 inches (15 cm) of soil. Excavation of the rhizome mat is effective for small areas but labor-intensive. Revegetation with native wetland species (sedges, rushes, native grasses, willows) immediately after removal is essential to prevent re-establishment. The species tolerates prolonged flooding, seasonal drought, and nutrient-poor conditions, making site manipulation alone insufficient for control.

Pruning

No pruning applicable. Stands are mowed or cut at ground level repeatedly during the growing season to deplete rhizome reserves. Cutting 3–5 times between May and September prevents seed set and progressively weakens the root system over 3–5 years.

Maintenance Level

high

⚠️ Toxicity Warning

Non-toxic