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Arrhenatherum elatius

tall oat grass

Poaceae Europe, North Africa, western Asia

SunFull Sun – Part Shade

WaterMedium

HardinessZones 4–8

Overview

Arrhenatherum elatius, false oat-grass, is a tall, tussock-forming perennial grass in the family Poaceae, growing 24-72 inches (60-180 cm) tall in loose clumps. The flat, grey-green leaf blades are rough to the touch, and the stems rise well above the foliage to carry the flower heads. From late spring into summer it produces open, nodding panicles 4-12 inches (10-30 cm) long, shining green tinged with purple, the spikelets bearing slender bent awns that catch the light. It grows in rough grassland, road verges, hedge banks, railway sides, and meadows on most fertile soils, and is a dominant grass of ungrazed lowland verges. A form with a chain of swollen, onion-like corms at the stem base, known as onion couch, spreads from these corms and persists as a difficult weed in cultivated ground. The plant is wind-pollinated and sets abundant seed, dispersing widely along disturbed corridors. It dies back to the tuft over winter and regrows in spring. Coarse growth and free seeding can let it crowd out smaller grasses and wildflowers in unmanaged grassland.

Native Range

Native to Europe, North Africa, and western Asia, where it grows in meadows, rough grassland, scrub edges, and along tracks and verges on a wide range of soils. It has naturalized across North America, Australia, and other temperate regions, where it is often regarded as invasive.

Suggested Uses

Grown in wildflower meadows, naturalistic grassland, and conservation plantings where a tall, airy grass structure is wanted. Used for erosion control and quick cover on banks, verges, and disturbed ground. Its coarse growth and free seeding make it unsuited to small borders or managed ornamental lawns.

How to Identify

Look for a tall, loosely tufted grass with grey-green, slightly rough leaves and airy, nodding flower heads in early summer. The shining green-and-purple spikelets each carry a long, bent awn, giving the panicle an open, oat-like look. A swollen string of corms at the stem base marks the onion-couch form of Arrhenatherum elatius, separating it from true couch grasses with creeping rhizomes.

Appearance

Size & Dimensions

Height2' - 6'

Width/Spread1' - 2'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Spring Summer

The grass flowers from May through July, the panicles opening loose and nodding as the awned spikelets mature. Pollen is shed to the wind, with no scent or nectar to draw insects. Ripe seed falls through summer and is carried along verges and disturbed ground.

Detailed Descriptions

Foliage Description

grey-green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 5-9 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 Range5.5 - 7.8(Neutral)

357912

Soil Types

loam clay chalk sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

1-2 years

Care & Maintenance

Care Guide

Growth is strongest in full sun to light shade on moist, fertile, well-drained soil, though the grass tolerates poor and dry ground once established. It needs no watering except in prolonged drought and no feeding, as rich soil only increases its bulk. In borders the clumps are cut back in late winter before new growth begins. Free self-seeding spreads it quickly, so flower heads are removed before the seed ripens where spread is unwanted. The onion-couch form regrows from its basal corms, and clearing it means lifting the corms rather than cutting the tops. The tuft regrows each spring from the crown.