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Cyperus eragrostis

tall flatsedge

Cyperaceae South America

Deer Resistant Container Friendly

SunFull Sun – Part Shade

WaterHigh

HardinessZones 8–10

Overview

Cyperus eragrostis is a tufted perennial sedge growing 1-3 feet (30-90 cm) tall from short rhizomes, forming dense clumps 12-24 inches (30-60 cm) wide. The three-angled stems are smooth and leafy at the base, with flat yellow-green leaves 0.2-0.4 inch (5-10 mm) wide that often equal or exceed the stems. Each stem is topped by a flower head of densely packed, flattened spikelets clustered into several stalked rays, subtended by leaf-like bracts that spread unevenly. The spikelets ripen from pale green to straw-brown and release many small nutlets. It grows in consistently wet ground along ditches, ponds, streambanks, and seasonal wetlands. Native to South America, it has naturalized across western North America, Europe, Australia, and New Zealand, and behaves as a weed of irrigated and disturbed wet sites. Foliage stays green through mild winters and dies back where hard frost occurs. Its heavy seeding and steady clump expansion can crowd smaller marginal plants.

Native Range

Cyperus eragrostis is native to South America, including the Andes and temperate Chile. It has naturalized widely in western North America, Europe, Australia, and New Zealand along wet, disturbed ground.

Suggested Uses

Used at pond edges, in rain gardens, bog gardens, and damp borders, spaced 18-24 inches (45-60 cm) apart. It stabilizes wet soil along ditches and streambanks. It also grows in containers standing in shallow water.

How to Identify

Identify it by triangular stems topped with rounded clusters of flattened, pale green to straw spikelets held in several stalked rays. Unequal leaf-like bracts spread beneath the head, and the basal leaves are yellow-green and often as long as the stems. The dense, almost spherical spikelet clusters separate it from the looser, brown heads of Cyperus spp. species such as C. esculentus.

Appearance

Size & Dimensions

Height1' - 3'

Width/Spread1' - 2'

Reaches mature size in approximately 1 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~12 weeks

Summer Fall

Flowering runs from summer into autumn, July through October, as flattened spikelets mature in clustered heads. Pollination is by wind, and ripe nutlets shed over a long period. Old straw-brown heads persist on the stems into winter.

Detailed Descriptions

Flower Description

pale green to straw-brown

Foliage Description

yellow-green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-10 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 - 7.5(Neutral)

357912

Soil Types

clay loam silt

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

1 year

Care & Maintenance

Care Guide

Grow in full sun to part shade in wet, fertile soil or at the margins of ponds and bog gardens in standing water up to 2 inches (5 cm) deep. It tolerates clay and seasonally flooded ground and grows fastest with steady moisture. Hardy roughly to USDA zone 8, with foliage evergreen in mild winters and cut down by hard frost. Clumps expand steadily and can be lifted and divided in spring. Self-seeding is heavy in wet ground, so removing spent heads limits spread. No supplemental feeding is needed in moist, fertile soils.

Pruning

Old or frost-damaged stems are cut to the base in late winter before new growth begins. Spent flower heads can be removed through the season to reduce self-seeding. Congested clumps are divided in spring.