Tall Flatsedge

Cyperus eragrostis

WA monitor Cyperaceae

Data Maturity Baseline

Washington State Classification

Monitor List

This plant is on the monitor list.

Quick Reference

Type

perennial herb

Origin

Parts of North and South America

Identification

Growth Habit

Tall flatsedge is a tufted, sedge-like, perennial plant with rhizomes.

Leaves

Leaves are flat or v-shaped, typically 9.8-19.7 inches (25-50 cm) long by 0.2-0.3 inches (5-8 mm) wide. The slender leaves grow from the base of the stem, and about 4-8 involucral leaf-like bracts exceed the inflorescence.

Flowers

Inflorescense is a spherical head of rays of spikelets (usually flat). Rays 3-10 and 1-2 inches (2.5-5 cm) long. Spikelets off-white to golden brown.

Fruit & Seeds

Dark brown to black achene, broadly ellipsoid 1.2–1.4 by 0.5–0.6 mm.

Impact

This plant is on the monitor list. Please contact Sofia Sherman to report locations or for more information.

Ecology & Spread

Habitat

Tall flatsedge grows in damp grasslands, roadsides ditches, vernal pools, streambanks, irrigation channels and also grows in gardens, parks, disturbed sites, waste areas and damp habitats like wetlands.

Spread Mechanisms

seed vegetative fragments

Reproduction

Plants reproduce by seed and vegetatively by rhizomes.

Regional Notes — Puget Sound