1 / 9

Gahnia sieberiana

red-fruit saw-sedge

Cyperaceae Eastern Australia

Attracts Butterflies Container Friendly

SunFull Sun – Part Shade

WaterHigh

HardinessZones 8–11

Overview

Gahnia sieberiana is an evergreen perennial sedge forming a large dense tussock 3-7 feet (1-2 m) tall and 3-6 feet (0.9-1.8 m) wide, with arching leaves that rise and then bend over at the tips. The leaves are long, narrow, and stiff, up to 6 feet (1.8 m) long and about 0.2-0.4 inch (5-10 mm) wide, dull green, with finely toothed, razor-sharp margins that can cut skin. Tall flowering stems extend above the foliage to 6-10 feet (1.8-3 m), bearing dark brown to blackish branched flower heads in spring and summer. The fruit is a hard, shiny nut about 0.1 inch (3 mm) long, ripening red to red-brown. Growth is moderate, and clumps build slowly over several years into broad tussocks that persist for many years. The species tolerates a range of moist to wet soils and partial shade, but the cutting leaf edges and large size limit where it can be placed.

Native Range

Native to eastern Australia, from Queensland through New South Wales and Victoria to Tasmania. Grows in heath, swamp margins, gullies, and wet forest understorey on moist sandy and peaty soils from near sea level to about 3,300 feet (1,000 m).

Suggested Uses

Planted in wetland, bog, and rain-garden plantings, in habitat gardens, and for erosion control on damp banks, spaced 4-6 feet (1.2-1.8 m) apart. It serves as a larval food plant for several native butterflies and shelters small wildlife. The sharp leaf edges and large size limit its use near paths, play areas, and small gardens.

How to Identify

Recognized by the large dense tussock of long arching leaves with razor-sharp, finely toothed margins and by the tall dark brown to blackish flower heads held well above the foliage. The hard shiny red-brown nuts about 0.1 inch (3 mm) long help identify it among the sedges. The cutting leaf edges separate it from softer-leaved grasses of similar size.

Appearance

Size & Dimensions

Height3' - 10'

Width/Spread3' - 6'

Reaches mature size in approximately 5 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~10 weeks

Spring Summer

Flowers in spring and summer, September to February in its native range, though flowering can be irregular and is often heavier after fire. The dark heads persist for many weeks as the nuts ripen from green to red-brown. Seed is held on the stems into autumn.

Detailed Descriptions

Flower Description

Dark brown to blackish

Foliage Description

Dull green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-9 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 Range4.5 - 6.5(Acidic)

357912

Soil Types

sand peat loam

Drainagemoist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

3-5 years

Care & Maintenance

Care Guide

Grows in full sun to part shade in moist to wet sandy or peaty soil and tolerates seasonal waterlogging. Water until established; mature tussocks tolerate short dry spells but stay densest in steady moisture. The leaf margins are sharp enough to cut skin, so the plant is placed away from paths and seating. Old flower stems and dead leaves can be removed once seed has dropped. Few pests affect it, and clumps need little care once settled.

Pruning

Remove spent flower stems at the base after the seed drops to tidy the clump. Old or damaged outer leaves can be cut away, though the sharp margins make handling difficult. Clumps do not need regular cutting back and are slow to recover from heavy division.

Pruning Schedule

fall