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Blechnum nudum

fishbone water-fern

Blechnaceae Southeastern Australia

Container Friendly

SunPart Shade – Full Shade

WaterHigh

HardinessZones 9–10

Overview

Blechnum nudum is an evergreen water-fern native to southeastern Australia, growing in shaded, moist gullies, along creeks, and in wet forest. It forms a crown of arching fronds atop a short, erect rhizome that can build into a slender trunk-like base up to about 12 inches (30 cm) tall with age. The fronds are once-divided in a regular comb or fishbone pattern, 1-3 feet (30-90 cm) long, with new growth flushing pink to reddish before turning green. Two kinds of fronds are produced: broad, spreading sterile fronds and narrower, stiffly erect fertile fronds held in the centre, which carry the spore cases in continuous lines along the segments. Being a fern, it reproduces by spores rather than flowers. It needs constant moisture and shade, and it browns quickly if allowed to dry out or sit in hot sun. In suitable damp, sheltered spots it forms spreading colonies from creeping rhizomes. It is frost-sensitive in exposed positions but tolerates light frost under a forest canopy.

Native Range

Native to southeastern Australia, including New South Wales, Victoria, Tasmania, and South Australia. It grows along shaded creeks, in moist gullies, and in wet sclerophyll and fern forest on damp, acidic soils.

Suggested Uses

Blechnum nudum is used in shaded, moist gardens, fernries, and along ponds and watercourses, and for understorey planting beneath taller trees. It suits damp courtyards and bog-garden edges in frost-protected positions. Grown in groups it forms a soft green colony in deep shade.

How to Identify

Recognised by its fishbone-patterned, once-divided fronds, its short erect trunk-like base in older plants, and its pink to red new growth. The narrow, stiffly erect fertile fronds stand in the centre of the crown, distinct from the broader spreading sterile fronds. Continuous lines of spore cases run along the underside segments of the fertile fronds.

Appearance

Size & Dimensions

Height1' - 3'

Width/Spread2' - 4'

Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Ferns do not flower; Blechnum nudum reproduces by spores. Spore cases form in continuous lines along the narrow fertile fronds, mainly through the warmer months. Ripe spores are shed and dispersed by wind and water.

Detailed Descriptions

Foliage Description

Green, pink to red when new

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Shade

Requires 1-4 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

loam peat

Drainagemoist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

3-5 years

Care & Maintenance

Care Guide

Blechnum nudum grows in shade to part shade in constantly moist, acidic soil rich in organic matter, in keeping with its natural creek-side habitat. It does not tolerate drying out and browns in hot sun or dry wind. Steady moisture, shelter, and humidity keep the fronds fresh, and a mulch of leaf litter suits the shallow roots. In containers it needs a free-draining but moisture-retentive mix and regular water. Light frost is tolerated under cover, but exposed plants are damaged by hard frost. Old or browned fronds can be removed to keep the crown tidy.

Pruning

Pruning is limited to cutting away old, browned, or damaged fronds at the base as they age. The central growing crown is left intact, as damage there can set the plant back. Removing spent fronds in late winter makes way for the new pink growth.