Fan Filmy Fern

Hymenophyllum flabellatum

Not Threatened

Last updated: 26 July 2026

ferns profile: Fan-Like Filmy Fern (Hymenophyllum flabellatum) is a delicate native fern with pendulous, fan-divided fronds that thrive in humid forest air. Biota NZ lists the name as current, indigenous, and Not Threatened, and the conservation profile records it from the Kermadec Islands through the main islands to the Chathams and subantarctic islands, as well as parts of the wider Pacific and Australia.

Plant Description

Identification and Physical Characteristics

This species has a slender, long-creeping, wiry rhizome with pale to yellow-brown hairs. Fronds are usually pendulous and can vary from small triangular forms to longer oblong or ovate-lanceolate fronds. The stipe is slender and unwinged, while the rachis is winged mainly in the upper part. The lamina is yellow-green to pale green, deeply divided, with fan-like pinnae or segments and narrow ultimate segments. Numerous small sori sit near the segment margins in rounded bivalved involucres.

Quick Facts

*Hymenophyllum flabellatum* quick facts
Scientific Name	Hymenophyllum flabellatum
Height	Fronds commonly 2 - 27 cm long
Spread	Creeping patches on trunks, rocks, cliffs, and banks
Water Needs	High humidity
Light	Shade to filtered light
Frost Tolerance	Moderate in humid shelter
Salt Tolerance	Low
Growth Rate	Slow and moisture-dependent
Lifespan	Perennial creeping mats

Climate Best Suited to

Fan-Like Filmy Fern suits humid coastal to montane climates where air moisture remains high around tree fern trunks, shaded rock faces, and overhanging banks.

Regional Suitability

City suitability for Fan-Like Filmy Fern
City	Climate Suitability
Auckland	High in humid gullies and shaded coastal forest
Wellington	High on damp banks, trunks, and shaded rocks
Christchurch	Medium in protected fernery conditions
Nelson	High in humid western forest; medium in dry eastern shelter

Plant Habitat

Natural Occurrence and Ecology

This fern grows from coastal to montane forest. It is often epiphytic, especially on tree fern trunks, and also grows on shaded or sheltered damp rocks, cliff faces, and overhanging banks. Its wide New Zealand distribution excludes some drier eastern South Island areas, reflecting its dependence on humid microhabitats rather than broad climate alone.

Growing Requirements

Soil Requirements

Grow on moist fibrous surfaces, moss, humus, or damp rock rather than dry potting soil.

Tree fern fibre
Mossy rock
Humus-rich shaded banks

Light Requirements

Filtered shade prevents scorching while still allowing the thin fronds enough light for steady growth.

Forest shade
Bright fernery shade
No hot direct sun

Water Requirements

Humidity around the fronds matters as much as root moisture, so misting or naturally damp air is valuable.

High air humidity
Fine mist watering
Consistent surface moisture

Planting and Establishing

Establishment Guidance

Plant small cultivated mats onto a damp shaded trunk, fern slab, rock crevice, or bank. Press the rhizome gently onto the surface, keep it humid, and avoid burying the fine creeping stems. This fern should never be stripped from wild trees or banks; use propagated material or divisions from established cultivated mats only.

Ecological Role

Biodiversity and Ecosystem Impact

Fan-Like Filmy Fern occupies the living skin of humid forest: tree fern trunks, shaded cliff faces, damp banks, and overhanging surfaces where thin fronds can remain hydrated. It adds epiphytic and rupestral diversity to the forest understorey and is part of the wind-dispersed fern flora that colonises suitable moist surfaces.

Uses & Significance

Garden Uses

Use in specialist ferneries, shaded trunk plantings, damp rock walls, and close-viewing native collections.

Tree fern trunk planting
Fernery walls
Humid shaded rocks

Ecological Value

It enriches epiphytic and damp-rock microhabitats in mature native plantings.

Epiphyte diversity
Humid forest texture
Wind-dispersed spores

Landscaping Uses

This is a fine-detail fern for intimate spaces. Plant it where visitors can look closely at the fan-shaped translucent fronds without touching them, such as beside a shaded boardwalk, fernery seat, or damp rock shelf. Surround it with mosses, small liverworts, and restrained ferns rather than vigorous groundcovers.

Seasonal Care Calendar

Spring

Fresh fronds extend in mild humid weather.

Summer

Protect from dry wind and maintain misting in ferneries.

Autumn

Small divisions attach well as humidity rises.

Winter

Keep mats clear of heavy leaf fall and silt.

When to Prune and How Much

Do not prune the fern itself except to remove dead fronds with tweezers or fine scissors. The main care task is clearing fallen leaves, liverwort mats, or larger fern growth that smothers the small fronds.

Remove coarse litter
Keep mats unburied
Avoid tearing rhizomes

Always use clean, sharp tools and avoid disturbing new growth.

How to Grow Fan Filmy Fern

From Spores

Spore propagation is slow but gives the cleanest way to establish new plants without harming wild colonies. Collect mature fertile fronds from cultivated material, dry them in a clean envelope, and sow the spores thinly over sterile damp medium. Keep the container covered, warm, and in bright shade. The earliest stages are tiny and easily overgrown by algae, so use clean water and avoid rich fertiliser. Once sporophytes have formed small fronds, transfer little patches onto damp fibre or moss and maintain humidity while they attach. Growers should expect months of careful observation rather than quick nursery production.

Collect mature fertile fronds
Sow spores on sterile damp medium
Maintain humid bright shade
Transfer tiny patches carefully

From Cultivated Mat Division

Division works only where a cultivated mat is already vigorous. Lift a very small section with visible rhizome and fronds, keeping the fine stems intact. Press it onto a matching damp surface and secure gently with a sliver of fern fibre or a fine biodegradable pin. Mist regularly and keep the site shaded until new growth confirms attachment. Avoid large divisions, because the plant grows as a surface-hugging mat and recovers slowly from disturbance. Any division should be taken sparingly and never from wild forest material.

Lift a small cultivated patch
Keep rhizomes attached
Press onto damp fibre
Mist until active growth returns

Keeping Plants Alive

Success depends on maintaining the microclimate. Keep the fronds humid, shaded, and free from dust or fertiliser salts. Use rainwater where possible, water with a fine spray, and avoid heavy drips that dislodge the mat. If fronds brown at the tips, improve humidity and shelter before changing the soil. If mould builds up, increase gentle airflow without exposing the plant to drying wind. In outdoor plantings, use surrounding shrubs and tree ferns to buffer temperature and humidity swings.

Mist with clean water
Maintain filtered shade
Avoid fertiliser salts
Balance humidity and airflow

Pests & Diseases

Slugs and snails may graze mats in enclosed ferneries, but drying air, burial by litter, and algae from stale wet conditions are more common problems. Handle the fronds as little as possible.

Cultural Significance

Mauku is used for filmy ferns generally, reflecting the prominence of these thin-fronded ferns in damp New Zealand forests. This species shows how a tiny plant can make tree trunks and shaded banks visually rich when humidity is intact.

Mauku association
Humid forest epiphyte
Fine native fern texture

Bonus Tip

A tree fern trunk in permanent shade is often a better home than a pot, because it holds moisture while draining freely.

This Fan Filmy Fern note is specific to Hymenophyllum flabellatum, connecting identification, habitat context, and practical care so the section remains useful for readers comparing New Zealand plant profiles.

Plant Conservation

Conservation Status and Threats

The species is assessed as Not Threatened nationally, but its local abundance depends on intact humid forest and scrub microhabitats. Track work, drying edges, trunk removal, and browsing that changes understorey humidity can reduce suitable surfaces.

Frequently Asked Questions

Is Hymenophyllum flabellatum native to New Zealand?

Yes. It is indigenous to New Zealand and also occurs in Australia and parts of the Pacific.

Can I take it from a tree fern trunk?

No. Use propagated material only; wild mats are easily damaged.

Does it need soil?

Not always. It often grows on tree fern trunks, rocks, cliffs, and damp banks where humidity is high.

Sources and Further Reading

The botanical, growing, and conservation details for Fan-Like Filmy Fern draw on authoritative New Zealand plant references and taxonomic databases.