Hymenophyllum elongatum

Elongate Filmy Fern

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Taxonomy

Family Hymenophyllaceae · Genus Hymenophyllum

Description

Hymenophyllum elongatum is a delicate filmy fern with paper-thin fronds that shimmer in moisture. A lover of cool, dim forest conditions, it excels in terrariums or shaded vivariums where humidity stays very high and the substrate never dries out.

Common Names

Elongate Filmy FernFilmy Fern

Context

nativeRegion

Temperate rainforests of New Zealand and southeastern Australia (incl. Tasmania).

usdaZones

9–11 outdoors in persistently humid, frost-sheltered microclimates; better indoors/terrarium in most areas.

companionPlants

Trichomanes spp. (filmy ferns), Mosses and liverworts, Selaginella kraussiana, Pleurothallid orchids (e.g., Masdevallia, Pleurothallis), Asplenium bulbiferum (in cool, moist shade)

culturalUses

Primarily ornamental for terraria and cloud-forest displays; valued as an indicator of pristine, humid forest habitats.

Care

Care Requirements

LightDeep to medium shade; bright, indirect light only. No direct sun.

WateringKeep evenly and constantly moist with soft, low-mineral water. Never allow to dry out; avoid waterlogging.

SoilVery airy, moisture-retentive, acidic medium: long-fiber sphagnum with fine bark and a little perlite or leaf mold; or mount on cork/tree-fern fiber with moss.

FertilizerVery dilute (1/8–1/4 strength) balanced fertilizer monthly in spring–summer; flush occasionally to prevent salt buildup.

HumidityExtremely high (85–100% ideal; >70% minimum). Best in a closed terrarium with gentle airflow.

TemperatureCool to mild: 50–75°F (10–24°C). Avoid heat waves (>80°F/27°C) and drying drafts.

Growth & Life Cycle

HabitEvergreen filmy fern with a creeping rhizome; epiphytic or epipetric, forming delicate mats.

Mature SizeFronds typically 5–20 cm long on wiry stipes; slowly spreading rhizome.

Growth RateSlow-growing under stable, high-humidity conditions.

BloomingNo flowers (fern). Produces spores on frond margins when humidity and airflow are optimal.

DormancyNo true dormancy; growth slows in cooler months but remains evergreen if kept moist.

Propagation

MethodsDivision of creeping rhizomes, Spores on sterile, moist medium under sealed high humidity, Tissue culture (advanced)

DifficultyModerate to hard (spore culture is advanced; division is delicate).

Best SeasonSpring to early summer for division; spores whenever conditions are stable and warm.

Maintenance & Notes

PruningMinimal. Snip spent or browned fronds at the base with sterile scissors; avoid damaging the rhizome.

RepottingInfrequent (every 2–3 years). Re-mount or refresh moss when compacted; handle delicately and keep constantly moist during the process.

Pests & DiseasesSensitive to low humidity (frond crisping). Watch for spider mites in dry air, scale, fungus gnats (soggy media), and snails/slugs. Risks: botrytis/rot with stagnant, wet conditions—improve airflow and hygiene.

ToxicityGenerally considered non-toxic to people and pets.

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