Piripiri

Hymenophyllum sanguinolentum

Not Threatened

Hymenophyllum sanguinolentum , commonly known as Piripiri or the Sanguinolent filmy fern, is a fascinating and highly characteristic native fern of New Zealand. This member of the Hymenophyllaceae family is celebrated for its ability to form dense, dark green mats over forest logs, rocks, and the trunks of forest trees. It is uniquely distinguished among New Zealand's many filmy ferns by its strong, metallic aroma - often described as reminiscent of dried blood or wet iron - which is particularly noticeable when the fronds are crushed or dry. Found throughout the country, from the Three Kings Islands to Stewart Island, it is a specialist of humid forest environments. Classified as "Not Threatened," it is one of the most drought-resistant filmy ferns, making it a hardy representative of this delicate group. Its intricate, multi-pinnate fronds add a layer of deep texture and ancient mystery to the shaded floors and canopies of New Zealand's rainforests.

Close-up of the delicate, translucent fronds of Hymenophyllum sanguinolentum — Image credit: Piripiri (*Hymenophyllum sanguinolentum*) - photo by Wikipedia

Plant Description

Piripiri is a small terrestrial or epiphytic fern that grows from a long-creeping, slender rhizome. It typically forms expansive, interwoven mats that can cover large sections of their host surface. The fronds are a deep, dark green and typically range from 5 to 25 cm in length, occasionally reaching up to 30 cm in very sheltered, wet sites. The fronds are ovate to elliptic in overall shape and are deeply divided (3-4-pinnate), giving them a fine, almost lace-like appearance.

The stipes (leaf stalks) are slender, dark brown or black, and notably winged along most of their length. A key identifying feature is the aromatic nature of the fronds, which emit a distinctive, sharp scent. The reproductive structures (sori) are produced on short branches in the upper part of the frond. Each sorus is protected by an indusium that is ovoid-elliptic and features 3 to 5 longitudinal ridges on its outer surface - a detail that helps botanists distinguish it from other similar species. The plant's ability to curl its fronds tightly during dry periods allows it to survive in habitats that would be too harsh for most other filmy ferns.

Quick Facts

Plant Specifications

*Hymenophyllum sanguinolentum* quick facts
Scientific Name	Hymenophyllum sanguinolentum
Family	Hymenophyllaceae
Height	5-30 cm
Growth Form	Mat-forming terrestrial or epiphytic fern
Foliage	Dark green, multi-pinnate, aromatic translucent fronds
Spores	Sori at frond tips; ridges on indusia
Light	Deep to partial shade
Soil	Not applicable (grows on organic debris, logs, or rocks)
Hardiness	Hardy; remarkably drought-tolerant for a filmy fern
Water Needs	High; prefers consistent humidity but handles dry cycles
Spread	Extensive creeping mats
Frost Tolerance	High (protected by forest canopy)
Salt Tolerance	Moderate
Growth Rate	Slow to Medium
Lifespan	Perennial

Climate Best Suited to

Piripiri is exceptionally well-adapted to New Zealand's varied forest climates. It thrives in high-humidity areas but is uniquely capable of surviving the periodic dry spells common in the eastern districts of both islands. It is fully hardy to typical New Zealand winter frosts, especially when growing under the protective canopy of a forest. While it can handle the cool temperatures of the far south, it reaches its greatest abundance in the humid, temperate forests of the North Island and West Coast.

Regional Suitability

City suitability for Piripiri
City	Climate Suitability
Whangārei	Ideal
Auckland	Ideal
Hamilton	Ideal
Rotorua	Ideal
Tauranga	Ideal
Gisborne	Suitable
New Plymouth	Ideal
Whanganui	Ideal
Palmerston North	Ideal
Napier	Suitable (needs high humidity)
Wellington	Ideal
Nelson	Ideal
Christchurch	Suitable (requires shelter/moisture)
Dunedin	Ideal
Invercargill	Ideal

Plant Habitat

The habitat of Hymenophyllum sanguinolentum is one of the broadest among New Zealand ferns. It is found from coastal forest gaps up to the subalpine zone. Its primary habitats include moist, shaded forest floors, the mossy surfaces of rotten logs and stumps, and the shaded faces of rock outcrops and canyon walls. It is frequently an epiphyte, perching on the trunks and branches of a wide variety of forest trees. It is particularly common in areas where environmental stress - such as periodic low humidity or high light - excludes more sensitive filmy ferns. It is a key member of the "epiphytic tapestry" in mature New Zealand rainforests.

Plant Conservation

Piripiri is currently classified as "Not Threatened." It remains one of our most successful and widespread filmy ferns. Its ability to tolerate drought and colonize human-modified habitats like old stone walls ensures its security. However, it still relies on the maintenance of forest fragments and the protection of large-scale forest tracks where it forms its characteristic dense carpets. The primary localized threat is the removal of forest canopies, which leads to a drop in the humidity levels required for its best growth. It is a staple indicator of healthy, regenerating native bush.

Growing Requirements

Substrate Requirements

Does not grow in garden soil. It requires a substrate of organic forest debris, mossy rocks, or rotten wood. In a garden, it must be established on a vertical or textured surface that remains moist.

Mossy rocks or logs
Fibrous tree fern trunks
High organic humus

Light Requirements

Demands deep to partial shade. It is a specialist of the filtered light of the forest understory. While more light-tolerant than other filmy ferns, it will quickly turn brown and crisp if exposed to direct midday sun.

Dappled or deep shade
Cool, sheltered spot
Morning sun only

Water Requirements

Requires high humidity and consistent moisture. While it can survive dry periods by curling its fronds, it needs a return to moisture to thrive. Regular misting in dry weather is highly beneficial.

Constant high humidity
Moist host surface
Tolerates dry spells better than relatives

Planting Guide

Best Planting Practices

Cultivation of Piripiri is best achieved by encouraging its natural spread in a shaded forest-style garden. If you are attempting to establish it, the best method is to transplant a small section of mossy log or rock that already contains the fern rhizomes. Place this in a deep-shade, high-humidity spot - ideally near a pond or a damp gully. It cannot be planted into the ground like a traditional shrub. Ensure the site has good airflow but protection from drying winds. If growing in a conservatory, use a very airy, bark-based mix and provide daily misting. It is strongly advised never to remove large mats from the wild; instead, purchase from a specialist native nursery.

Ecological Role

Environmental Benefits

Piripiri is a vital part of the New Zealand rainforest's moisture management system. Its dense mats act like a sponge, trapping and holding large amounts of water and organic matter high in the canopy or on the forest floor. This creates a nursery environment for countless specialized invertebrates and encourages the growth of beneficial microorganisms. It is a critical component of the forest's multi-layered biodiversity.

Uses & Significance

Garden Significance

A beautiful and sensory choice for specialized forest gardens:

Exquisite textural interest on rocks and logs
Ideal for shaded vertical "living walls"
Unique aromatic feature in a native collection
Essential species for creating a true rainforest feel

Ecological Value

Supports a diverse range of specialized forest-dwelling invertebrates.

Cultural Significance

Traditional Uses and Values

Piripiri is recognized by Māori as an integral part of the forest's life-giving moisture system. While the name "Piripiri" is also used for the unrelated Acaena species (burburs), the filmy fern was valued for its presence in the ngāhere. Today, it is respected as a taonga of our high-humidity forests and a symbol of the intricate beauty of New Zealand's vertical landscapes.

Landscaping Uses

Garden Design Applications

In landscape design, Hymenophyllum sanguinolentum is used to create a sense of ancient, undisturbed lushness. It is the perfect plant for "detailing" a shaded native garden. Massing it over old logs or the base of tree ferns creates a visually stunning, dark green tapestry that softens hard lines. Landscape designers value it for its drought-resistance compared to other filmy ferns, making it a more reliable choice for urban "bush" gardens. Its unique scent also adds a mysterious, atmospheric quality to a shaded walkway or gully.

Seasonal Care

Spring

Ensure high humidity flushes; monitor for new frond emergence; check drainage flushes.

Summer

Regular misting required during dry spells; protect from hot winds; enjoy the dense dark green mats.

Autumn

Spore release period; optimal time for tidy-up of any competing weeds on the host.

Winter

Fully hardy if sheltered; ensure the canopy remains intact for thermal protection.

Pruning

Pruning Techniques

Piripiri requires no pruning. The only maintenance recommended is the gentle removal of any competing exotic weeds or climbing plants that might try to grow through the mat and smother the fern. Dead fronds will eventually turn brown and be incorporated into the organic mat naturally. Always handle the fronds gently to avoid damaging the brittle, translucent tissue.

How to Grow Piripiri

From Spores

Propagation from spores is possible but very slow and requires specialized conditions. Spores should be sown onto a sterilized, moist peat or tree-fern fiber medium. They require consistent humidity and light to germinate into the gametophyte stage. This is rarely successful for the average home gardener.

From Rhizome Divisions

The most effective way to increase your stock. Small sections of the creeping rhizome, each with several fronds and healthy attachment to their substrate, can be carefully moved in autumn or spring. Replant immediately onto a similar mossy or organic surface. Success depends on maintaining very high humidity during the first few months of relocation.

Troubleshooting Common Issues

The most common issue is low humidity leading to frond-curling and browning. If the plant stays curled for too long, it will eventually die - increase misting. Slugs can occasionally target the soft tissue, so monitor carefully. If the plant is turning yellow, it may be receiving too much light or be in stagnant, waterlogged debris. Ensure good air movement and filtered shade.

General Propagation Tips (Seeds & Cuttings)

Successful propagation of native New Zealand plants requires attention to detail and patience. When growing from seed, it is essential to start with fresh, viable seeds collected when they are fully mature. Clean the seeds thoroughly to remove any fleshy pulp, which can inhibit germination. Sow the seeds on the surface of a seed-raising mix that is free-draining yet moisture-retentive. A mix of peat and coarse sand or perlite often works well. Cover the seeds lightly with a fine layer of grit or sieved potting mix, or leave them uncovered if they require light to germinate. Keep the trays in a sheltered, shaded spot and maintain consistent humidity; a plastic cover can help but ensure there is adequate ventilation to prevent fungal diseases. Germination can be erratic, sometimes taking several months, so do not discard the trays too early. For vegetative propagation, semi-hardwood cuttings are often the most successful method for shrubby species. Take cuttings in late summer or early autumn, selecting healthy, non-flowering shoots. Trim them to about 10-15 cm in length, making a clean cut just below a node. Remove the lower leaves and dip the cut end in rooting hormone to encourage root development. Insert the cuttings into a propagating mix, ensuring they are firm and stable. Place them in a humid environment, such as a mist unit or a covered frame, out of direct sunlight. Rooting can take anywhere from a few weeks to several months. Once roots have formed, pot the young plants into individual containers and harden them off gradually before planting out. Division is another effective method for clump-forming plants like sedges, grasses, and lilies. This is best done in autumn or early spring when the plant is actively growing. Lift the clump carefully and tease the roots apart, using two garden forks or a sharp knife if the clump is dense. Ensure each division has a good root system and healthy shoots. Replant the divisions immediately, watering them well to settle the soil around the roots. With proper care, these new plants will establish quickly and grow into healthy specimens. By employing these methods, you can successfully expand your collection of native flora and contribute to the preservation of New Zealand's unique botanical heritage.

Pests & Diseases

Generally very pest-resistant due to its aromatic and leathery nature. Occasionally targeted by slugs or aphids in very sheltered, dry spots. It is notably resistant to the fungal leaf spots that can affect other forest ferns.

Bonus Tip

If you have a shaded, mossy rock wall, "plug" small pieces of Piripiri into the crevices. Over time, it will spread to form a stunning, dark green tapestry that looks like it has been there for centuries.