Introduction & Discovery

Asplenium bulbiferum is the fern that makes more ferns while you watch. Formally described by Georg Forster in 1776 from specimens collected at Dusky Sound during Captain James Cook’s second voyage to the Pacific (1772–1775), the species epithet bulbiferum — Latin for ‘bulb-bearing’ — refers to the extraordinary reproductive trait that defines this plant: the spontaneous production of miniature plantlets (bulbils) on the upper surfaces of its mature fronds, a phenomenon known as vegetative vivipary. These tiny clones, complete with their own root initials and 2–4 minute fronds, develop directly on the pinnae and rachis of the mother frond, eventually growing heavy enough to weigh the arching blade down to the substrate, where the babies root on contact and establish as independent plants. No spore germination, no gametophyte, no water-dependent fertilisation — just a ready-made sporophyte, handed directly from parent to offspring. This makes A. bulbiferum arguably the easiest fern on Earth to propagate, and certainly the most entertaining. For anyone who has struggled with the arcane patience of spore culture, the mother fern offers instant gratification: detach a plantlet when it has three or four fronds of its own, press it onto moist compost, and watch it root within a week. Beyond its propagation novelty, A. bulbiferum is a genuinely handsome fern in its own right: gracefully arching, finely divided bipinnate to tripinnate fronds reaching 60–120 cm in length, dark green, with an airy lace-like texture that bears absolutely no resemblance to the simple, strap-shaped, undivided fronds of its bird’s-nest relatives A. nidus and A. antiquum. It is one of the most common and conspicuous ground ferns of New Zealand’s native forests, occurring from coastal lowlands to montane bush at 1100 m elevation, and it has been cultivated in European conservatories since the Victorian pteridomania of the 1860s. In Māori culture it is known as pikopiko, mouku, or mauku, and the young unfurling croziers are harvested as a traditional vegetable prized for their asparagus-like flavour.

Discovery & Naming

Asplenium bulbiferum was formally described by Georg Forster (1754–1794), the German-Polish naturalist who accompanied his father Johann Reinhold Forster as draughtsman and assistant on Captain James Cook’s second voyage aboard HMS Resolution (1772–1775). The type specimen was collected at Dusky Sound (Tamatea/Dusky Bay), a deep fiord on the southwest coast of New Zealand’s South Island, where the Resolution anchored for five weeks in March–April 1773 for ship repairs. The lectotype, designated by Brownsey in 1977, is held at the Natural History Museum, London (BM 1048369), labelled ‘Dusky Bay, Messrs Forster.’ Forster published the description in Characteres Generum Plantarum (page 91), the botanical folio he co-authored with his father that appeared in its effective publication in 1776 from the press of P. Elmsly and T. Cadell in London. The book introduced 94 binomial names from 75 genera based on collections from New Zealand, Tahiti, Tonga, and other Pacific islands — the first substantial contribution to New Zealand botany. The epithet bulbiferum is a compound of the Latin bulbus (bulb) and ferre (to bear), a direct reference to the foliar bulbils that Forster observed and which made this fern immediately memorable among the hundreds of plant specimens the Forsters collected during the voyage. The genus name Asplenium derives from the Greek a- (without) + splen (spleen), reflecting the ancient Dioscoridean doctrine of signatures under which spleenwort ferns were prescribed for spleen complaints — a belief carried through European herbals for 1500 years with no pharmacological basis. The species entered European living cultivation during the 1840s–1860s, coinciding with the height of the Victorian fern craze (pteridomania). Its viviparous habit made it a conservatory sensation: growers could distribute young plants to friends by detaching frond-borne babies, earning it the popular name ‘mother fern.’ By 1870 it appeared in most major British and European fern collections, and its ease of vegetative propagation kept the nursery trade supplied without the need for spore culture. However, a taxonomic complication has emerged in the modern era: DNA studies by Perrie, Shepherd, and Brownsey (published 2005) revealed that many plants sold commercially as A. bulbiferum are actually Asplenium × lucrosum — a sterile hybrid between A. bulbiferum and the Norfolk Island endemic A. dimorphum. This hybrid inherited bulbil production from its A. bulbiferum parent but produces malformed, non-viable spores, and it has distinct dimorphic fronds (fertile and sterile fronds differ markedly in segment width). The true species remains common in New Zealand but comparatively rare in the international nursery trade.

Frond Morphology

The fronds of Asplenium bulbiferum are among the most finely divided in the genus, and their architecture represents the polar opposite of the simple, entire blades produced by the bird’s-nest group (A. nidus, A. antiquum, A. australasicum). The lamina is lanceolate to elliptic in outline, 15–120 cm long and 7–30 cm wide, bipinnate to tripinnate, sometimes approaching quadripinnate in the most vigorous specimens growing in deep shade with abundant moisture. The frond bears 15–30 or more pairs of pinnae that are ovate to narrowly ovate, acuminate, shortly stalked, measuring 3–20 cm long by 1–5 cm wide, with basal pairs deflexed (pointing downward when fresh). Secondary pinnae (pinnules) are sessile or shortly stalked, very narrowly elliptic to ovate, obtuse, deeply serrate to almost pinnate, with the basal acroscopic pinnule often enlarged to 40 × 10 mm. Ultimate segments are narrowly oblong, nearly entire to crenate-serrate, up to 10 mm long, giving the whole frond a delicate, lace-like or parsley-like appearance. The stipe is 10–40 cm long, pale green to brown at the base, with scattered dark brown ovate scales that become sparser distally. The rachis is pale green to yellow-green, prominently grooved on the adaxial surface, and bears scattered scales on the underside. The texture of the lamina is herbaceous to thinly coriaceous — softer and more flexible than the leathery blades of A. nidus — and the colour is a rich dark green on the upper surface, slightly paler beneath. The frond’s most distinctive visual feature in cultivation is its arching habit: fronds emerge erect from the rhizome crown, then curve gracefully outward and downward under their own weight, an effect dramatically amplified when bulbils develop on the upper surface and add mass to the distal portions of the blade. A well-grown specimen with multiple fronds bearing clusters of baby plantlets has a cascading, fountain-like silhouette that is immediately identifiable. The weight of the bulbils eventually brings frond tips into contact with the surrounding substrate, at which point the plantlets root in situ — a growth habit that explains the common name ‘hen and chickens,’ with the arching mother frond as the ‘hen’ and the dangling babies as her ‘chicks.’

Native Range & Distribution Map

Distribution map showing the native range of Asplenium bulbiferum.

Biology & Frond Morphology

The defining biological feature of Asplenium bulbiferum is vegetative vivipary — the production of genetically identical plantlets (bulbils) directly on the surfaces of sporophytic fronds, bypassing the entire sexual cycle of spore dispersal, gametophyte development, and syngamy. Bulbils emerge from dormant meristematic tissue at the junctions of pinnae and pinnules along the upper (adaxial) surface of mature fronds, typically appearing first on second-year fronds that have already produced sori on their lower surfaces. Each bulbil begins as a small green bud 2–3 mm across, which rapidly differentiates into a miniature rosette of 2–4 fronds with visible root initials at the base, reaching 3–5 cm before detachment. The bulbils are true sporophytes — diploid clones of the parent, not gametophytes — and they carry the full tetraploid chromosome complement of 2n = 144 (base number x = 36). This ploidy level classifies A. bulbiferum as a tetraploid, which is significant taxonomically because the closely related A. gracillimum is an allooctoploid (2n = 288) formed by hybridisation between A. bulbiferum and A. hookerianum. The vegetative body is organised around a short, erect to sub-erect rhizome 10–20 mm in diameter, densely clothed in dark brown, ovate, acuminate scales 4–8 mm long with entire margins. From this rhizome, fronds emerge in a loose shuttlecock arrangement (not a tight rosette like A. nidus), each consisting of a stipe 10–40 cm long that is green above and dark brown to black at the base, transitioning into a bipinnate to tripinnate lamina 15–120 cm long and 7–30 cm wide. The root system is a mass of dark, wiry adventitious roots that anchor the plant in humus-rich forest-floor substrate. The dual reproductive strategy — sexual (spores) and asexual (bulbils) — is relatively rare among ferns. Among the 700+ species in the genus Asplenium, only a handful exhibit foliar vivipary, including A. daucifolium from the Mascarene Islands and the hybrid A. × lucrosum. The ecological advantage is clear: bulbils can establish immediately in the moist, shaded understorey where spore germination would require months of vulnerable gametophyte growth.

Spore Dispersal

Asplenium bulbiferum possesses a dual reproductive strategy that is uncommon among ferns: it produces both conventional spores through meiotic sporangia and vegetative bulbils through mitotic meristems on the same plant, often on the same frond. The sexual reproductive structures are arranged on the abaxial (lower) surface of fertile fronds in the diagnostic spleenwort pattern: sori are linear, 2–4 mm long, numerous, and positioned along the acroscopic branch of forked veins on the pinnules, running parallel to one another and submarginal in placement. Each sorus is covered by a persistent, narrowly linear indusium attached along the vein on the costal side, opening toward the pinnule margin as sporangia mature. The sori are broad relative to the narrow pinnule segments, and on heavily fertile fronds they can nearly cover the entire abaxial surface of the ultimate segments, giving the underside a distinctly brown, felted appearance. Sporangia are leptosporangiate with the standard annulus-based catapult dispersal mechanism. Spores are monolete, bilateral, bean-shaped, with a finely granulate perispore, measuring approximately 30–40 µm in length. Under humid forest-floor conditions, spores germinate within 2–4 weeks to produce a heart-shaped prothallus (gametophyte), which then requires a film of water for the biflagellate spermatozoids to swim from antheridia to archegonia for fertilisation. The resulting embryonic sporophyte takes several months to establish. However, this entire sexual pathway is largely superfluous in ecological terms, because the bulbils provide a far more efficient, reliable, and rapid means of local reproduction. Each bulbil is a pre-formed sporophyte that skips the vulnerable gametophyte stage entirely, roots within days of substrate contact, and grows to independence in weeks rather than months. In practice, A. bulbiferum relies overwhelmingly on vegetative propagation through bulbils for population maintenance and local spread, while the spore pathway may serve primarily for longer-distance dispersal — colonising new sites where wind-carried spores can reach but detached bulbils cannot.

Comparison with Similar Species

Asplenium bulbiferum occupies a unique morphological position within Asplenium, and comparisons with its relatives highlight just how anomalous this species is within the genus. Against A. nidus (bird’s nest fern): the differences could scarcely be more extreme. A. nidus has simple, entire, undivided, glossy, strap-shaped fronds 30–150 cm long forming a tight upright funnel rosette; A. bulbiferum has bipinnate-tripinnate, finely divided, lace-like fronds in a loose arching shuttlecock. A. nidus produces no bulbils and cannot be divided; A. bulbiferum produces abundant foliar bulbils and propagates itself effortlessly. A. nidus is tropical (zones 10–12, minimum 10°C); A. bulbiferum is cool-temperate (zones 9–11, tolerates brief frost). They are genetically close enough to share a genus but look nothing alike. Against A. antiquum (Japanese bird’s nest fern) and A. australasicum (crow’s nest fern): same story — simple entire fronds, rosette habit, no bulbils, tropical to warm-temperate. Against A. daucifolium (Mauritius spleenwort): this is the closest ecological and morphological analogue. A. daucifolium is also viviparous, producing foliar bulbils on bipinnate-tripinnate fronds, and was long confused with A. bulbiferum in cultivation. The key differences are geographic origin (A. daucifolium is endemic to the Mascarene Islands — Mauritius and Réunion — in the Indian Ocean), warmer growing requirements (tropical, minimum 10–12°C), and slightly coarser frond dissection with wider pinnule segments. Against A. gracillimum (hen and chickens fern, New Zealand): this species was formerly classified as a subspecies of A. bulbiferum but DNA evidence showed it to be an allooctoploid hybrid (2n = 288) between A. bulbiferum and A. hookerianum. It produces fewer bulbils, has larger spores, narrower scales with thread-like points, and often finer frond dissection. The two grow sympatrically in New Zealand and their ranges overlap, but they are reproductively isolated by ploidy difference. Against Woodwardia radicans (European chain fern): this unrelated fern (family Blechnaceae) produces bulbils at the tips of its massive fronds (up to 250 cm long) in a convergent example of foliar vivipary. However, it produces only one bulbil per frond tip (versus dozens across the frond surface in A. bulbiferum), its fronds are pinnate (not bi-tripinnate), and it is a much larger, coarser plant suited to woodland garden conditions in zones 8–10. Against Asplenium × lucrosum: this sterile hybrid (A. bulbiferum × A. dimorphum) is the plant most commonly sold as A. bulbiferum in the international nursery trade. It produces bulbils but its spores are malformed, its fronds are dimorphic (fertile and sterile fronds differ in segment width), and it cannot reproduce sexually — a commercially successful but biologically dead-end hybrid.

Reproduction & Propagation

Asplenium bulbiferum is, without exaggeration, the easiest fern in cultivation to propagate, and it achieves this distinction by eliminating every difficult step in the fern reproductive cycle. Where Adiantum requires meticulous spore culture, Platycerium demands keiki-like pup separation from a mounted specimen, and Nephrolepis needs stolon division, the mother fern hands you a ready-made baby plant, pre-rooted and pre-leafed, growing on the surface of its own fronds. The primary propagation method is bulbil harvest. Wait until the plantlets on the frond surface have developed 3–4 small fronds of their own and show visible root initials (white nubs at the base), typically at a size of 3–5 cm. Using clean scissors or a sharp blade, cut the plantlet free from the mother frond along with a small piece of the pinna to which it is attached — this attached tissue provides a nutrient bridge during the first days of establishment. Press the base of the plantlet firmly onto the surface of a small pot (7–9 cm) filled with damp, humus-rich compost mixed with perlite, burying only the root initials 3–5 mm deep. Do not bury the tiny fronds. Cover the pot with a clear plastic bag or place in a propagator at 15–20°C with high humidity (70–90% RH). Roots establish within 5–10 days, and new fronds appear within 2–4 weeks. Once active growth is visible, gradually reduce humidity cover over 7 days to harden the plantlet. The second method is even simpler: rather than cutting bulbils free, position a nursery tray of moist compost directly beneath the arching, bulbil-laden frond. Pin the frond gently to the compost surface using a bent wire or small stone so that the bulbils make contact with the substrate. The plantlets root in situ over 2–3 weeks, after which the connecting frond tissue can be severed and the tray of rooted babies pricked out into individual pots. A single mature frond can produce 5–15 viable plantlets in one season. The third method — spore propagation — is technically viable but practically pointless for this species. Spores germinate on sterile damp peat at 18–22°C in 3–6 weeks, prothalli develop over 2–3 months, and sporophytes appear 4–6 months after sowing. The entire process takes 8–14 months to produce a small plant — a plantlet that could have been obtained from a bulbil in one week. Spore culture is only justified for genetic diversity (bulbils are clones) or if no bulbil-producing parent plant is available. Division of the rhizome is possible for large, multi-crowned specimens: unpot, wash the roots, and separate crowns with a clean blade ensuring each division has at least 3–4 fronds and a healthy root mass. Pot divisions into fresh compost, maintain high humidity for 2 weeks, and resume normal care.

Cultivation & Substrate

Asplenium bulbiferum is a cool-growing fern that performs best in conditions replicating the moist, shaded understorey of New Zealand’s temperate forests — a climate profile quite different from the tropical warmth required by its bird’s-nest relatives. The ideal temperature range is 15–22°C, with winter minima no lower than 5°C and summer maxima no higher than 28°C. In warm climates (USDA zones 10–11), grow it in the coolest, most shaded position available: a south-facing wall (in the southern hemisphere, north-facing), the base of a shaded fence, or under a dense tree canopy. In cooler climates (zones 8b–9), it can be grown outdoors year-round in a sheltered, frost-free position with winter protection from heavy freeze events. As a container plant, use a mix of 2 parts peat-free multipurpose compost (or coco coir), 1 part fine bark, and 1 part perlite — the goal is a humus-rich, moisture-retentive but well-aerated substrate that mimics the decomposing leaf litter of the forest floor. Target pH is 5.5–6.5 (mildly acidic). Pot in a container one size larger than the root ball with drainage holes; overpotting leads to stagnant wet zones that invite root rot. Water regularly to maintain even moisture — the substrate should feel damp but not sodden at 2–3 cm depth. Unlike the crown-rotting risk in A. nidus, there is no tight rosette to trap water, so overhead watering and misting are both safe. Humidity of 50–70% is ideal; below 40%, pinnae tips brown. Grouping with other ferns, using a pebble tray, or running a humidifier during winter heating season all help. Feed with a balanced liquid fertiliser (half-strength 10-10-10 or 20-20-20) monthly from spring through early autumn; do not feed in winter. The plant responds well to an annual top-dressing of composted bark or leaf mould in spring, which mimics the natural addition of forest-floor litter. Repot every 2–3 years, or when the root ball fills the container. In a cool greenhouse or conservatory maintained at 8–18°C through winter, A. bulbiferum is one of the most reliable and rewarding ferns available, producing arching fronds laden with babies that can be shared indefinitely.

Common Mistakes to Avoid

The first and most persistent mistake growers make with Asplenium bulbiferum is expecting it to look like its famous relative A. nidus, the bird’s nest fern. They are in the same genus but share almost no visual features: A. nidus has simple, entire, glossy, strap-shaped fronds in a tight upright rosette; A. bulbiferum has finely divided, bipinnate-tripinnate, dark green, arching fronds in a loose shuttlecock habit. Buyers who order ‘an Asplenium’ are sometimes confused when the plant they receive looks more like a maidenhair on steroids than a bird’s nest. The second major error is growing it too warm. This is a cool-temperate New Zealand species, not a tropical fern. Sustained temperatures above 28°C cause frond yellowing, reduced bulbil production, and increased susceptibility to spider mites. Central heating in winter, radiator proximity, and placement near south- or west-facing windows in summer are all common culprits. If frond edges are crisping and turning brown in midsummer, heat stress is the likely cause before humidity is even considered. The third mistake is letting the bulbil-laden fronds trail onto the ground unchecked. The weight of developing plantlets naturally arches the fronds downward, and if the tips contact moist substrate, the babies root in situ, tethering the frond to the pot rim or the ground and creating a tangled mess. Either harvest plantlets when they reach 3–5 cm (3–4 fronds each) by snipping them free, or allow the frond to arch onto a prepared nursery tray positioned beneath it for intentional propagation. The fourth error is overwatering in winter combined with poor drainage. Although A. bulbiferum likes consistent moisture, it is less tolerant of waterlogged roots than its tropical relatives because its root system is adapted to well-aerated forest humus, not boggy conditions. In cool winter temperatures with reduced light and minimal growth, water uptake drops sharply, and saturated substrate leads to Pythium root rot detectable by a sour smell and blackened root tips. Reduce watering frequency in winter to once every 7–10 days and ensure the mix drains freely. The fifth is excessive direct sunlight: even 1–2 hours of unfiltered midday sun will bleach and scorch the delicate pinnae, which are thinner and more photosensitive than the leathery blades of A. nidus.

Seasonal Considerations

Asplenium bulbiferum is evergreen and does not enter true dormancy, but it follows a clear seasonal growth rhythm driven by photoperiod and temperature, and matching care intensity to this cycle produces the healthiest plants with the most abundant bulbil production. In spring (September–November in New Zealand, March–May in northern hemisphere cultivation), lengthening days and warming temperatures trigger a flush of new croziers from the rhizome crown. This is the time to resume monthly half-strength liquid feeding, increase watering frequency as new fronds expand, and repot if the root ball has filled its container. Spring is also the peak season for bulbil development on existing mature fronds — the previous year’s fronds begin producing plantlets in earnest as metabolic activity rises. In summer, maintain consistent moisture and protect from heat: if temperatures regularly exceed 25°C, move the plant to the coolest available position, increase air circulation, and mist the surrounding air (not the fronds directly) to boost humidity through evaporative cooling. Outdoor plants in sheltered gardens should be in full shade during summer. This is the main growth period — fronds elongate, arch outward, and the heaviest crop of bulbils develops. In autumn, reduce feeding to every 6 weeks, then cease entirely by late autumn. Stretch watering intervals as temperature and light drop. Harvest any remaining ripe bulbils (3–5 cm, with 3–4 fronds and visible root initials) before the slow-growth winter phase, as plantlets established in autumn will develop root systems before cold weather arrives. In winter, the plant rests but remains green. Water only when the top 2–3 cm of substrate feels dry — typically every 7–12 days in a cool room. Do not fertilise. A cool winter rest at 8–15°C is actively beneficial: it replicates the plant’s natural New Zealand winter and promotes vigorous spring growth and heavy bulbil production the following season. Plants kept constantly warm (above 20°C year-round) often produce fewer bulbils and more leggy, pale fronds than those given a genuine cool period. Remove any fully browned older fronds by cutting cleanly at the base of the stipe.

Diseases & Pests

Asplenium bulbiferum has no serious insect or disease problems under good culture, and its cool-growing preference actually protects it from several pests that plague tropical ferns. However, it is not immune. Scale insects — particularly fern scale (Pinnaspis aspidistrae) and brown soft scale (Coccus hesperidum) — are the most frequent arthropod pest, appearing as small limpet-like crusts 1–2 mm long on the stipes (stem-like frond bases) and along the rachis where they tap into phloem tissue. Infestations produce honeydew that supports sooty mould growth on pinnae surfaces, reducing photosynthesis. Treat light infestations by physical removal with a cotton swab dipped in 70% isopropyl alcohol; for heavier attacks, apply neem oil or horticultural mineral oil at 1–2% concentration to all frond surfaces, repeating at 10-day intervals for three applications to catch emerging crawlers. Slugs and snails are significant pests on outdoor and greenhouse-grown plants, particularly in the humid, shaded conditions that A. bulbiferum prefers. They rasp irregular holes in the soft pinnae and can destroy emerging croziers overnight. Use iron-phosphate-based slug pellets (non-toxic to wildlife) around the base of the plant, or hand-pick after dark with a torch. Copper tape around pot rims provides a non-chemical barrier for container specimens. Mealybugs (Pseudococcus species) occasionally colonise the frond bases near the rhizome crown, especially in greenhouse culture where warm microclimates develop near heating pipes. Inspect regularly by gently parting the frond bases and remove colonies with alcohol-soaked cotton buds. Spider mites (Tetranychus urticae) appear primarily when plants are kept too warm and dry — conditions that contradict the species’ requirements. Fine stippling on pinnae upper surfaces and wispy webbing between segments are diagnostic. Increase humidity and reduce temperature; apply insecticidal soap if the infestation is established. Fungal leaf spot (Colletotrichum and Cercospora species) produces discrete circular brown spots 2–8 mm across on pinnae, typically in conditions of high humidity with poor air circulation and stagnant air. Remove affected fronds, improve ventilation, and avoid wetting foliage in the evening. Pythium root rot is the most destructive disease, caused by waterlogged substrate in cool conditions when the root system is relatively inactive; detectable by a sour compost smell and blackening roots. Unpot, trim all dead roots, dust with cinnamon or sulphur, and repot into fresh free-draining mix.

Indoor Growing & Terrariums

Asplenium bulbiferum makes an excellent and forgiving indoor fern, but it has one requirement that sets it apart from the tropical species that dominate the houseplant market: it prefers cool rooms. The ideal indoor temperature range is 15–22°C, which makes it better suited to unheated spare bedrooms, cool hallways, north-facing conservatories, and sheltered porches than to centrally heated living rooms where temperatures routinely exceed 22–24°C in winter. Position the plant at an east-facing or north-facing window (in the northern hemisphere) where it receives bright indirect light without direct sun. South- or west-facing windows work only if the plant is set 1.5–2 m back from the glass or behind a sheer curtain. Measured at the plant, target 1500–3000 lux; the fern will tolerate lower light (down to 800 lux) but will produce fewer fronds and fewer bulbils, losing much of its ornamental interest. Bathrooms with a window are often excellent locations: the daily humidity spikes from showers replicate forest-floor moisture, and bathrooms tend to be cooler than main living spaces. Kitchens work similarly, provided the plant is kept away from cooker heat. The single biggest indoor care advantage of A. bulbiferum over A. nidus is the absence of a crown-rotting rosette — there is no tight funnel of frond bases to trap water. You can water overhead, mist freely, and even shower the plant monthly to wash dust from the finely divided pinnae without risk. This relaxed watering tolerance makes it significantly more forgiving than the bird’s nest ferns for casual growers. Humidity should be maintained above 50% during winter when central heating dries indoor air. A pebble tray filled with water, grouping with other plants, or a small ultrasonic humidifier all help. The cascading, fountain-like silhouette of a mature specimen with arching, bulbil-laden fronds is particularly effective on a shelf, plant stand, or in a hanging basket where the fronds can arch downward naturally. The bulbils themselves become a social currency: visitors invariably notice the tiny baby plants growing on the fronds, and detaching a few to give as gifts is one of the great pleasures of growing this species. Keep the plant away from heating vents, radiators, and air-conditioning outlets, all of which create dry air currents that brown pinnae tips within days. A. bulbiferum is not listed as toxic by the ASPCA and is considered safe for households with cats and dogs.

Terrarium Setup

Asplenium bulbiferum is a strong candidate for cool terrariums and enclosed glass gardens, with one significant advantage over most terrarium ferns: the bulbils provide a self-renewing source of new plants within the enclosure, creating a dynamic, self-propagating ecosystem without any intervention. In a sealed or semi-sealed glass terrarium of 40–60 cm height, the fern benefits from the constant high humidity (70–95% RH) that is difficult to maintain in open-air culture, and the enclosed environment buffers temperature fluctuations that can stress this cool-growing species. Use a 3–4 cm drainage layer of LECA or fine volcanic gravel at the base, a thin mesh separator, then 6–8 cm of a mix of fine bark, sphagnum moss, and perlite (1:1:1), or a humus-rich compost blended with perlite for aeration. Position the mother fern off-centre or toward the back, leaving space for the arching fronds to cascade without pressing against the glass. As bulbils develop and drop onto the substrate surface, they will root spontaneously in the humid terrarium environment, eventually producing a colony of small ferns around the base of the parent plant. This natural spreading behaviour is part of the species’ charm in an enclosed setup, but it does require periodic thinning: remove excess plantlets every 3–6 months to prevent overcrowding that blocks light to the parent and companion plants. Companion planting works beautifully: Selaginella kraussiana as groundcover, miniature Hymenophyllum (filmy ferns) on cork bark pieces, Pilea species for textural contrast, and sheet mosses (Hypnum, Vesicularia) on rocks and substrate. The critical caveat is temperature: A. bulbiferum is a cool-growing fern that dislikes sustained warmth above 25°C. A sealed terrarium placed in direct sunlight or under powerful grow lights will overheat rapidly, cooking the fern within hours. Position under moderate indirect light or a low-wattage LED grow light at 2000–3000 lux, well away from windows that receive direct sun. Cool-temperate rooms (15–20°C) are ideal, and an unheated room that drops to 8–12°C in winter is perfectly acceptable — the fern will grow more slowly. This cool-tolerance is actually an advantage over tropical terrarium ferns like Nephrolepis, which sulk below 18°C.

Landscape & Garden Use

Asplenium bulbiferum can be used in the garden wherever its hardiness and habitat preferences are matched. Ferns are classic choices for shaded borders, woodland gardens, stumperies, rockeries, stream-side plantings, and ground-cover under trees.

Landscape Tips

• Companions: Hostas, Astilbe, Heuchera, Tiarella, Epimedium, hellebores, snowdrops and other shade-tolerant perennials are classic partners.
• Soil preparation: Incorporate leaf mould or composted bark to improve moisture retention and mimic a forest floor.
• Mulching: A 3–5 cm mulch of chipped bark or leaf litter protects the rhizomes, conserves moisture, and slowly releases nutrients.
• Watering: Establish new plantings with regular deep watering during the first growing season; most hardy ferns need only occasional supplemental irrigation once established.

Conservation & Collector Notes

In New Zealand, Asplenium bulbiferum is classified as ‘Not Threatened’ by the New Zealand Threat Classification System (Department of Conservation), reflecting its wide distribution across both main islands, Stewart Island, and the Chatham Islands, and its abundance in remaining native forest. It is one of the commonest ground ferns encountered in lowland to lower montane bush throughout the North Island and in suitable habitats in the South Island, and its prolific vegetative reproduction via bulbils ensures rapid local population recovery after disturbance. The species colonises regenerating bush, forest margins, and even shaded garden escapes, demonstrating considerable ecological resilience. However, the broader context is less comfortable. New Zealand has lost approximately 70% of its original lowland forest cover since Polynesian and European settlement, and while A. bulbiferum persists in remaining fragments, its historical abundance would have been far greater. In the South Island, the species has a more restricted distribution than in the North Island, being largely confined to Marlborough Sounds, northwest Nelson, the west coast, Fiordland, and scattered southern coastal sites, with notable absence from the Canterbury Plains and much of the eastern rain-shadow region. Browsing by introduced mammals — particularly deer (Cervus species), possums (Trichosurus vulpecula), and goats (Capra hircus) — reduces fern understorey density in heavily invaded forests, and A. bulbiferum fronds are palatable to these herbivores. Fenced mainland island sanctuaries and offshore predator-free islands (Ulva Island, Tiritiri Matangi) show dramatically denser fern understorey including A. bulbiferum than unfenced mainland forests, confirming the suppressive effect of introduced browsers. In Australia, where the species has been reported from scattered localities in Victoria and New South Wales, populations are sparse and some records may represent allied taxa rather than true A. bulbiferum; the taxonomic status of Australian material requires further molecular work. The species is not listed on the IUCN Red List and is not subject to any CITES trade restrictions. Its prolific vegetative reproduction, broad habitat tolerance within forested landscapes, and abundance in cultivation (albeit often as the hybrid A. × lucrosum) mean that it faces no foreseeable extinction risk, though continued deforestation and invasive herbivore pressure remain ongoing concerns for wild New Zealand populations.

Collector Notes

The collector’s primary challenge with Asplenium bulbiferum is ensuring that the plant in hand is actually the true species and not the ubiquitous sterile hybrid Asplenium × lucrosum (A. bulbiferum × A. dimorphum), which has dominated international nursery production for decades. This hybrid, formally described by Perrie, Shepherd, and Brownsey in 2005, arose from a chance cross between A. bulbiferum (endemic to New Zealand) and A. dimorphum (endemic to Norfolk Island) in cultivation — the two species never meet in the wild. The hybrid inherited bulbil production from A. bulbiferum, making it superficially identical to the true species, but it can be distinguished by three characters: (1) dimorphic fronds, where fertile fronds bearing sori have noticeably narrower pinnule segments than sterile fronds on the same plant — true A. bulbiferum shows little dimorphism; (2) non-viable spores, which are malformed and shrivelled rather than plump and uniform when examined under a hand lens; (3) a generally more robust, coarser habit than the true species. The name lucrosum means ‘profitable’ in Latin, a wry acknowledgement of how commercially successful this mislabelled hybrid has been. To obtain guaranteed true A. bulbiferum, source from New Zealand specialist native-plant nurseries (e.g., Fronds NZ, Oratia Native Plant Nursery) or collect bulbils from verified wild-sourced plants. A further taxonomic confusion involves Asplenium gracillimum, which was formerly treated as a subspecies of A. bulbiferum but is now recognised as a distinct species — an allooctoploid (2n = 288) resulting from hybridisation between tetraploid A. bulbiferum and A. hookerianum. A. gracillimum has larger spores, fewer bulbils, narrower scales with fine thread-like points (versus the broader, ovate scales of A. bulbiferum), and generally finer frond dissection. In New Zealand, both species occur sympatrically in some forests, and hybrids between them (hexaploid, sterile) are known. For the collector interested in viviparous ferns as a group, A. bulbiferum should be grown alongside A. daucifolium (Mauritius spleenwort, also viviparous, from the Mascarene Islands — warmer-growing), Woodwardia radicans (European chain fern, produces bulbils at frond tips — hardy to zone 8), and Woodwardia unigemmata (produces 1–3 bulbils per frond — cold-hardy). Together these form a compelling display of convergent evolution in vegetative fern reproduction.

Ethnobotany & Cultural Significance

Asplenium bulbiferum holds a significant place in Māori culture as one of several native fern species whose young unfurling fronds (croziers or fiddleheads) are harvested as a traditional food, known collectively as pikopiko. The species is called by several Māori names — pikopiko, mouku, and mauku — depending on regional dialect, with mauku being the most widely used in ethnobotanical literature. The edible part is the young, tightly coiled crozier and the first 10–15 cm of the expanding frond, harvested before the blade unfurls and the tissues lignify. The raw crozier has a crisp texture and a mild, slightly sweet flavour often compared to asparagus or green beans, earning it the colonial nickname ‘bush asparagus.’ Preparation methods include peeling and washing to remove any residual bitterness, followed by steaming, boiling, stir-frying, or eating raw in salads. Modern New Zealand chefs have incorporated pikopiko into fine-dining menus as a showcase of indigenous kai (food), using it as a garnish, blending it into pestos and spreads, chopping it into bread doughs, and pairing it with seafood. Nutritional analyses of raw croziers show moderate protein (2–3 g per 100 g fresh weight), notable iron and calcium content, and high vitamin A and C levels. Beyond food, A. bulbiferum had medicinal and ritual significance. An infusion of the roots was used as a wash for cutaneous complaints (skin diseases), and a root-derived wash was applied to treat sore eyes — applications documented in multiple early ethnobotanical surveys of Māori plant use. In ritual practice, when felling trees for waka (canoes), bark and mauku were placed on a fire kindled at the base of the tree before the appropriate karakia (incantation) was recited and the tree was felled — suggesting the fern held symbolic or spiritual value in the process of taking a tree from the forest. The genus name Asplenium itself encodes a European ethnobotanical claim: from the Greek a-splen (without spleen), reflecting the Dioscoridean doctrine of signatures under which the elongate sori of spleenwort ferns were thought to resemble the human spleen and were therefore prescribed for spleen disorders. This belief persisted in European herbals from Dioscorides (ca. 70 CE) through Gerard (1597) and Culpeper (1653), though no pharmacological basis has ever been established for any spleenwort species.

Frequently Asked Questions