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21 December 2013

Adiantum hispidulum (rosy maidenhair fern)

Datasheet Type: Invasive species


This datasheet on Adiantum hispidulum covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Impacts, Uses, Prevention/Control, Further Information.


Preferred Scientific Name
Adiantum hispidulum Sw.
Preferred Common Name
rosy maidenhair fern
International Common Names
rough maidenhair fern
Local Common Names
five-fingered Jack
New Zealand
rosy maidenhair
EPPO code
ADIHI (Adiantum hispidulum)


Adiantum hispidulum (rosy or rough maidenhair fern); habit. Kula Botanical Garden, Maui, Hawaii, USA. March, 2011.
Habit, showing fronds
Adiantum hispidulum (rosy or rough maidenhair fern); habit. Kula Botanical Garden, Maui, Hawaii, USA. March, 2011.
©Forest & Kim Starr-2011 - CC BY 3.0
Adiantum hispidulum (rosy or rough maidenhair fern); habit. Pohakuokala Gulch, Maui, Hawaii, USA. August, 2005.
Adiantum hispidulum (rosy or rough maidenhair fern); habit. Pohakuokala Gulch, Maui, Hawaii, USA. August, 2005.
©Forest & Kim Starr-2005 - CC BY 3.0
Adiantum hispidulum (rosy or rough maidenhair fern); habit. Olinda, Maui, Hawaii, USA. November 15, 2009.
Adiantum hispidulum (rosy or rough maidenhair fern); habit. Olinda, Maui, Hawaii, USA. November 15, 2009.
©Forest & Kim Starr-2009 - CC BY 3.0

Summary of Invasiveness

A. hispidulum, the rosy maidenhair fern, is known to be invasive and weedy in the main Hawaiian Islands where it has escaped from cultivation. In Hawaii it is a serious weed generally of mesic slopes and gulch bottoms and is often abundant along intermittent and perennial streams. It is capable of invading intact plant communities and pristine areas. A. hispidulum usually begins to colonize in areas where there is some type of natural disturbance such as landslides, tree falls, disturbance by feral ungulates, or even a single dislodged rock. The dense clumps and rhizome mats of this fern prevent establishment of many native taxa including rare species. A. hispidulum can also overrun other ferns and herbs (Wilson, 1996; Palmer, 2003; H. Oppenheimer, Hawaii Plant Extinction Prevention Program (PEP), USA, personal communication, 2013). It is naturalized locally in a few other parts of the world including the southeastern USA and parts of its native range including eastern and southern Africa, Malaya, and Singapore.

Taxonomic Tree

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Plant Type



Terrestrial ferns, plants stiff, erect. Rhizomes erect to decumbent, short-creeping, with dark brown scales. Fronds clustered at apex of rhizome, erect, (6-)15–60 cm tall, young fronds rosy pink; stipes dark brown, rough, up to 30 cm long, clothed with short dark fibrils and hairs; blades ± fan-shaped, deltate to ovate, dichotomously branched at 45º angle into 7–15 branches; pinnules asymmetrically oblong-rectangular to diamond shaped, 0.5–1.7 cm long, 3–8 mm wide, the upper and outer margins gently rounded, finely toothed, the lower straight and entire, softly pubescent to ± glabrate, veins mostly ending in marginal teeth; pinnule stalks 0.5–1 mm long. Sori 6–14 per segment, small, closely placed on upper and outer edges in notches between the lobes; indusium flaps 3–4(–5) mm wide, circular to broadly oblong or kidney-shaped, covered with numerous small, pointed brown hairs (Verdcourt, 2002; Palmer, 2003).


A. hispidulum is widespread and presumed to be native from Australia and Africa to Asia, Malesia and various Pacific Islands (Palau, Fiji, New Caledonia, Vanuatu), and eastward to Polynesia (Austral Islands (Rapa), Society Islands (Tahiti), Cook Islands (Raratonga), and New Zealand. However, it is sporadic throughout its native range, and in addition to native plant communities it often occurs in disturbed habitats. For example around villages, along trails, on roadside banks, rock walls, or in the understory of forestry plantings, suggesting a potential for invasiveness. Australia is the type locality and presumably the centre of diversity for A. hispidulum, as it occurs in all States and Territories. Bostock et al. (1998) recognize four taxonomic varieties in Australia. The widespread var. hispidulum is terrestrial or lithophytic in a variety of habitats, including open forest and as relictual populations in gorges in arid areas. The other three varieties are said to be more localized and endemic to Australia. In this treatment, however, a single variable species is recognized without infraspecific taxa (subspecies, varieties, or forms), following International Plant Names Index (IPNI) (2013) and Tropicos (2013).

Distribution Map

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Distribution Table

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History of Introduction and Spread

A. hispidulum has become widely naturalized and weedy in Hawaii, where it grows in dry to mesic, sunny and rocky slopes, woods or trails on all of the main islands (not recorded from Niihau). Its date of introduction is unknown, but it was not recorded by Hillebrand (1888). It was first collected in the wild on Oahu in 1923 (Wilson, 1996).
In continental North America (USA) it is introduced and represented in the flora by sporadic escapes from cultivation and possibly naturalized locally (Paris, 1993) in Connecticut and Georgia. It is also reported from Florida and Louisiana, where it usually occurs on banks and old walls, 0-100 m elevation.
This species is sporadic throughout east tropical and temperate Africa. In East Africa it is confined to moist shaded habitats in South Africa (Cape Province, Natal, and Transvaal), Mozambique, Malawi, Kenya, Tanzania, and Ethiopia (Schelpe and Anthony, 1986). In Natal, it has been recorded at 830 m altitude where it may have escaped from cultivation, and it has also been found naturalized in a few localities on the Cape Peninsula.
It is uncommon in Malaya and not seen in the wild, or in primary forests, but only near villages (Holttum, 1954). In Java it is found throughout, usually in the lower hilly regions, on steep earth banks in shady places. In Singapore it is presumably native and occurs on bare but shaded earth banks around the suburbs of the city but it is not common (Holttum, 1954).

Risk of Introduction

A. hispidulum is sporadic throughout its native range, but is known to escape from cultivation via spores. A. hispidulum may colonize native plant communities as well as disturbed habitats such as around villages, along trails, on roadside banks, rock walls, or in the understory of forestry plantings. This species is potentially invasive in tropical and subtropical moist to wet environments and most likely spreads from cultivated plants by spore dispersal.

Means of Movement and Dispersal

Spores of A. hispidulum and other fern species are transported and dispersed primarily by air currents and wind. Spores may be transported in the soil on shoes or stuck to fur of animals but this method of spore dispersal is unlikely. The spores require a moist, shady, stable environment to germinate and grow into gameophytes and eventually into sporophytes or the spore producing phase. Many species of Adiantum, including A. hispidulum, are grown horticulturally and may spread unintentionally from cultivated plants.

Pathway Causes

Pathway causeNotesLong distanceLocalReferences
Disturbance (pathway cause)In Singapore, A. hispidulum occurs on bare but shaded earth banks around the suburbs of towns. Yes
Escape from confinement or garden escape (pathway cause)Escaped from cultivation and/or naturalized in south eastern USA, Hawaii, Natal and Singapore Yes

Pathway Vectors

Pathway vectorNotesLong distanceLocalReferences
Wind (pathway vector) YesYes 

Similarities to Other Species/Conditions

A. hispidulum may be distinguished from related maidenhair species (e.g. A. capillus-veneris, A. aethiopicum, A. raddianum) by it fronds that repeatedly fork at 45º angles, stipes clothed with short, dark fibrils and hairs, and pinnules with short, light brown hairs.


A. hispidulum occurs in dry to mesic, sunny to shady, usually moist rocky slopes, cliffs, woods, gulch bottoms, trails, roadside banks, rock walls, and understory of forestry plantings and native forest.

Habitat List

CategorySub categoryHabitatPresenceStatus
TerrestrialTerrestrial – ManagedManaged forests, plantations and orchardsPresent, no further details 
TerrestrialTerrestrial – ManagedRail / roadsidesPresent, no further details 
TerrestrialTerrestrial ‑ Natural / Semi-naturalNatural forestsPresent, no further details 
TerrestrialTerrestrial ‑ Natural / Semi-naturalRocky areas / lava flowsPresent, no further details 

Biology and Ecology


Based on chromosome counts of material from Australia and Ceylon, A. hispidulum is an apogamous hexaploid (has six sets of chromosomes), with a chromosome number of n = ca. 170-180 (Manton and Sledge, 1954). The base chromosome number in A. hispidulum appears to be 29 rather than 30, the usual base number for the genus (Brownlie, 1977).

Reproductive Biology

The apogamous (asexual) life cycle of certain ferns means that they produce 32, larger than normal diploid spores per sporangium, instead of the normal 64 haploid spores (Moran, 2004). Other apogamous taxa with higher polyploid chromosome numbers (triploid, tetraploid, hexaploid, etc.) cannot reproduce sexually either. When their spores germinate the resulting prothallus (gametophyte or gamete producing phase in a fern’s life cycle) does not produce sex organs but proliferates vegetatively without fertilization. The resulting sporophyte (spore producing) plantlet grows to maturity and in turn produces fronds with apogamous spores. Apogamous reproduction is advantageous in ferns that grow in dry habitats for two reasons: firstly apogamous ferns lack swimming sperm and there is no need for water in reproduction; and secondly their prothallus matures faster than those of sexually reproducing ferns (Moran, 2004). Apogamous ferns generally have wider geographic distributions than their sexually reproducing relatives. This appears to be the case for A. hispidulum, thus explaining its wide distribution, success in colonizing dry to mesic, disturbed habitats, and invasive tendencies.

Physiology and Phenology

Apogamy may explain the wide distribution, success in colonizing dry to mesic, disturbed habitats, and invasive tendencies of A. hispidulum. In addition to this the growth rate of all life stages of A. hispidulum is much greater than those of native fern species on Hawaiian islands.


Climate typeDescriptionPreferred or toleratedRemarks
Af - Tropical rainforest climate> 60mm precipitation per monthPreferred 
Am - Tropical monsoon climateTropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))Preferred 
As - Tropical savanna climate with dry summer< 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])Preferred 
Aw - Tropical wet and dry savanna climate< 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])Preferred 
Cf - Warm temperate climate, wet all yearWarm average temp. > 10°C, Cold average temp. > 0°C, wet all yearPreferred 

Latitude/Altitude Ranges

Latitude North (°N)Latitude South (°S)Altitude lower (m)Altitude upper (m)


ParameterLower limitUpper limitDescription
Dry season duration  number of consecutive months with <40 mm rainfall
Mean annual rainfall1800 mm; lower/upper limits

Soil Tolerances

Soil texture > medium
Soil reaction > acid
Soil reaction > neutral
Soil drainage > free

Impact Summary

Environment (generally)Negative

Impact: Environmental

Impact on Habitats

This species can cause habitat degradation by forming dense mats that outcompete or prevent the establishment and growth of native plants (Weller et al., 2010).

Impact on Biodiversity

The dense mats formed by this fern species can smother, exclude, or prevent establishment of native plant species, including at least five federally listed endangered species; Asplenium dielpallidum, Delissea kauaiensis, Euphorbia haeleeleana, Isodendrion laurifolium and Psychotria hobdyi (Weller et al., 2010). Other thretened and federally listed endangered species affected by A. hispidulum in Hawaii include Diellia erectaDiellia manniiCtenitis squamigera and Remya mauiensis (R. Aguraiuja, Tallin Botanical Garden, Estonia, personal communication, 2015).

Threatened Species

Threatened speciesWhere threatenedMechanismsReferencesNotes
Asplenium dielpallidum
Competition - monopolizing resources
Competition - shading
Competition - smothering
Rapid growth
Delissea kauaiensis
Competition - monopolizing resources
Competition - shading
Competition - smothering
Rapid growth
Euphorbia haeleeleana
Competition - monopolizing resources
Competition - shading
Competition - smothering
Rapid growth
Isodendrion laurifolium
Competition - monopolizing resources
Competition - shading
Competition - smothering
Rapid growth
Psychotria hobdyi (Hobdy's wild-coffee)
Competition - monopolizing resources
Competition - shading
Competition - smothering
Rapid growth
Poa mannii (Mann's bluegrass)
Competition - monopolizing resources
Pritchardia munroi (Kamalo pritchardia)
Competition - smothering
Remya mauiensis (Maui remya)
Schiedea apokremnos (Kauai schiedea)
Schiedea hookeri (sprawling schiedea)
Competition - monopolizing resources
Ecosystem change / habitat alteration

Risk and Impact Factors


Proved invasive outside its native range
Has a broad native range
Abundant in its native range
Highly adaptable to different environments
Is a habitat generalist
Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
Pioneering in disturbed areas
Tolerant of shade
Highly mobile locally
Benefits from human association (i.e. it is a human commensal)
Fast growing
Has high reproductive potential
Reproduces asexually

Impact outcomes

Damaged ecosystem services
Ecosystem change/ habitat alteration
Modification of successional patterns
Monoculture formation
Negatively impacts cultural/traditional practices
Reduced native biodiversity
Threat to/ loss of endangered species
Threat to/ loss of native species
Negatively impacts animal/plant collections

Impact mechanisms

Competition - monopolizing resources
Competition - shading
Competition - smothering
Competition (unspecified)
Interaction with other invasive species
Rapid growth

Likelihood of entry/control

Highly likely to be transported internationally accidentally
Highly likely to be transported internationally deliberately
Difficult to identify/detect as a commodity contaminant
Difficult/costly to control

Uses List

General > Botanical garden/zoo
Ornamental > Potted plant

Detection and Inspection

This species can be detected by visual identification, facilitated by using a reference book (Heath and Chinnock, 1974) or key (Palmer, 2003).

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.


The cultivation and sale of

A. hispidulum

in the horticultural trade should be discouraged and the public should be made aware of its invasive tendencies.  


Manual eradication of

A. hispidulum

is possible and probably the only effective control measure if conducted repeatedly in accordance with their  growth and regeneration cycles. Pulling up plants destabilizes the soil, and new plants may become established at the same sites by germination of spores remaining in the soil.   Control of

A. hispidulum

is extremely difficult due to transport of spores by air currents and wind over long distances. In addition to this, 

A. hispidulum

has high spore production, high germination and rapid growth rates.  
Monitoring and Surveillance

A. hispidulum

can be detected by visual identification and surveillance on the ground.   
Ecosystem restoration

A. hispidulum

must be manually removed and eradicated to allow ecosystem recovery.


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Published online: 21 December 2013





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