Adiantum hispidulum Sw., Pteridaceae

Click on an image for links to BIGGER PICTURES

Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk; score: 18 (Hawaii-Pacific Weed Risk Assessment for Adiantum hispidulum)

Other Latin names:  (no species-level synonyms found)

Common name(s): [more details]

English: five-finger jack, rosy maidenhair fern, rough maidenhair fern

Habit:  fern

Description:  "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)." (CABI datasheet; includes links to references)

(see also description in A Tropical Garden Flora, p. 49)

Habitat/ecology:  ". . . [Adiantum hispidulum] is one of the few Adiantum species that does well in both sun and shade." (A Tropical Garden Flora, p. 49)

On Vava'u (Tonga): "on mossy limestone rocks, moist shady bank near lagoon" (Plants of Tonga, p. 36)

"In Hawaii it [Adiantum hispidulum] 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)." (CABI datasheet)

"This a hardy fern which performs best in soils containing appreciable organic matter with plenty of moisture. It will, however, tolerate a surprising amount of dryness." (ANSPA)

In cultivation: "Grow in organically rich, fertile, consistently moist, well-drained soils in part shade to full shade. Best in bright but sun-dappled or filtered light in sheltered locations with good air circulation. Part shade is better than full shade. Container plants grown as houseplants should be placed near sunny windows but not in direct sun. Foliage may scorch in full sun but growth will lose vigor in too much shade. Water freely and evenly, but avoid overwatering. Soils should never be allowed to dry out. Mist foliage to increase humidity. Best indoor daytime temperatures are around 70 degrees F., dipping to 60 degrees F. at night." (MoBot)

Propagation:  "Propagation is usually carried out by division of the rhizome. Propagation can also be carried out from spores. . . ." (ANSPA)

"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. . . .

"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." (CABI datasheet)

RE: cultivation in Hawaii: "Once established, [Adiantum hispidulum] propgates itself readily, spreading freely and at times becoming an unwelcome problem plant." (A Tropical Garden Flora, p. 49)

Native range:  "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)." (CABI datasheet)

Impacts and invaded habitats:  "A[diantum] 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." (CABI datasheet)

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Cook Islands Southern Cook Islands	Rarotonga Island		Consortium of Pacific Herbaria (2018)
Federated States of Micronesia Pohnpei Islands	Pohnpei Island		Consortium of Pacific Herbaria (2018)
Fiji Fiji Islands	Vanua Levu Island		Consortium of Pacific Herbaria (2018)
Fiji Fiji Islands	Viti Levu Island		Consortium of Pacific Herbaria (2018)
French Polynesia French Polynesia Islands	French Polynesia Islands		Consortium of Pacific Herbaria (2018)
French Polynesia Austral (Tubuai) Islands	Rurutu Island		Consortium of Pacific Herbaria (2018)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island		Consortium of Pacific Herbaria (2018)
State of Hawaii Hawaiian Islands	Hawaiian Islands		Consortium of Pacific Herbaria (2018)
State of Hawaii Hawaiian Islands	Kaua‘i Island		Consortium of Pacific Herbaria (2018)
State of Hawaii Hawaiian Islands	Lāna‘i Island		Consortium of Pacific Herbaria (2018)
State of Hawaii Hawaiian Islands	Maui Island		Consortium of Pacific Herbaria (2018)
State of Hawaii Hawaiian Islands	O‘ahu Island		Consortium of Pacific Herbaria (2018)
New Caledonia New Caledonia Archipelago	New Caledonia (island)		Consortium of Pacific Herbaria (2018)
Pacific Pacific	Pacific islands		Taranaki Educational Resource Research Analysis and Information Network (year unknown) accessed 20180409
Pacific Pacific	Polynesia		Taranaki Educational Resource Research Analysis and Information Network (year unknown) accessed 20180409
Pacific Pacific	Polynesia	native	Missouri Botanical Garden (year unknown) accessed 20180409
Palau Palau (Belau ) (main island group)	Ngeruktabel		Consortium of Pacific Herbaria (2018)
Palau Palau (Belau ) (main island group)	Palau Islands (main island group)		Consortium of Pacific Herbaria (2018)
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)		Consortium of Pacific Herbaria (2018)
Pitcairn Islands Pitcairn Islands	Pitcairn Islands		Consortium of Pacific Herbaria (2018)
Tonga Tonga Islands	Tonga Islands		Yuncker, T. G. (1959) (p. 36) In Tonga: "Occasional"
Tonga Tonga Islands	Tonga Islands		Consortium of Pacific Herbaria (2018)
Tonga Tongatapu Group	Tongatapu Island		Yuncker, T. G. (1959) (p. 36) Source: Nelson; ref doesn't say whether native or not
Tonga Vava‘u Group	Vava‘u Island		Yuncker, T. G. (1959) (p. 36) Voucher cited: Yuncker 16196; ref doesn't say whether native or not
Vanuatu New Hebrides Islands	Êfaté (Efete) Island		Consortium of Pacific Herbaria (2018)
Vanuatu New Hebrides Islands	Erromango Island		Consortium of Pacific Herbaria (2018)
Vanuatu New Hebrides Islands	Malakula (Malekula) Island		Consortium of Pacific Herbaria (2018)
Vanuatu New Hebrides Islands	Tanna Island		Consortium of Pacific Herbaria (2018)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Asia Asia (Pacific rim)	Malesia		Taranaki Educational Resource Research Analysis and Information Network (year unknown) accessed 20180409
Australia Australia	Australia		Taranaki Educational Resource Research Analysis and Information Network (year unknown) accessed 20180409
Australia Australia	Australia	native	Missouri Botanical Garden (year unknown) accessed 20180409
Australia Australia (continental)	New South Wales	cultivated	Australian Native Plants Society (Australia) (year unknown) accessed 20180409, probable implication is that it's native, but not explicitly stated in ref
Australia Australia (continental)	Australia (continental)	cultivated	Australian Native Plants Society (Australia) (year unknown) Northern Territory, accessed 20180409, probable implication is that it's native, but not explicitly stated in ref
Australia Australia (continental)	Queensland		Consortium of Pacific Herbaria (2018)
Australia Australia (continental)	Queensland	cultivated	Australian Native Plants Society (Australia) (year unknown) accessed 20180409, probable implication is that it's native, but not explicitly stated in ref
Australia Australia (continental)	Victoria (Australia)	cultivated	Australian Native Plants Society (Australia) (year unknown) accessed 20180409, probable implication is that it's native, but not explicitly stated in ref
Malaysia Malaysia	Malaysia (country of)	native	Missouri Botanical Garden (year unknown) accessed 20180409
New Zealand New Zealand	Bay of Islands		Consortium of Pacific Herbaria (2018)
New Zealand New Zealand	New Zealand (country)		Taranaki Educational Resource Research Analysis and Information Network (year unknown) accessed 20180409
New Zealand New Zealand	New Zealand (country)	native	Missouri Botanical Garden (year unknown) accessed 20180409
United States (west coast) United States (west coast states)	USA (California)		Consortium of Pacific Herbaria (2018)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Africa Africa	Africa		Taranaki Educational Resource Research Analysis and Information Network (year unknown) accessed 20180409
Africa Africa	Africa	native	Missouri Botanical Garden (year unknown) accessed 20180409
Africa Africa	Madagascar		Consortium of Pacific Herbaria (2018)
India India	India (southern)	native	Missouri Botanical Garden (year unknown) accessed 20180409
United States of America United States	United States	native	Missouri Botanical Garden (year unknown) accessed 20180409

Comments:  In Hawaii: "[Adiantum hispidulum] is easily cultivated as a ground cover or in containers and is one of the few Adiantum species that does well in both sun and shade. Once established, it propagates itself readily, spreading freela and at times becoming an unwelcome problem plant." [emphasis: PIER] (A Tropical Garden Flora, p. 49)

Control:  "Prevention: 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.

"Control: 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." (CABI datasheet)