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Description: Known in English as the “false staghorn fern,” Dicranopteris linearis is a vigorously creeping plant that spreads outward laterally by extensive rhizomes to form large clumps (thus its occasional name in English as the “scrambling fern”). D. linearis is still referred by some botanists by it binomial synonym Gleichenia linearis. The rhizomes of D. linearis have tips covered with dense scale, and develop at or just beneath the soil surface where they intermittently send up fronds that are large, stiff and dichotomously branched. Stone (1970:51) provided a key description of the wiry stems of this savanna fern D. linearis: “Branches repeatedly forking, each fork with 2 basal, backward-directed, short fronds, and two forward-directed longer fronds; pinnae glaucous blue-grey beneath.” The sori of D. linearis are globose, yellowish and are produced in a single row on both sides of the costules (ridges); the spores within the sori are minute, more or less glassy or translucent (hyaline). D. linearis sometimes grows as a thick mat of strong stems and wiry fronds, forming a tough barrier to move through; these fern clumps burn relatively easily due to an accumulation of dead stems and leaves. In fact, D. linearis is one the few branching ferns that can quickly develop into and almost impenetrable thicket up to 2 m (6 ft) or more in height, shading out all other plants. It can grow up on to trees, reaching heights of 7 m (22 ft) or more with its slim fronds meshing together, making it more or less impossible to move through.
Distribution: Dicranopteris linearis is an indigenous native fern common in many disturbed areas or secondary forests in tropical or subtropical areas of tropical Africa to the Indian subcontinent, as well as in tropical China, Southeast Asia and parts of Australia, New Zealand and the volcanic Pacific Islands. Where the “false staghorn fern” (D. linearis) is found, it is generally an indicator of very acidic soils. It is adapted to colonize forest margins or open ground, especially in poor or eroded soils where natural or human induced landslides or other forms of disturbance have occurred, and almost always in full sun. This fern can spread by spores or by it rhizomes via cloning scrambling along the ground and climbing on other vegetation, often forming thickets 3 metres deep or more. “The stem grows from the rhizome, branches at a 45° angle, and forms fronds that continue to bud and branch… [and this manner the fern’s “growth can continue for a long distance as the plant forms a mat, grows over itself in layers, and spreads” (Romanchak et al. 2005). From a positive point of view, this vine-like fern plays a significant role in stabilizing exposed soils, especially in areas of steep slopes and high rainfall. In fact, D. linearis forms a distinct indigenous vegetation type, designated as Dicranopteris fernlands (e.g., see Mueller-Dombois and Fosberg 1998; Merlin 1985, Maxwell 1982), and as such, it plays an important role in successional structuring the plant community in many humid tropical ecosystems. This includes the high islands of Micronesia where it is closely associated with open areas where this fern may develop into “very dense thickets” which are consistently kept more or less open by people setting fires; this “in turn prevents forest regeneration but also increases plant diversity in the savannas as it is hard for other plants to compete with Dicranopteris” (Costion and Lorence 2012:58):
“This fern species is …able to colonize and maintain dominance due to its shallow rhizomes, highly effective leaf area, and phosphorus use efficiency. [Dicranopteris linearis] fern is also known to contribute to soil organic matter in the form of leaf litter as soil nitrogen and phosphorus is returned to the poor soils common in tropical ecosystems” (Romanchak et al. 2005:517).
As noted above, the rapid, multilayered, clonal fern growth and specialized nutrient requirement of D. linearis also appears to help dampen the impact of alien invasive species by crowding them out and thereby can play a significant conservation role in preserving native species while enhancing ecosystem restoration over time:
“Growth form and nutrient use in Dicranopteris [linearis] render this species unrivalled in terms of its ability to vegetate harsh landscapes and maintain dominance by blanketing a site with leaves. Carbon gain in Dicranopteris [linearis] under nutrient-poot conditions can be substantial, resulting in important impacts on regeneration, ecosystem-level productivity, nutrient uptake, soil genesis and, consequently, ecosystem development” (Russell et al. 1998:778).
Slocum (2000) suggested that logs and fern patches (e.g., those dominated by Dicranopteris) could create a suitable condition and pathways for secondary species to colonize and help successional processes proceed, thus leading to the restoration of heavily disturbed or destroyed forest areas in the tropics. For example, Cohen et al. (1995) suggested “that disturbing (clean weed, root removal and till) Dicranopteris linearis fernlands soil could accelerate the germination of herb, shrubs and trees seeds,” however the seedlings recruited from these Dicranopteris “disturbed fernlands were dominated by herb, sedge, and grass species” not forest species (see Florentine and Westbrooks 2004). More research is recommended that focuses on the role and value of Dicranopteris linearis fernlands in independent or related soil stabilization and renewal, as well as its putative associations with tropical forest restoration.
General Human Uses: We discussed above how Dicranopteris linearis fern can spread rapidly in open disturbed areas, and therefore its growth is sometimes culturally encouraged or integrated into soil stabilization schemes, especially in steep landscapes. In addition to its community ability of impeding or at least slowing down rates of erosion, there are also a number of ethnobotanical relationships associated with the false staghorn fern, D. linearis. For example, in some tropical areas of its natural, widespread distribution, the pliant fibrous leaf stems (petiole and leaf axis) of D. linearis fern are traditionally woven together to make mattings, fish-traps, chair seats, thatching for walls and roofs, pouches, caps, and ropes. Indeed, the lignified peripheral fibres of the stem are used widely in Asia for plaiting. More than a century ago, in the spring of 1901, Professor Percy Wilson was commissioned by the New York Botanical Garden to accompany a solar eclipse expedition to the “East Indies.” His responsibility was to “obtain collections of native plants and plant-products for exhibitions in the museum of the Garden.” In the Proceedings of the Torrey Botanical Club for Wednesday, February 24, 1904, the paper presented by Professor Wilson in the monthly scientific program of that club was entitled: “Remarks on some Economic plants of the east Indies.” Wilson’s presentation was reviewed by Marshall A. Howe (1904), Secretary pro tem of the Torrey Botanical Club. In one short section of his review, Howe recorded Wilson’s description of how fine fibers of D. linearis used to make festival caps for Southeast Asians living on Singkep Island (south of Singapore and east of Sumatra in Indonesia) were extracted from the false staghorn fern:
“Fibers derived from the vascular bundles alone are obtained from the leaf-stalks of a common fern, Dicranopteris linearis. After the long bundles are split out from stalks, they are drawn separately through a series of holes of gradually diminishing sizes punctured in a piece of tin. With the strong fiber thus obtained fine hats are made which are worn by the Malay men at the various festivals” (Howe 1904:63, also Science May 1904: 793-794).
A variety of additional artifacts and material uses of the stems and fibers of D. linearis are described below:
“The whalebone-like pith that comes loose from the peripheral fibres is brittle near the base but flexible and resilient at the top and is used for pretty and elegant plaiting. Fishing-stakes, baskets and sometimes ropes have been made from the stems. They are quite resistant to salt water and therefore the fern is widely used in the construction of fish-traps where the stems last for about two years. The [people’s] caps (“songko”), used in northern Peninsular Malaysia and peninsular Thailand, are durable enough to last several generations. In Malaysia they are sometimes coated with wood-tar to make them more durable. In Papua New Guinea arm bands and belts are made from the stems and the plants are used for casual adornment. The very firm stems can be sharpened to a resistant point. In Malaysia they were shaped into pens ("kalam") used for Arabic calligraphy. The oldest and strongest stems make the best pens and they have also been used to make knives. In Indonesian nursery gardens entire leaves are put upright in the ground to shade young crop plants. By the time the young plants can stand exposure to direct sunlight, the fern leaves have wilted and shed their foliage” (https://uses.plantnet-project.org/en/Dicranopteris_linearis_(PROSEA).
In addition to many material uses, in some regions, young rachises of D. linearis ferns are eaten after boiling and/or other parts of this plant are also reportedly used for medicinal purposes, e.g., as an antiasthmatic, a febrifuge and for poultices intended for a number therapeutic applications. Zakaria et al. (2008:179) gave aqueous extracts of D. linearis “leaves” to experimental animals test the antinociceptive, anti-inflammatory, and antipyretic properties of this fern; and in their conclusions, they determined that “the aqueous extract of D. linearis has antinociceptive, anti-inflammatory, and antipyretic activity, supporting previous claims of its traditional use by the Malays to treat various ailments, particularly fever.” (also see Toji et al. 2007). However, due to reports of arsenic content in this fern, large doses of this common plant are not advised as they may be harmful to humans. Srivastava (2007) reported some additional regional uses for D. linearis ferns:
“Young circinately vernated leaves mixed with cow milk used seven days continuously to remove sterility in women. Petiole and racheae are used in thatching the huts and widely sold as writing pens (India). Crushed leaves are applied as a poultice to control fever (Malaysia); the plant is used to get rid of intestinal worms (Indochina); to treat boils, ulcers and wounds (New Guinea)” [for additional references to medicinal use in tropical Asia and elsewhere also see Vasudeva 1999; Upreti et al. 2009; Bosch 2011; and https://uses.plantnet-project.org/en/Dicranopteris_linearis_(PROSEA)].
In Remote Oceania, beyond Micronesia, there are references to traditional uses of D. linearis ferns According to Pukui (1983), a kind of Hawaiian tea brewed from the fronds of uluhe fern (D. linearis)was imbibed traditionally by Hawaiians as a laxative; and “Shore-dwellers of Ka'u on the island of Hawai 'i applied the derisive term pala uluhe (ripened in uluhe leaves) to poor upland farmers, who ripened bananas in pits lined and covered with uluhe leaves, rather than allowing them to ripen in the field” (also see Cambie and Ash 1994 for traditional medicinal use references for D. linearis in Fiji, as well as a listing of the chemical compounds identified from samples of this fern; in addition, see Baltrushes 2006 for a reference to traditional medicinal use on Moorea Island).
Uses in Micronesia:
Uses in Palau: Kitalong et al. (2011:75) in their survey of plants, people and culture in the villages of Oikull and Ibobang on Babeldaob, the largest island in Palau, reported the use of “Dicranopteris linearis var. ferruginea” in an “herbal drink.” Known locally as “itouch” in Palau, parts of this “variety” of D. linearis are mixed with components of several other plants, to produce this beverage, which is imbibed as “part of the Modekngei religious ritual.” In this ceremony, participants come together “on special dates to worship” and to consume this liquid concoction “that cleanses the body.” Some of the plant species (and, in some cases, their Palauan names) that are reportedly used to make this drink, as told to Kitalong and her colleagues by their informant, M. Ngirametuker, included “Dianella carolinensis (kebesos), Phaleria nisidai, Melastoma malabathricum L. var. mariannum, Nepenthes mirabilis, Lycopodiella cernua (olechuila beab), Dicranopteris linearis var. ferruginea (itouch), Cassytha filiformis (tellelachull), Trema cannabina Lour. (chelodechoel) and Hedyotis korrorensis (chemudalech).”
Uses in the Mariana Islands: Moore and McMakin (1979) described Dicranopteris linearis fern, known as Mana in the native Chamorro language of the Mariana Islands as a low growing and quickly spreading plant, that is an important soil binding pioneer species which very quickly volunteers after a natural or human-induced land slides, other form of erosion, or following a forest fire. Earlier, Stone (1970:21-22) referred to one of his vegetation types on Guam as the “Erosion Scar community” made up of pioneer species; Stone listed Dicranopteris linearis as the first of about 15 characteristic species that naturally occur in this community. As we pointed out above, D. linearis ferns often grows into thick, pure stands that can cover an erosional scar and hold the soil together until other species become established through succession. Kirch (2017:156) citing Athens and Ward (1995) referred to the Pago Valley on Guam where suggestive charcoal particle evidence of human burning as early as 1600 B.C., with interpretation of ancient pollen samples cored from the valley showing “marked reductions in forest trees and increases in the fire-adapted fern Dicranopteris linearis, a classic signal of anthropogenic disturbance on oceanic isands.”
Uses in Chuuk: Human-induced Dicranopteris linearis grasslands on the high islands of Chuuk, as on Yap and Pohnpei, are relatively extensive, and reportedly increasing in area because of frequent burning which destroys the forest edge and tree regeneration. Dominant Three grasses, Paspalum, Dimeria, Ischaemum, along with the false staghorn fern D. linearis dominate these largely man-made vegetation communities (see the 1997 Climate Change National Communication, http://www.un-gsp.org/sites/default/files/documents/micnc1.pdf). In the past, D. linearis fern, was used in local Chuukese medicine, and parts of this plant are now sometimes hung up for Christmas decorations in Chuuk.
Uses in Pohnpei: Perhaps because of its natural toughness Dicranopteris linearis fern, known on Pohnpei as Mwedil en mal (or Dipwinmall and Limwedilinmall) is used as a source of spiritual protection for a house when it is being built. According to a local informant, on Pohnpei this fern is used “at local dances in mwaramwar (head garland or lei), a stem (with leaves) the circumference of the person’s head is wrapped in a circle and tied around the head” (see Balick et al. 2009). D. linearis fern is also reportedly used as an emergency sun hat or decoration on Pohnpei (e.g., see Lee Ling N.D.). According to the online Pohnpeian-English dictionary, “Dicranopteris linearis false staghorn fern, traditionally [is] placed in the home and inserted in thatch to prevent roach infestation; [it is] also used to make mwaramwars” (see http://www.trussel2.com/PNP/finderd.htm).
Uses in Kosrae: Although little ethnobotanical information has been identified for Dicranopteris linearis fern on Kosrae Island, the following biogeographical and ecological information on this plant was offered by Maxwell (1982:119):
“On exposed peaks and ridges included in the Elaeocarpus carolinensis-Cyathea ponapeana type is a community type dominated by the fern species Dicranopteris linearis (Fig. 1). This is described by F. R. Fosberg (1960) as ‘dwarf vegetation on open crests.’ Occasionally, stunted Elaeocarpus carolinensis and Astronidium kusaianum appear, but they are essentially the only remnants of the lower types. Other ferns and fern-like plants found were Blechnum orientate and Lycopodium cernuum. Where the ground is not thickly covered by the fern Dicranopteris linearis, deep tussocks of moss occur. High rainfall and exposure to high winds are probably the main determinants of this community type.