Micronesan Names by Islands or Island Groups: Roro or Rorou (Palau), Hawhow (Palau–Tobi Island), Rarr, Raar or Paar (Yap), Paar (Woleai), Gaogao, Gabgab or Gapgap (Mariana Islands), Paar, Weeku (Chuuk), Parepein, Pahr (Pohnpei)

Description: The genus Erythrina in Fabaceae, the bean or pea family, comprises of about 110 species of trees and shrubs. The name “coral tree” is used as a collective term for all these Erythrina plants. Erythrina variegata, described here,is a fast-growing, spreading tree with a wide distribution (see below) including many tropical Pacific islands [note: Falanruw 2015:106, and others have identified the coral tree found in Yap, the Mariana Islands and other Micronesian Islands as Erythrina variegata var. orientalis (L.) Merr.]. If the environmental conditions are favorable, E. variegata it may grow at “rates greater than 1.5 m (5 ft) per year” (Whistler and Elevitch 2006b). As a full grown tree it can reach up to 20 m (65 ft) in height with a thorny trunk and branches. The trifoliate leaves are arranged alternately and are 6-25 cm (2-10 in) in length on long petioles. Clusters of dark to scarlet red flowers with very unequal petals are produced in long, dense stalks (racemes) at the leaf axils. The fruits are curved, linear to oblong pods, 12-22 cm (5-11 in) long and contain 3-10 hard, kidney-shaped seeds about 1.5 cm (0.5 in) long. Another much less common Erythrina species found in some areas of the tropical Pacific is Erythrina fusca Lour. Which differs from E. variegata by the rounded tips of its leaflets and the darker, nearly purple flowers; E. fusca is reportedly found in swampy areas in some parts of Micronesia on the islands of Palau, Yap, Kapingamarangi, Pohnpei and Kosrae, as well as in North Malaya (Falanruw 2015:106). An endemic species of Erythrina restricted to the Hawaiian Islands, Erythrina sandwicensis Degener, is referred later in the discussion below.

Distribution: The coral tree, Erythrina variegata,is found from Zanzibar, off East Africa, to eastern Polynesia, occurring on most of the high islands of Polynesia and Micronesia, especially on atolls, although it may have been introduced on some islands, e.g., Pohnpei where a variety referred to by some as the “wild type” (e.g., see Whistler and Elevitch 2006b) with leaves that are mottled with yellow color (Erythrina variegata var. orientalis (L.) Merr.). E. variegata is usually found in coastal forests, more commonly on the outer atolls, but also on the rocky shores of high islands, and occasionally inland in lowland and ridge forests; it normally grows in sandy or limestone soils up to 250 m (800 ft) in elevation.

General Uses and Problems: Cultivated widely in tropical regions of the world, Erthyrina variagata is a valuable, multipurpose tree, often grown as an ornamental tree and for soil improvement as a nitrogen fixing species (typical of Fabaceae species). As a fast growing species, it is also used to shade understory tree crops such as coffee and cacao. In addition, the coral tree is used commonly as a boundary marker, living fence post, trellis support, windbreak, animal fodder, and outrigger float; the latter use is due to its light wood. In addition, in some areas, parts of E. variegata are used for medicinal purposes (e.g., see Whistler and Elevitch 2006b). It is even reported that the “young, tender leaves and young sprouts [of E. variegata] are eaten as a vegetable” (e.g., see Fern 2018). In Hawai’i, E. variegata is known as “wiliwili-haole,” indicating that it is a foreign tree in those islands, but is closely related to the endemic Hawaiian E. sandwicensis. Indeed, in the Hawaiian Islands, the “Tropic Coral” variety of E. variegata, is a common landscape tree where its tall, artificially selected columnar form (known locally as “tall erythrina” or “tall wiliwili”) is used as fence posts and windbreaks, for soil and water conservation, and for planting around farms (see Rotar et al. 1986). Although the wood of E. variegata is a poor choice for non-living fence posts, because its wood is not particularly resistant to rot, “if a living fence post is desired, E. variegata is excellent for this purpose” (Whistler and Elevitch 2006b:10). Early in the 21^st century, a gall wasp insect (Quadrastichus erythrinae), was identified as a new species recorded from Southeast Asia and the tropical islands of Mauritius, and Reunion in the Indian Ocean. Following recognition of this pest insect, damages to Erythrina coral trees were reported from Taiwan, China, India, Philippines, American Samoa, Guam, Okinawa and the Hawaiian Islands. In Hawai’i, this gall wasp was discovered first on O’ahu in April 2005, from where it spread rapidly to the other islands in this archipelago where it injures not only the introduced E. variegata (including the “tall erythrina” variety), but also other Erythrina species including the native endemic “wiliwili,” E. sandwicensis Degener. This endemic Hawaiian coral tree has been regarded as a “keystone tree species” in the few remaining low elevation dryland forests or remant patches of this heavily human-altered type of terrestrial ecosystem in these islands (e.g., see Kaufman et al. 2013:72). Hopefully, more recent biocontrol efforts offer some optimism for the survival of these naturally and culturally significant species. Indeed, after a rigorous risk assessment by government biologists in Hawai’i, a biological control agent, Eurytoma erythrinae, collected in Tanzania, Africa, was released in the Hawaiian Islands in 2008. “Regular sampling and gall dissections showed that the wasp became established within 6 months of its release. Results from post-release monitoring indicate that E. erythrinae is successfully controlling gall wasp populations in foliage at most sites, whereas infestation levels in inflorescences remain still high at some sites. Surviving wiliwili trees are recovering from gall wasp damage. Post-release monitoring continues in order to determine the impact that E. erythrinae will have on the species’ long-term viability (Kaufman et al. 2013).  Kumar et al. (2010:147-152): reviewed the phytochemistry and pharmacological aspects of E. variegata:

“Erythrina variegata has a “wide range of chemical compounds have been isolated, mainly alkaloids, flavonoids, triterpenoids, and lectin. Different parts of the plant have been used in traditional medicine as nervine sedative, collyrium in opthalmia, antiasthmatic, antiepileptic, antiseptic, and as an astringent. The alkaloids extracted from the leaves of E. variegata are reported to have anti-inflammatory and analgesic activity. Isoflavonoids isolated from E. variegata having antibacterial and anthelmintic activity. E. variegata shows several other characteristic pharmacological effects like neuromuscular blocking, smooth muscle relaxant, CNS depressant, and hydrocholeretic, which are consistent with the reported uses of the plant extracts in the indigenous system of medicine. Hence the present article includes the detailed exploration of morphology, phytochemistry, and pharmacological aspects of E. variegata in an attempt to provide a direction for further research [also see Lahari et al. 2015].”

Interestingly, ethnobotanical research in Vanuatu and New Caledonia indicated that ciguatera poisoning has been treated by macerating the stembark of Erythrina variegatawith the bark of Pterocarpus indicus, mixing the ground up residue with water, and then drinking the mixture (Bourdy et al. 1992:168; also see Rageau 1973).

Uses in Palau: On remote Tobi Island (Hatohobei in Tobian language), located in the southern region of the Republic of Palau, Hawhow(Erythrina variegata) is reportedly used medicinally in combination with other plants for more than one medical ailment. Black (1968) describes some of the issues to be dealt with when seeking traditional knowledge of medicine on Tobi which has relevance to many other Micronesian Islands:

“[On Tobi it] seems to be that medicine, like fishing lore and magic, is very private property. Today, anyone needing medicine for himself or his family goes to whoever is known to possess medicine able to cure his illness. This person, if he agrees to help, then collects and prepares his medicine in secret and administers it. The payment is usually one coconut tree. There are two aspects to this problem: secrecy and payment” (see Black 1968 for how Hawhowand other plant species are reportedly used medicinally on Tobi).

Uses in Yap: The wood of Erythrina variegata is very light, and thus used in tropical Pacific islands such as Yap to make fishnet floats and firewood. It flowers from July to September after dropping most if not all its leaves, and is sometimes used as a seasonal indicator; for example, in Yap, when this tree is flowering, the sharks are said to bite bait. Compare this saying with one associated with the Hawaiian “wiliwili” tree (the endemic Erythrina sandwicensis): “A pua ka wili-wili, A nanahu ka mano” (When the flowers of the wili-wili tree, that is the time when the shark-god bites, e.g., see Emerson 1909:221). Also compare this empirical regularity recognition with a traditional Samoan saying: “When the coral tree [E. variegata] fruits are ripe, it is an indicator that whales are running and yams are in season in Samoa” (Whistler and Elevitch 2006b:11). E. variegata is reportedly also used in Yapese medicine; according to Okabe (see Defillips et al. 1988:16), in “Maap” District it is used “for stomachache, leaves and bark are finely cut, and the pressed out juice is drunk twice daily” and in “Ugiri” District it is used “for dyspepsia, the shaved bark is crushed together with the young leaves of Ophioglossum pendulum [Ribbon Fern] and taken three times a day with coconut milk.”

Uses in Mariana Islands: More than a hundred years ago Safford (1905:270) noted the use of the light wood of the fast-growing Coral Tree, known locally as Gaogao (or Gabgab), in the Mariana Islands to make water containers and living fences:

“In Guam the light soft wood of Erythrina variegata has been used for making troughs. Stakes thrust into the ground readily take root, so that the natives use them for making the enclosures about their gardens.”

Today in the Mariana Islands, E. variegata, is used as an ornamental and shade tree, as well as a resource for firewood and medicine:

“This tree is often planted for its showy flowers which appear during the dry season after the leaves have fallen. The leaves are used as supplementary ingredient in the all-purpose medicinal tea of one of the local suruhanos [traditional curers]” (Moore and McMakin 1979:154; also see McMakin 1978:13).

In addition, E. variegata has general wildlife importance. For example, its flower nectar is consumed by birds, bats and snails (e.g., see Larones 2104a, Craig 1989, Hadfield 2010). In addition, according to Brooks (2018), the rare, but culturally significant bat species Pteropus marianus (known as Fanihi in the Mariana Islands), has been observed roosting in E. variegata trees located on Anderson Airforce Base on the island of Guam; and besides roosting in E. variegata trees, the P. marianus bats are known tofeed regularly on the tender young leaves, shoots and buds of these trees; indeed, these tender parts of the coral tree are important food sources for the bats after damaging typhoons which are relatively common in the general Western Micronesian region. Oher native animals in the Mariana Islands that utilize E. variegata trees are the endemic land snails; for example, Hadfield (2010) reported on the snail habitat preferences and abundances on remote Pagan Island in the Northern Mariana Islands, with comments on the threats to the native snails and the coral trees themselves:

“One of the main host trees for the snails is Erythrina variegata var. orientalis, supporting many tens to hundreds of snails on the trunk and leaves of a single tree. Unfortunately, these trees are being attacked by the same Erythrina gall wasp, Quadrastichus erythrinae Kim, that has devastated the native Hawaiian Erythrina sandwicensis…. In order to preserve the Erythrina in the Mariana Islands, and the important snail habitat that they provide, we strongly recommend exploring the possibility of introducing the Erythrina gall wasp biocontrol agent, the wasp Eurytoma erythrinae, used so effectively, to date, in Hawai`i (S.E. Miller personal communication with Neil Reimer, October 2010).

Uses in Pohnpei: Glassman (1952:25) referred to “Erythrina” as one of the “woody strand plants most likely to be seen” in the vegetation near the shorelines of Pohnpei Island. There are two closely related species of Erythrina found on Pohnpei today, E. fusca (Paramwahn) and E. variegata (Parepein or Pahr). From an indigenous perspective, the Pohnpeian names of these two Erythrina spp. indicate that Pahrmwahn is male (mwahn) and Pahrpein is female (pein).  Pahrmwahn and Pahrpein have interchangeable uses. Their leaves are reportedly pounded and used to make a drink to cure curses. The leaves, bark, and roots of these Erythrina trees are burned on red hot stones and then the cursed person, with a cover over their head, breathes in the smoke from the smoldering parts of these trees. The leaves are also wrapped around rock and placed where a new house is to be built to make the work easier (an association with the light wood of these trees) and to protect a new house structure (see Merlin et al. 1992:29-30). Also see Balick et al. (2009:386-387) for additional therapeutic uses for E. variegata on Pohnpei; for example:

“To make a heat treatment for nerve damage that may have been caused by sorcery (a treatment known as umwulap en kau) …. To treat rihpw (itchy swelling) on arms ….  To make a heat treatment for nerve damage that may have been caused by sorcery (a treatment known as umwulap en kau) …. To treat rihpw (itchy swelling) on arms….”

Glassman (1952:21) noted that wood from “Erythrina (pahr), Hernandia (pinapin), and Thespesia populnea.” was sometimes used in canoe construction, but these tree sources “are not so highy prized” as the most important ones which he identified as “Campnosperma brevipetiolata, Elaeocarpus carolinensis, Xylocarpus granatum (plock), Parkia korom (kurum), and breadfruit, in that order.

Uses in Nauru: According to Thaman et al. (1994:147-148) Erythrina variegatavar. orientalisa variety of the Coral Tree that is native to Nauru Islands where it is planted or spontaneous in coastal strip as well as “in old strip-mined land” and in the past the trunks and thick branches of this tree were used to make “living fence posts, and in canoe construction” and the flowers used in garlands; in contrast, Erythrina variegata L. var. variegata, is a recently introduced species and occasionally planted as an ornamental on Nauru.”