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Introduction
*Kawasusu in Polynesia: Tephrosia purpurea
*The art of stunning fish
*Kawasusu in Aotearoa: Pittosporum tenuifolium
Kōhūhū in Te Ao Māori
Gallery
Further Information and Credits
This is an intriguing word, and the links between its tropical Polynesian and Māori reflexes are tenuous, but taking them at face value enables us to learn something about two interesting albeit apparently quite different plants. The tropical Polynesian Kavasusu / Kohuhu is a herb or short-lived "subshrub" probably introduced in the first wave of immigration from the Central Pacific and spread thrughout Polynesia because of its usefulness in stunning fish. The Māori kōhūhū is a very different kind of plant, a small forest tree with a very much longer lifespan and (apart from its being a plant with a somewhat similar name) apparently having nothing in common with its tropical counterpart. Perhaps just the fact that many parts of the plant had a common use was sufficient similarity -- the roots, leaves and stems of the Tephrosia are useful for stunning fish, and the leaves, flowers, branches and gum of the Pittosporum provide a leasant fragrance for preparing a place for guests and other purposes. Or perhaps the seed capsules of the Pittosporum reminded some early explorer of the rolled-up balls of leaves and twigs used as a fish anaesthetic. Whether the names are cognate or simply alike, the plants they name have proved interesting and useful to the people who have encountered them.
*Kawasusu in Polynesia: Tephrosia purpurea.
 In his Useful Tropical Plants database, Ken Fern describes Tephrosia purpurea as "an extremely valuable species, usually divided into a number of subspecies, though many subclassifications exist". The Polynesian plants are generally assigned to the subspecies purpurea. The species is native to a wide area from the northeast tip of South America through Africa to India, Southeast Asia and China to New Guinea. The "World Flora Online" database lists it as native also to Western Polynesia, but Art Whistler (Plants of the Canoe People, p.205) regards it as an ancient introduction to all of Polynesia. Throughout tropical Polynesia (and at least as far west as India) it was used in fishing, to render fish senseless so they could be easily caught. The active ingredient, tephrosin, stupifies fish but has no effect on people (or other mammals). It also has insecticidal and possibly anti-cancer properties.
In Polynesia the plant is found from sea level to about 300 m. on high islands, mostly in rocky places. It was once cultivated in many parts of its Polynesian range, but now rarely so. It is a shrubby, fairly deep-rooted annual or perennial growing to a metre or a bit more in height. The leaves consist of sets of 7 - 13 leaflets arranged in pairs with a single leaflet at the top, each 1 - 3.5 cm long, oval, acute at the base and notched at the tip, on very short petioles. The inflorescence (illustrated above, left) consists of racemes of several flowers, at the ends of branches or opposite leaf stalks, with butterfly-like flowers, purple or white with a purplish or pink interior. These produce narrow, straight brown or straw-coloured pods 3-5 cm long which twist apart when mature. Each has 5 - 9 dark, oblong seeds about 3.5 mm long. Apparently the seeds can be used as a substitute for coffee. In Hawai'i the plant was also used medicinally, for various skin ailments, ringworm and rashes. Outside Polynesia it has a variety of medicinal uses, including as an antidote for snake bite and for treating various intestinal problems. Like many leguminous plants, the roots in conjunction with certain bacteria develop nitrogen-fixing nodules, which can also assist the growth of neighboring plants, as well as making the plant a useful source of green manure. It has also been found useful in reducing the salinity of saline soils.
The art of stunning fish.
Tephrosia purpurea was traditionally the favourite plant in Polynesia for use in stunning fish, but there were several other species also employed for this purpose. All of them were anaesthetics rather than poisons. More lethal species were introduced in the nineteenth and early twentieth centuries, but like dynamite, also introduced in this period, they are all now banned. The Tephrosia leaves, stems and roots were crushed with rocks or with a mortar and pestle, and the macerated bits rolled into balls and placed on coral heads or simply scattered in tide pools. After a few minutes the fish floated to the surface and were easily collected. This was probably primarily a way of securing bait or a quick snack, as the fish in tide pools are mostly small.
The other species traditionally used for this purpose were the ground seeds of the futu (Barringtonia asiatica), and various parts of the "poison vine" (fue 'o'ona in Samoa), Derris trifoliata. In Hawai'i, the endemic 'Ākia (Wikstroemia spp.) was also used, alongside the Tephrosia ('auhuhu).
 Derris trifoliata, pictured on the left, is a woody, high climbing vine native to Samoa and other parts of tropical Polynesia (its natural range is from East Africa to Micronesia and Mangareva). Like the Tephrosia, it is also a member of the Fabaceae. The flowers are borne in panicles 25 cm or more long with pink or white "butterfly" flowers. The fruit is a flattened, slightly rounded pod 3 - 4.5 cm long with one or two seeds. Like the Tephrosia it is a mild anaesthetic rather than a poison for fish. The crushed leaves and stems were rolled into balls and placed on coral heads in the targeted rock pools. Only in the early 20th century was the more potent (and now illegal) Derris malaccensis introduced from New Guinea for harvesting fish.
In Hawai'i the mashed roots and stem bark of the 'Ākia were used in a similar way to the other "poisonous" plants. The 'Ākia comprise the ten endemic species of shrubs and small trees of the genus Wikstroemia (Thymelaeaceae). The levels of alkaloids differ among the species; some may be poisonous to people as well as fish. These plants in Hawai'i were also a valuable source of fibre for ropes and braids, and possibly at times also for making kapa (tapa).
*Kawasusu in Aotearoa: Pittosporum tenuifolium.
The kōhūhū of Aotearoa, Pittosporum tenuifolium, is a tree growing 8 or 9 m. tall, with a slender trunk 30-40 cm in diameter and dark bark. Apart from having a somewhat similar sounding name, its links to the Polynesian Tephrosia are difficult to discern. However, it is listed as cognate with the Eastern Polynesian names in the Pollex database, and it inclusion gives us good reason to look at Polynesian methods of stunning fish as well as featuring a tree endemic to Aotearoa which is now widely grown internationally.
 The branchlets and young leaves of Pittosporum tenuifolium may be covered with short hairs. The oblong or somewhat oval shaped leaves may be anything from 1 to 7 cm long by 5 mm to 2 cm wide, alternating on the stems with short petioles. They are glossy pale-green above and lighter below, slightly leathery and with wavy margins. The fragrant flowers (the aroma is particularly noticeable and widespread in the evening) are either solitary or come in bunches on short stalks. They have very dark red, often almost black (or occasionally yellow) petals about 1 cm long, spreading and reflexed. The fruit is a somewhat woody 2-valved capsule about 1 cm in diameter and almost black when mature, splitting to reveal glossy black seeds with the sticky mucus typical of species of this genus. Some trees have either male or female flowers, others both, while there may also be entire (bisexual) flowers on particular trees.
The tree is found in coastal and lower montane forest throughout the North Island and in the north and east of the South Island. It is not evenly distributed, however. In the Waikato, for example, it is present in the Pirongia forest where it has been the key host species in attempts to reintroduced the mistletoes Tupeia antarctica and Ileostylus micranthus (DOC report 2023). It is not mentioned as a significant species in either the Botany of the Waikato (Clarkson et al 2002) or the survey of significant natural areas of the Waikato by van der Zwan and Kessells (2017). The tree is, however, widely cultivated as an ornamental plant, and has been found to be useful generally in stream stabilization projects and in restoring forest margins and regrowth areas. Peter de Lange notes in the NZPCN database page for this species that it "prefers successional habitats": according to Alan Clarke (2007) it was one of the trees like the whauwhau (Pseudopanax arboreus) that invades and replaces exhausted patches of aruhe (pig fern). However it is also found in the forest interior, where it is a tall, straight-trunked tree, in contrast with the forest edge or more open places where it is a compact tree much-branched from the ground upwards.
The species itself is very variable, and is known to hybridize with several related species: Pittosporum crassifolium, P. colensoi, and P. ralphii. L.J. Metcalfe, in his book on the Cultivation of New Zealand Trees and Shrubs notes that this has given rise "to an extremely motley assortment of seedlings". Some of these, often with attractively variegated leaves, have had considerable commercial success in New Zealand and overseas (various cultivars are grown in Great Britain, California and Tasmania). They are sometimes used as hedging trees but more often as specimens. He describes nine named cultivars in his book (p. 224); there are many more. This variability and tendency to hybridize may also partly account for the plethora of Māori names (kōhūhū is the one most often used, and some, like rautāwhiri, describe particular uses of the plant).
Kōhūhū in Te Ao Māori.
Traditionally the kōhūhū had important ceremonial, cosmetic and possibly also some medicinal uses. Branches were used in many ceremonies for removing tapu. They were also used for waving people on to the marae (hence the alternative names rautāwhiri and pōwhiri). Medicinally, the leaves may have been used in remedies for bruising and also the relief of excema. Murdoch Riley (Herbal, p. 216) recounts that. it was an ill omen to leave a kōhūhū tree standing on a ground area to be cultivated unless every branch was lopped off. Failure to do so could result in the death of the worker and his wife.
Kōhūhū was one of the most important sources of useful gums (pia or ware) for making oils fragrant. The leaves were also used for this purpose. A hei tawhiri was a necklet including gum or material (Elsdon Best mentions pukeko skin and feathers in this regard) scented with kōhūhū leaves. "Taku hei tawhiri" was a term of endearment for an infant. The leaves and gum were also used for scenting the house if important visitors were expected, and their sleeping places if they were staying overnight. This is reflected in the saying:
He moenga rangatira he moenga kakara
He moenga ware he moenga haunga. (Elsdon Best, Forest Lore, p. 64)
(The sleeping place of a chief is sweetly scented; that of the commoner is malodorous.)
The gum was extracted
by bruising the bark of the tree. It was employed as a reusable chewing gum in conjunction with pūhā, as well as for scenting oil or as a scent in its own right. For the chewing gum, the pūhā was bruised or cut and the juice left to thicken before being combined with the gum. Gallery.
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