The karuka (Pandanus julianettii, also called karuka nut and Pandanus nut) is a species of tree in the screwpine family (Pandanaceae) and an important regional food crop in New Guinea. The nuts are more nutritious than coconuts, and are so popular that villagers in the highlands will move their entire households closer to trees for the harvest season.
Description The species was originally described in 1908 by Ugolino Martelli from only a few drupes in the collections of the Royal Botanic Gardens, Kew He was hesitant to describe it as a new species from only that, but the characteristics were so salient he published his description. The tree is dioecious (individual plants either have male flowers or female ones), with male trees uncommon compared to females. It reaches 10–30 metres (33–98 ft) in height, with a grey trunk of 30 cm (12 in) in diameter and supported by prop roots or flying buttress roots up to 12 m (39 ft) in length and 15 cm (5.9 in) or more in diameter. The trunk has white mottling and is generally smooth with occasional warts or small knobs as well as rings of leaf scars. Inside the trunk is pithy and lacking cambium. The top of the tree sometimes branches, producing three or four crowns of leaves. Each crown will produce a single cluster of nuts, typically once every other season. Production is affected by the seasonality of local rainfall. Leaves spiral up the trunk in opposite pairs. The large leathery leaves are 3–4 m (9.8–13.1 ft) long and 8–12 cm (3.1–4.7 in) wide. The apex of the leaf is attenuate and doubly-pleated, with prickles pointing up at the tip and along the margins and midrib. The leaves are dark green on top and dull cyan underneath. The inflorescence on male trees is a densely-branched spadix with a dozen long spikes, each containing many staminate phalanges. In each phalange is a column 3 mm long topped by up to 9 subsessile anthers. The male flowers are white, and the whole male flowering organ may be up to 2 m (6 ft 7 in) long. The pollen has a psilate exine (unornamented outer wall) 0.8 μm thick. The ornamentation is granular between echinae (short spines). The ulcerate aperture is 3 μm in diameter. Pollen grains measure an average of 30 × 14.5 μm in size. On female trees, the inflorescence is a single ellipsoid or ovoid syncarp, or fruiting head, with off-white bracts. Female flowers can produce fruit without pollination, and are typically the only trees cultivated. The tree stops making leaves when new fruit is growing. The syncarp has up to a thousand densely-packed single-celled carpels that later turn into drupes. The clavate, pentagonal drupes measure up to 12 cm (4.7 in) long and have a sharpened base, but typically are 9×1.5 cm, and are a pale blue-green colour. Each cluster contains about 1000 nuts. The endocarp is bony and thin, 5½ cm long, with rounded edges about 1½ cm wide. The seed-bearing locule is around 4 cm (1.6 in) long. The core of the mature head (mesocarp) has an appearance like honeycomb and is spongy and pink. The top of the mesocarp is fibrous, from 3 cm (1.2 in) long and up. Though Martelli did not have a complete syncarp, he knew the cluster of fruit must be large, estimating at least 30 cm (12 in) in diameter. He was correct, as the fruiting cluster is typically 15 to 30 cm in diameter. A mature head and stalk weigh up to 16 kg (35 lb), but average 6 kg (13 lb). but weights up to 27 kg (60 lb) have been reported. It most closely resembles P. utilissimus, which is found the Philippines. People also harvest and eat nuts of P. antaresensis, P. brosimos, P. dubius, P. iwen, and P. limbatus, and P. odoratissima
Names The specific epithet "julianettii" honors naturalist Amedeo Giulianetti, who found the original type specimens. Karuka is a loanword from Tok Pisin. Sometimes the tree is called 'karuga' or 'karuka nut pandanus'. The term 'karuka' can apply to both Pandanus julianettii and P. brosimos, though the latter is usually called 'wild karuka'. Both species, as well as P. dubius, can be called 'pandanus nut'. In addition to P. brosimos, 'wild karuka' can also refer to P. antaresensis, P. iwen, and P. limbatus, but nuts from these trees are a much smaller part of the local diet. In contexts where multiple karuka species are discussed, P. julianettii is sometimes termed 'planted karuka'. P. julianettii, P. iwen, and P. brosimos are also in the subsection named Karuka, which is in the monotypic section also named Karuka. In New Guinea it has different names among each of the Papuan peoples. In the Ankave language it is xweebo. It is yase in the Baruya language. The Huli language word is anga, and it is also anga in the Duna language. In Kewa language it is aga, but it is unclear which dialect(s). In the Kewa pandanus language it is rumala agaa. The Kalam language term, in both standard and pandanus languages, is alŋaw, but it can also be called kumi or snay. The plant is called ama in the Wiru language. In the Pole language it is called maisene. It goes by ank in Angal language, and aenk in the Wola dialect. The Imbongu language word is amo. The plant also has many names on the other half of the island. In Indonesian it is called pandan kelapa (lit.coconut pandan) and kelapa hutan (forest coconut), but these names can also refer to P. brosimos and P. iwen. According to field research by Kiwo et al. in Melagineri District, Lanny Jaya, the Lani people call it gawin, with woromo for P. brosimos, owandak for P. iwen. Meanwhile according to field research by Zebua et al. in Pirime District, Lanny Jaya, woromo is used to refer to P. iwen, while in another study in Jayawijaya, the Lani used woromo for P. julianettii with the Dani people call it tuke, hence the names have been used interchangeably by multiple publications from different regions and might be a separate species in the complex.
Cultivars There are up to 45 cultivars of karuka, many with different kernel shapes. There are likely many more, as some are known only to a small number of people in a single settlement. 'Tabuna' and 'Henga' are some of the most important. 'Tabuna' is popular because it is high-yielding, tastes good, and has no taboos on who/what can eat it and how/if it is cooked. At least two varieties are edible raw. Named varieties include:
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