Corynocarpus laevigatus

Corynocarpus laevigatus, commonly known as karaka or the New Zealand laurel, is a medium-sized evergreen tree in the family Corynocarpaceae. It is endemic to New Zealand and is common throughout the North Island and less common in the South Island. C. laevigatus individuals are also found on the Chatham Islands, Kermadec Islands, and the Three Kings Islands. C. laevigatus is mostly a coastal tree, although in the North Island, it is also found inland.

Corynocarpus laevigatus was first described in 1776 by the German naturalists Georg and Johann Reinhold Forster. C. laevigatus grows to heights of up to Template:Convert and has a stout trunk of up to Template:Convert in diameter. Its leaves are leathery, dark to bright green in colour and up to Template:Convert long. From August to November, C. laevigatus produces large oval-shaped orange-coloured fruits, about Template:Convert in length. C. laevigatus seeds are highly toxic to humans and contain poisonous toxins and other glucosides of 3-nitropropionic acid. The fruits are a valuable food source for the kererū (Hemiphaga novaeseelandiae) and the Chatham Islands pigeon (Hemiphaga chathamensis). C. laevigatus has been introduced to the United States for reforestation purposes; it is naturalised and considered an invasive species on several Hawaiian islands and is mostly found on the island of Kauai.

It is considered a (cultural treasure) amongst the Māori and Moriori peoples, who valued C. laevigatus for its drupes and seeds. On the Chatham Islands, depictions of Moriori ancestors were carved on to C. laevigatus trees (known as ) and are considered internationally significant and unique to their culture. An exoplanet originally named HD 137388 was renamed to "Karaka" in 2019 in recognition of the tree's orange-coloured fruit.

Description

Corynocarpus laevigatus (karaka) is a medium-sized evergreen leafy canopy tree with erect spreading branches. It is endemic to New Zealand. It grows to heights of up to Template:Convert and has a stout trunk usually up to Template:Convert in diameter, but can be up to Template:Convert in diameter. The largest trunk of a C. laevigatus specimen diameter ever measured was Template:Convert in diameter.Template:SfnmTemplate:Sfn Its bark is typically a grey colour.Template:Sfn C. laevigatus is predominantly a coastal tree, although in the North Island, it can also be found in lowland inland forests.Template:SfnmTemplate:Sfnm

Mature trees have dark brown corrugated bark with corrugations that are broken up into pieces that are roughly Template:Convert and Template:Convert thick. Younger trees have light brown bark that frequently has short, horizontal bands that resemble sewing stitches. C. laevigatusTemplate:'s dense shade and prolific seeding exclude local species and change the host community's composition and ecological processes in areas where it has been allowed to proliferate. C. laevigatus has an alternating elliptic oval-shaped foliage that are up to Template:Convert wide, with petioles less than Template:Convert long.Template:Sfn

From August to November, C. laevigatus produces large, stout, erect panicles of tiny greenish-yellow flowers, each less than Template:Convert in diameter. It starts flowering between August and November, and each panicle may have up to 100–200 flowers.Template:SfnmTemplate:Sfn Its sepals are rounded, and its petals are vaguely spoon-shaped (spathulate).Template:Sfn Each panicle on an inflorescence (flower cluster) can be up to 200 mm long.Template:Sfn The fruit C. laevigatus produces are oval-shaped and Template:Convert in length; with pale yellow–orange coloured flesh and a poisonous seed which is smooth and elliptic. The seed has an open system of fibrous veins on the yellowish surface.Template:SfnTemplate:Sfnm The fruit has a sickly sweet taste, reminiscent of apricots or dates.Template:Sfn Its leaves are dark green in colour, paler green beneath, thick, leathery, and are vaguely egg-shaped (obovate) to rectangular (oblong) in character.Template:Sfn

Corynocarpus laevigatusTemplate:'s wood anatomy prevents them from being dated using the conventional technique of counting annual growth rings in the trunk. C. laevigatus specimens planted in Palmerston North in 1962 grew to a height of Template:Convert in 42 years. The largest stem diameter measured Template:Convert, and the trees grew Template:Convert per year. Other C. laevigatus trees grew at different rates; the largest C. laevigatus tree in mainland New Zealand was 500 years old with a diameter at breast height (DBH) of Template:Convert and a growth rate of Template:Convert per year.Template:Sfn The fruits of C. laevigatus usually ripen between January and April and the seeds are mostly dispersed by two native columbiform birds, the kererū and the parea, which also feeds on its fruit. In modern-day New Zealand, the majority of C. laevigatus seeds germinate within Template:Convert of a parent tree, indicating that the tree does not normally spread out far.Template:SfnmTemplate:Sfn C. laevigatus has a diploid chromosome count of 46.Template:Sfn

Phytochemistry

At least 11 compounds have been identified in C. laevigatus. A unique nitropropanoyl glucopyranose called 1,4,6-tri-(3-nitropropanoyl)-β-D-glucopyranose (corynocarpin) was first identified and extracted by a 1978 study published in Phytochemistry.Template:Sfn A 2025 study examined the phytochemical screening of C. laevigatus extracts and revealed that the tree contains "significant amounts of phytochemicals".Template:Sfn

Gallery

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  Close-up of C. laevigatusTemplate:'s greenish-yellow flower panicle and characteristic leathery, oval-shaped leaves.
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  Clusters of C. laevigatusTemplate:'s fruit showing different ripening stages, from green to orange-yellow, hanging from branches with yellowing leaves.
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  Dense foliage of a mature C. laevigatus specimen showing its characteristic branching pattern and dark green, glossy leaves.
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  The trunk of a C. laevigatus specimen on Chatham Island; a Moriori dendroglyph can vaguely be seen in the centre of the trunk.

Taxonomy

Corynocarpus laevigatus was first described by the German naturalists Johann Reinhold Forster and Georg Forster in 1776. Despite this, their description was incomplete, and the figures of the flowers were inaccurate. The species was first described from specimens collected by Johann Reinhold Forster and Georg Forster on the second voyage of James Cook. Sir Joseph Banks and Daniel Solander, who were the botanists on the first voyage of James Cook, also brought specimens of C. laevigatus to England, where they described and published it under the name Merretia lucida, although their work was never formally published.Template:Sfn

Corynocarpus laevigatus is a medium-sized evergreen tree endemic to New Zealand, unlikely to be mistaken for any other native, foreign, or naturalised tree. C. laevigatus can be readily identified by its orange drupes and its leathery leaves.Template:Sfnm C. laevigatus is the only member of the family Corynocarpaceae found in New Zealand.Template:Sfn The four other species in the genus grow across the Pacific Islands and Australia, including: (C. similis) in Vanuatu, (C. cribbianus) in the Solomon Islands, North Queensland and Vanuatu; (C. dissimilis) in New Caledonia; and (C. rupestris) in the Australian states of New South Wales and Queensland.Template:Sfn

The Corynocarpus genus may have originated from a Paleotropical centre, then separated to two radiations into colder climates. In its first separation, C. cribbianus and C. rupestris were found in Australia through New Guinea, while in the second separation, C. dissimilis, C. similis, and C. laevigatus were found in New Caledonia, which led to New Zealand. Fossilised kernels from the genus Corynocarpus, from the early Miocene era, were found at Landslip Hill in the Southland Region, this discovery indicates that the genus has a long history in New Zealand. It is possible that the Corynocarpus genus spread from New Caledonia to New Zealand via land connections that existed in the mid-Tertiary era.Template:Sfn

Etymology

The etymology (word origin) of the genus Corynocarpus derives from the Greek , meaning 'club', and , meaning 'fruit', translating in English to 'club fruit'. The specific epithet (second part of the scientific name) originates from the Latin meaning 'smooth', in reference either to the fruit, the leaves or the skin.Template:SfnTemplate:Sfn In the Māori language, karaka can either refer to the fruit of the tree or the tree itself.Template:Sfn The word has origins in Proto-Polynesian languages. Cognates of karaka are used in Polynesian languages for members of the Planchonella genus, which share a similar appearance with Corynocarpus laevigatus.Template:Sfn Karaka is also the Māori word for the colour orange,Template:SfnTemplate:Sfn and has likely only been in use since the 19th century, as no word meaning orange appears in early Māori language dictionaries.Template:Sfn In the Moriori language and on the Chatham Islands, both the tree and the fruit are known as . This name may share an etymology with Polynesian names used to describe members of the true ginger genus, Zingiber.Template:Sfn In English, C. laevigatus is also commonly known as the "New Zealand laurel".Template:Sfn

Distribution

Corynocarpus laevigatus is found in large numbers throughout the North Island and South Island as far south as the Banks Peninsula on the east coast of the South Island and Greymouth, on the West Coast.Template:SfnmTemplate:Sfnm It is also found on the Chatham Islands, Kermadec Islands, and the Three Kings Islands.Template:Sfn Sources generally agree that before Polynesian arrival in New Zealand, C. laevigatus was likely restricted to the far north of the North Island, despite its current range across offshore islands and the northern half of the South Island, which was likely spread from Māori plantings.Template:SfnTemplate:Sfn Populations of C. laevigatus are often found in association with former pā (Māori village) sites.Template:Sfn In the far north of New Zealand, where kauri (Agathis australis) forests are the natural vegetation type, the density of C. laevigatus is low (about 2.5 stems per hectare). Populations can be significantly denser further south in the North Island, where C. laevigatus has spread from Māori plantings. A 2006 study by the New Zealand Journal of Botany indicated that the average canopy coverage across plots in C. laevigatus stands was 41%, with a maximum cover of 75%. Its estimated altitudinal range is between 29°N and 38°S.Template:Sfn Dense carpets of C. laevigatus seedlings can make it difficult for the natural regeneration of other species.Template:Sfn

The species was not naturally present in the Otago and Southland Regions of New Zealand prior to human settlement. All the individuals south of the Banks Peninsula are likely to be more recent horticultural introductions. The current population in Otago and Southland remains naturally uncommon and widely scattered along the coastline.Template:SfnTemplate:Sfn C. laevigatusTemplate:'s South Island population is exclusively located near coastal areas and most of the population is centred in the Banks Peninsula (including Christchurch's coastal areas) and the Marlborough Sounds.Template:Sfn C. laevigatus has been introduced to the United States, it is naturalised and considered an invasive species in Hawaii, where it is naturalised in moist soils and considered a threat to endangered or rare species such as Exocarpos luteolus.Template:SfnTemplate:Sfn C. laevigatus was introduced to Hawaii for reforestation purposes and was first naturalised to Kauai in 1891, and is still commonly found throughout the island.Template:SfnTemplate:Sfn C. laevigatus is primarily naturalised on the island of Kauai, it is also found on the islands of Hawaii, Molokai, and Oahu.Template:Sfn C. laevigatus is also grown in Southern California.Template:SfnTemplate:Sfn

Ecology

A kererū (a purple greenish white coloured bird) sitting in a fruiting karaka tree, surrounded by orange coloured fruits.

C. laevigatusTemplate:'s fruits are a valuable food source for the kererū

The fruits that C. laevigatus produces are a valuable food source for native New Zealand birds.Template:Sfn The kererū (Hemiphaga novaeseelandiae) and the Chatham Islands pigeon or parea (Hemiphaga chathamensis) are the only extant bird species with a gape large enough to consume the fruits of C. laevigatus.Template:Sfn

A 1966 article from the Ornithological Society of New Zealand documented a New Zealand bellbird (Anthornis melanura) feeding on the sap from the bark of C. laevigatus.Template:Sfn Other smaller New Zealand birds, such as the North Island robin (Petroica longipes), silvereye (Zosterops lateralis) and whiteheads (Mohoua albicilla) are known to search around C. laevigatus specimens for insects.Template:Sfn The endocarp of C. laevigatus are occasionally nibbled by Polynesian rat (Rattus exulans), while the larger brown rats (Rattus norvegicus) occasionally chew through the endocarps. Both species consume the flesh of C. laevigatus.Template:Sfn Possums (an invasive species in New Zealand) are also known to consume the ripe flesh of C. laevigatus fruits.Template:Sfn The extinct moa and other large birds likely consumed the fruits of C. laevigatus centuries ago.Template:Sfn C. laevigatus is a host species to the endemic New Zealand beetle Oemona hirta.Template:Sfn C. laevigatus is one of New Zealand's least flammable tree species with the highest moisture contents and the lowest flammability rates, as examined in a 2016 study.Template:Sfn

Relationship with humans

Cultivation

Corynocarpus laevigatus is common in cultivation and widely available for sale both in New Zealand and elsewhere in the world.Template:Sfn It was one of the most grown food crops by pre-European Māori (alongside kūmara and aruhe); they ate the drupe and seed after a long detoxification process.Template:SfnTemplate:Sfnm C. laevigatusTemplate:'s seeds contain a poisonous toxin (known as 'karakin') and other glucosides of 3-nitropropionic acid, which are highly toxic.Template:SfnTemplate:SfnTemplate:Sfn Some initial symptoms of poisoning include: diarrhoea, nausea and restlessness which develop to more severe gastrointestinal and neurological problems.Template:Sfn

Every autumn, pre-colonisation Māori would collect the seeds dropped from the coastal C. laevigatus trees. The seeds would be placed in open-weave traditional baskets (), washed in water to remove the outer pulp and baked and sun dried, a process that would remove toxicity from the seeds.Template:SfnmTemplate:Sfn

In Māori culture

A wooden plank displaying an artistic carving of a human-like figure, representing an ancestor of the Moriori people.

A Moriori tree carving () in the Canterbury Museum

Corynocarpus laevigatus is of great importance to Māori, who primarily used it as a food source.Template:SfnTemplate:Sfn In Māori mythology, C. laevigatus is told to be from Hawaiki, an ancestral homeland for the Māori people.Template:SfnTemplate:Sfn While pre-European Māori primarily valued C. laevigatus for its nutrition rather than medicine, they did use leaf undersides to draw out infections and fresh upper surfaces to heal injured skin.Template:Sfn

The seeds of C. laevigatus were of great value to Māori and needed to be prepared before they could be safely consumed, while the flesh of the fruits was consumed uncooked. The seeds are very poisonous and bitter in taste which had to be steamed properly in earth ovens ().Template:SfnmTemplate:Sfnm C. laevigatusTemplate:'s timber was also used in constructing canoes ().Template:Sfn

In Moriori culture

On the Chatham Islands, C. laevigatus have played a distinguished role in the history of the indigenous Moriori peoples; the bark of the C. laevigatus trees has been notably used for carving dendroglyphs rather than a food source.Template:Sfn A 2000 Department of Conservation report documented 147 C. laevigatus specimens with dendroglyphs on the Chatham Islands, although not all carvings were confirmed as authentically Moriori.Template:SfnTemplate:Sfn C. laevigatus (or in Moriori) is considered a (cultural treasure) amongst the Māori and Moriori peoples. Moriori also utilised C. laevigatus trees by carving on them; known as in the Moriori language, the carvings typically depict Moriori ancestors and are considered internationally significant and unique to their culture. A protects the remaining carved trees due to their fragile state, with conservation measures underway. C. laevigatus timber was also utilised by the Moriori to smoke and preserve food.Template:SfnTemplate:Sfn

Poisonings

Corynocarpus laevigatus has been linked to dog poisonings in New Zealand, leading to calls for the plant to be removed from urban areas.Template:SfnTemplate:Sfn

Recognition

An exoplanet originally named HD 137388 was renamed to "Karaka" in 2019 in honour of the tree's orange fruit.Template:Sfn A small community Template:Convert west of Whanganui named Pākaraka is also named in honour of the tree and its name reflects the "abundance of karaka trees" that previously were situated there.Template:Sfn New Zealand Post recognised C. laevigatus in 1967 by featuring it on penny postage stamps.Template:Sfn

See also

• List of trees native to New Zealand

Works cited

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External links

• Template:Commons category-inline