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July - Kohekohe - Native Plant of the Month

Dysoxylum spectabile

Lush, tropical-looking kohekohe leaves
A specimen of kohekohe collected by Banks and Solander in 1769 when the Endeavour first visited Aotearoa. This specimen is now held in Te Papa’s herbarium collection.
A specimen of kohekohe collected by Banks and Solander in 1769 when the Endeavour first visited Aotearoa. This specimen is now held in Te Papa’s herbarium collection. CC BY 4.0. Te Papa (SP063821_A)

Kohekohe are spectacular by name and nature, and July is one of the best months to appreciate them. They are both winter fruiting and flowering, making them extremely important sources of food for a range of different birds during this lean time of year.

Kohekohe was one of the very earliest specimens collected by botanists on board the Endeavour when Captain Cook first visited Aotearoa. This dried specimen is now held in Te Papa’s collection. The specimen includes a flower stem, meaning the men must have witnessed the trees in bloom, which would have been a striking contrast to the European plants that they were used to seeing at home. Despite early interest and use by both Maori and Pakeha, kohekohe are not currently as well known by the public as they might be. However, there is a good chance that most Aucklanders know a place that was once notable for kohekohe. The area now known as Pukekohe is an abbreviation of the name “puke kohekohe” which means hill of kohekohe.

A spray of kohekohe flowers
A spray of kohekohe flowers

Kohekohe are sometimes called the New Zealand mahogany because they are the only representatives of the mahogany plant family native to New Zealand. There was some early colonial excitement about the potential of this species for a timber industry. Seeds were collected and sent overseas to tropical countries, such as India, where it was thought that the climate would speed up growth and plantations could be managed. This enthusiasm was undone by kohekohe’s habit of often developing hollow trunks as trees mature. Maori used kohekohe timber to carve waka for river navigation and also used kohekohe leaves in medicines to treat a range of ailments.

The early colonial settlers took a different tack and attempted to use the leaves as a replacement for hops in beer brewing. The leaves have a strong bitter taste and so it is not surprising that this ingredient quickly disappeared from drinks.

Kohekohe flowers grow directly out of tree trunks and branches.
Kohekohe flowers grow directly out of tree trunks and branches.

Kohekohe’s tropical family traits extend beyond having lovely (if hollow) timber. They have very large, glossy leaves, which are frost-tender. This limits them to growing in warmer lowland forest habitats. Kohekohe also have very thin bark, which enables them to grow their flower stems directly out of their trunks and main branches - a flowering process called cauliflory. It has been suggested that sprouting flowers off the trunk in this way, well under the canopy, is an adaptation to encourage bird pollination. If it is, then it has worked! Kohekohe are very well adapted to both bird pollination and seed dispersal. Nectar-feeders like tūī, korimako/bellbirds, hihi and tauhou/silvereyes merrily visit the flowers, spreading pollen generously around. It is also possible that our native short-tailed bats were pollinators for kohekohe before mammalian predators limited their range so severely. Kohekohe flowers are white and green, star shaped and you could be forgiven for mistaking them for an exotic orchid. They bloom during winter and in a good flowering year their trunks look like they are draped in lace. Some people say that kohekohe flowers have a pleasant scent, which is described as “spicy and sweet”, but we have yet to smell this elusive perfume. If you do, please let us know your thoughts on it! Kohekohe fruit take almost a year to develop and ripen in late autumn and early winter, just before and during the beginning of the flowering season. The fruit grow straight out of the trunk and look similar to clusters of green figs. As they ripen the outer green case splits open to expose bright orange flesh inside surrounding seeds. As this interior is exposed the bolshy tūī appear, sharing the fruit feast reluctantly with kererū and kōkako.

Left: Kohekohe flowers, right: kohekohe with bunches of fruit

Kohekohe are hardy trees, and aside from their aversion to heavy frosts, they are happy growing in a wide range of conditions. They are common canopy trees in lowland forests throughout the upper third of the North Island, although they are far less common than they once were. This is because their lush leaves and attractive flowers and fruit are greatly enjoyed by possums. Rats also eat their fruit and seeds. The flowers and fruit are eaten with such enthusiasm that without pest control kohekohe are not able to reproduce. This means that there has been no replacement of older trees across large parts of the country. Luckily, with pest control, these trees bounce back and we are lucky enough to see not just the beautiful flowers and fruit, but also lots of lovely young seedlings growing up in areas with trapping in Kaipātiki.

 Kohekohe with sprays of flowers and flower buds
Kohekohe with sprays of flowers and flower buds

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