Cabbage Tree

Cabbage trees of Tangihua Ranges Northland

Cabbage trees are an important source of food for insects, birds and people

The Cabbage Tree was given its common name during early European voyages of discovery in the 18th century. The trees looked like the palm trees European’s found elsewhere, all of which were known as Cabbage Trees as the growing point in the centre of the leaves could be cooked and eaten like a cabbage. Europeans also worked out how to utilise the plant to make alcohol and the often fearsome brews were relished by whalers and sealers.

New Zealand has five species of Cabbage Tree

The first three in the list can be found in the Tangihua forest;

Latin Name / Maori Name / Common Name

Although included in the list, Tī Koraha or the Dwarf Cabbage Tree is not technically a tree as it has no trunk or branches. Some plants very similar to Tī Koraha have been found with short trunks, but these may be hybrids of Tī Koraha and either Tī Kōuka or Tī Ngahere.

There was another species of Cabbage Tree, Cordyline fructicosa, brought to New Zealand from the Pacific Islands by Māori who used it as a source of food. It was unable to germinate on its own in New Zealand so only survived in the far North where it was cultivated by Māori. The introduction of European food meant it was no longer needed and so disappeared.

Cabbage Trees are not unique to New Zealand. Other species of Cabbage Trees are native to Australia, New Caledonia, New Guinea, and places as far away as Brazil and Mascarene near Madagascar

Hybrid Cabbage Trees

Cabbage tree hybridization is important for genetic diversity. It allows for different variations of the plant which can adapt to diverse or a changing environments

Cabbage Trees interbreed, creating hybrids. Tī Ngahere readily hybridises with Tī Kōuka and Tī Koraha. A Tī Koraha and Tī Ngahere hybrid is known as Cordyline x matthewsii. There may well be examples of these in the Tangihua ranges.

Cabbage trees in the Tangihua forest

The three species of Cabbage Tree found in Northland Tangihua forest are;

• Cordyline Australis – Ti kouka The most common one seen outside the forest
• Cordyline Banksii – Tī ngahere Forest Cabbage Tree
• Cordyline Pumilio – Ti koraha Dwarf Cabbage tree, has no stem

All three can be found on The Nature Trail, often all in the same place as seen below

CB – Cordyline Banksii , Tī ngahere , CA – Cordyline Australis, Ti kouka, CP – Cordyline Pumilio, Ti koraha

How to pick the difference between our cabbage trees

Physical Description

The Root

At an early age a branch of the Cabbage Tree will grow vertically downwards, like a tap- root, to anchor the plant. This root, or rhizome grows large and is used by the plant to store reserves of sugar and water. The rhizome also contains thousands of buds that can grow into new Cabbage Trees.

The Branches

The branches of Cabbage Trees differ greatly between the species and even between trees of the same species. The only similarity is that each branch ends with an inflorescence, a connected bunch of flowers.

The Leaves

When not in flower it is the leaves of the Cabbage Trees that are their most prominent feature. The leaves of all the species of Cabbage Trees are long, thin and tough. The exact shape of the leaves can be used to differentiate one species of Cabbage Tree from the others. See section above on how to spot the difference between the Cabbage Trees in the Tangihua Ranges.

The Flowers

The first flowers typically appear when the Cabbage Tree is between six and ten years old.

During the autumn months some of the growing tips at the end of the branches start producing inflorescences. Around the outside of the inflorescences the plant develops leaves and these unopened leaves give the inflorescences protection to grow over winter months.

The trees flower for four to six weeks in spring or early summer. When Cabbage Trees flower early it is considered an indication of a drought but is often only an indicator of a dry spring.

When Cabbage Trees are flowering they can be found by using your nose or ears. They produce a sweet perfume that can be quite strong, particularly if there are lots of flowers or lots of trees, and the perfume attracts bees that can be heard buzzing through the flowers.

The Fruit

It takes about two months for the fruit to ripen. By the end of summer a Cabbage Tree can have thousands of small fruits available for birds to eat and disperse.

Each fruit contains three to six shiny, black seeds which are coated in a charcoal-like substance called phytomelan. This substance may serve to protect the seeds from the digestive process while in the guts of birds.

Cabbage trees tend to flower heavily in alternative years, with a bumper crop of flowers every three to five years. On average an inflorescence bears 5,000 to 10,000 flowers, so a large inflorescence may contain up to 40,000 seeds, one million seeds per tree, or hundreds of millions for each healthy grove of Cabbage Trees.

Photos of cabbage trees

Forest Role

The Cabbage Tree plays a very important role in the forest as a source of food and a habitat for a wide range of birds, plants and insects.

Flowers

Cabbage Tree flowers provide nectar for bees, birds, geckos and other insects. The trees benefit from their visitors as they transfer pollen, fertilising the flowers. The flowers attract the insects and bees by producing a sweet perfume and the nectar contains aromatic compounds, mainly esters and terpenes, which are particularly attractive to moths. Bees use the nectar to produce a light honey to feed their young and increase the size of the hive in the early summer.

Lizards and other insects forage amongst the flowers. These include the Gold-Striped Gecko which is well camouflaged for life among the leaves of the Cabbage Trees. The lizards and insects on the Cabbage Trees in turn become food for birds such as Saddlebacks.

Fruit

The white berries are a good food for the Cabbage Tree Moth and birds such as Kererū. The seeds inside the berries are rich in linoleic acid, a food source for the developing embryo plant and a compound that is important in the egg-laying cycle of birds.

Leaves

The Cabbage Tree Moth and its caterpillar utilise the Cabbage Tree leaves for food and habitat. The moth hides under the old leaves during the day before emerging at nightand the caterpillars feed on the young leaves until they turn into moths.

The old, dead leaves and flower stalks provide great places for birds to nest under and Moreporks and Kingfishers will make holes in the old trunks to build their nests.

Branches

Long Tailed Bats can find shelter for the day in the hollow branches of Cabbage Trees.

Other Plants

Epiphytes will grow on larger Cabbage Trees along with mosses, liverworts, lichens and fungi. Two species of fungi; Phanaerochaeta cordylines and Sphaeropsis cordylines, occur almost exclusively on Tī Kōuka.

Unique to the Cabbage Tree

There are nine species of insect found only on Cabbage Trees. The best known is the Cabbage Tree Moth, which is perfectly adapted to hide on the dead leaves. The moth lays its eggs at the base of the central spike of unopened leaves. The caterpillars eat holes in the surface of the leaves and leave characteristic notches in the leaf margins. They can infest and harm young trees but seldom damage older trees, which lack the skirt of dead leaves where the moths like to hide

Regeneration

This Cabbage Tree was cut down at the Tangihua confidence course and the rhizome has sprouted three more branches or stems

Cabbage Trees are good colonising species, growing happily after a fire, on bare ground or in exposed places.

Cabbage Tree seeds contain a store of oil allowing them to remain viable in the ground for several years. This makes them a great species for regeneration as when the land is cleared, either by nature or humans, there are lots of Cabbage Tree seeds ready to germinate and make the most of the light and open space.

Although a ‘tree’ will only live for around 100 years, the plant itself can survive much longer. The large tap root or rhizome contains thousands of buds, each capable of becoming a new trunk. If the original ‘tree’ is destroyed by fire or rot, these new buds will grow, often forming a circle around the old damaged or destroyed trunk. A great example of this can be found next to the Confidence Course in the Tangihua forest.

Cabbage Tree branches will sprout from cuts made in the bark and fallen trees have been known to regenerate by sprouting branches and roots. This allows the Cabbage Tree to regenerate itself quickly after a fire, big storm or slip.

Cabbage Tree leaves contain oils which make them burn readily. These same oils may also slow down the decay of fallen leaves so that they build up a dense mat around the base. This protects the Cabbage Tree from competition by preventing the seeds of other plants from germinating to close.

Cabbage tree seed also has a store of oil, which means it remains viable for several years. This means when a bushfire has cleared the land of vegetation, there are lots of cabbage tree seeds ready to germinate and make the most of the light and space opened up by the flames.

Distribution and Habitat

Cabbage Trees arrived in New Zealand around 15 million years ago. This has given them plenty of time to adapt to the different regions in New Zealand.

Cordyline australis, Tī Kōuka, Common Cabbage Tree

Tī Kōuka is the tallest of New Zealand’s Cabbage Trees is found in lowland and lower mountain forests throughout New Zealand. It favours moist soils and open spaces so is often found near the edges of lakes and swamps or on slopes nears springs and other water sources.

Cordyline banksia, Tī Ngahere, Forest Cabbage Tree

Tī Ngahere can be found throughout the North Island and in the South Island down to Otago and south Westland. This species is typically found in open places in coastal to lowland forest but can extend into the moist lower mountain forests.

Cordyline pumilio, Tī Koraha: Dwarf Cabbage Tree

Tī Koraha is found in light lowland forest and shrubland as far south as the Bay of Plenty. It is often found in Kauri forests, like the Tangihua forest, and scrub land where kauri gum digging occurred.

Cordyline obtecta

C. obtecta is found on the Three Kings Island to the north of New Zealand, Murimotu Island off North Cape, on the Poor Knights Islands and in one small area of North Cape. It is the same species as those found on Norfolk Island.

Cordyline indivisa, Tōī, Mountain Cabbage Tree

Toī is another Cabbage Tree that prefers open spaces. It is found from Great Barrier Island and the Coromandel Peninsula to the bottom of the South Island. In most areas it is found in mid to high altitude areas, but it can become coastal in the far south.

Cabbage tree sudden decline syndrome

In 1987 cabbage trees in Northland started to die off in significant numbers. In some areas no big treeswere left. As this plague spread it was referred to as sudden decline syndrome. A bacteria called phytoplasma australiense was found to be the cause .The passion vine hopper introduced from Australia spread this bacteria which is native to New Zealand flax.

It is a case where an introduced species allowed a disease to cross from one species to another.

Plants stricken with this illness suddenly and rapidly wilt, with leaves falling off still green. Infected trees usually die within 3 to 12 months. The good news is that although sudden decline often affects cabbage trees in farmland and open areas, trees in natural forest patches continue to do well.

There is no known cure except to ensure as many cabbage trees are planted as possible

Variations and Hybrids of Tī Kōuka

Hybridization is important for genetic diversity. It allows for different variations of a plant which can adapt to diverse or a changing environment.

Throughout New Zealand

Although this Tī Kōuka is found throughout New Zealand it varies in appearance from place to place.

Variations in the overall appearance of the tree, canopy shape, branch length and size are often due to the space available, with bushier trees in the open and straighter, less branched trees in crowded areas.

Tī Kōuka has also been found to vary between regions. A study of Tī Kōuka seedlings grown from seeds collected in 28 different areas found that the further south the trees, the longer and narrower the leaves. Seedlings often have leaves with red-brown pigmentation which disappears in older plants and this colouration becomes increasingly common further south. These changes, which also seem to be dependent on altitude, suggest the Cabbage Tree has learnt to adapt to the colder weather found in southern regions and at higher altitudes.

In Northland

Tī Kōuka shows a great deal of genetic diversity in Northland, suggesting older genetic lines of the species have been able to endure in Northland and not elsewhere in the country.

In the Far North, some Tī Kōuka have floppy, narrow leaves, rather than wide, stiff leaves like most Tī Kōuka. This may be due to some form of hybridisation with Tī Koraha, the Dwarf Cabbage Tree, which has much narrower leaves.

In eastern Northland most Tī Kōuka have straight, dark green leaves but some trees have been found with much broader leaves than normal. These may be a hybrid with C. obtecta. Other, similar C. obtecta characteristics appear in populations of Tī Kōuka along parts of the eastern coastline from the Karikari Peninsula in the Far North to the Coromandel Peninsula.

In western Northland and Auckland there is another form of Tī Kōuka, often called Tītī, which can often be found growing in young Kaui forests. When young, Tītī are generally very spindly but when growing in the open they can become massive trees with numerous long, thin branches and relatively short, broad leaves.

Author Rachael Mannion

References

It is very apparent that specific information has been shared online between many organisations. Attributing to the initial source is impossible. As much as possible we have used our own photo’s and the following websites have been used as sources for our information

• Te Ara The Encyclopaedia of New Zealand
• Wikipedia
• DOC website.
• T.E.R:R.A.I.N Taranaki Educational Resource: Research Analysis and Information Network