Tree spotlight no:7 – Cordyline Palm

cordyline-australis

Cordyline australis, commonly known as the cabbage tree, cabbage-palm is a widely branched monocot tree endemic to New Zealand. The genus name Cordylinem derives from an Ancient Greek word for a club (kordyle), a reference to the enlarged underground stems or rhizomes, while the species name australis is Latin for “southern”. The common name cabbage tree is attributed by some sources to early settlers having used the young leaves as a substitute for cabbage.

It grows up to 20 metres (66 feet) tall with a stout trunk and sword-like leaves, which are clustered at the tips of the branches and can be up to 1 metre (3.3 feet) long. With its tall, straight trunk and dense, rounded heads, C. Australis is a characteristic feature of the New Zealand landscape. Its fruit is a favourite food source for the New Zealand pigeon and other native birds.

native-nz-cabbage-trees-cordyline-australis-timarusouth-canterburysouth

It grows in a broad range of habitats, including forest margins, river banks and open places, and is abundant near swamps. The largest known tree with a single trunk is growing at Pakawau, Golden Bay. It is estimated to be 400 or 500 years old, and stands 17 metres (56 feet) tall with a circumference of 9 metres (30 feet) at the base. Known to Māori as tī kōuka, the tree was used as a source of food, particularly in the South Island, where it was cultivated in areas where other crops would not grow. It provided durable fibre for textiles, anchor ropes, fishing lines, baskets, waterproof rain capes and cloaks, and sandals.

Hardy and fast growing, C. Australis is widely planted in New Zealand gardens, parks and streets, and numerous cultivars are available. The tree can also be found in large numbers in island restoration projects such as Tiritiri Matangi Island, where it was among the first seedling trees to be planted.

It is also grown as an ornamental tree in Northern Hemisphere countries with mild maritime climates, including parts of the upper West Coast of the United States and the warmer parts of the British Isles, where its common names include Torbay palm, and Torquay palm. It does not do well in hot tropical climates like Queensland, Southeast Asia and Florida.

Magnified view of flowers of C. australis. Each flower has a style tipped by a short trifid stigma. There are also anthers with pollen, and nectar around the base of the ovary. In a good flowering season, a large tree may produce 1 million seeds. Before it flowers, it has a slender unbranched stem. The first flowers typically appear at 6 to 10 years old, in spring. After the first flowering, it divides to form a much-branched crown with tufts of leaves at the tips of the branches. Each branch may fork after producing a flowering stem. The pale to dark grey bark is corky, persistent and fissured, and feels spongy to the touch.

The long narrow leaves are sword-shaped, erect, dark to light green, 40 to 100 cm (16 to 39 in) long and 3 to 7 cm (1.2 to 2.8 in) wide at the base, with numerous parallel veins. The leaves grow in crowded clusters at the ends of the branches, and may droop slightly at the tips and bend down from the bases when old. They are thick and have an indistinct midrib. The fine nerves are more or less equal and parallel. The upper and lower leaf surfaces are similar.

Large, peg-like rhizomes, covered with soft, purplish bark, up to 3 metres (9.8 feet) long in old plants, grow vertically down beneath the ground. They serve to anchor the plant and to store fructose in the form of fructan. When young, the rhizomes are mostly fleshy and are made up of thin-walled storage cells. They grow from a layer called the secondary thickening meristem.

Response to fire

Cordyline australis is one of the few New Zealand forest trees that can recover from fire. It can renew its trunk from buds on the protected rhizomes under the ground. This gives the tree an advantage because it can regenerate itself quickly and the fire has eliminated competing plants. Cabbage tree leaves contain oils which make them burn readily. The same oils may also slow down the decay of fallen leaves, so that they build up a dense mat that prevents the seeds of other plants from germinating. When the leaves do break down, they form a fertile soil around the tree. Cabbage tree seed also has a store of oil, which means it remains viable for several years. When a bushfire has cleared the land of vegetation, cabbage tree seeds germinate in great numbers to make the most of the light and space opened up by the flames.

Insect habitation:

Insects, including beetles, moths, wasps and flies, use the bark, leaves and flowers of the tree in various ways. Some feed or hide camouflaged in the skirt of dead leaves, a favorite dry place for weta to hide in winter. Many of the insect companions of C. Australis have followed it into the domesticated surroundings of parks and home gardens. If the leaves are left to decay, the soil underneath cabbage trees becomes a black humus that supports a rich array of amphipods, earthworms and millipedes.

There are nine species of insect only found on C.australis, of which the best known is Epiphryne verriculata, the cabbage tree moth, which is perfectly adapted to hide on a dead leaf. Its caterpillars eat large holes and wedges in the 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 young trees but seldom damage older trees, which lack the skirt of dead leaves where the parent moths like to hide.

The Cordyline Palm and the Māori:

The tree was well known to Māori before its scientific discovery. The generic Māori language term for plants in the Cordylinegenus is tī, and names recorded as specific to C. Australis include tī kōuka, tī kāuka, tī rākau, tī awe, tī pua, and tī whanake. Each tribe had names for the tree depending on its local uses and characteristics. Simpson reports that the names highlight the characteristics of the tree that were important to Māori. These include what the plant looked like—whether it was a large tree (tī rākau, tī pua), the whiteness of its flowers (tī puatea), whether its leaves were broad (tī wharanui), twisted along the edges (tī tahanui), or spiky (tī tarariki). Other names refer to its uses—whether its fruit attracted birds (tī manu), or the leaves were particularly suitable for making ropes (tī whanake) and nets (tī kupenga). The most widely used name, tī kōuka, refers to the use of the leaf hearts as food.

cordyline_berries

The berries of C. Australis are enjoyed by bellbirds, tūī and pigeons. Māori sometimes planted groves of cabbage trees (pā tī) to attract pigeons which could be snared when they came to eat the berries.

Food

The stems and fleshy rhizomes of C.australis are high in natural sugars and were steam-cooked in earth ovens (umu tī, a large type of hāngi) to produce kāuru, a carbohydrate-rich food used to sweeten other foods. The growing tips or leaf hearts were stripped of leaves and eaten raw or cooked as a vegetable, when they were called kōuka—the origin of the Māori name of the tree.

Preparation of a modern hangi for tourists at Mitai Maori Village, Rotorua

The kōata, the growing tip of the plant, was eaten raw as medicine. When cooked, it was called the kōuka. If the spike of unopened leaves and a few outer leaves is gripped firmly at the base and bent, it will snap off. The leaves can be removed, and what remains is like a small artichoke heart that can be steamed, roasted or boiled to make kōuka, a bitter vegetable available at any time of the year. Kōuka is delicious as a relish with fatty foods like eel, mutton birds, or pigeons, or in modern times, pork, mutton and beef. Different trees were selected for their degree of bitterness, which should be strong for medicinal use, but less so when used as a vegetable.

palm as fibre plant for weaving

Fibre

A tough fibre was extracted from the leaves of C.australis, and was valued for its strength and durability especially in seawater. The leaves were used for making anchor ropes and fishing lines, cooking mats, baskets, sandals and leggings for protection when travelling in the South Island high country, home of the prickly spear grasses (Aciphylla) and tūmatakuru or matagouri (Discaria toumatou). Morere swings provided a source of amusement for Māori children. The ropes had to be strong, so they were often made from the leaves or fibre of C.australis, which were much tougher than the fibers of New Zealand flax. The leaves were also used for rain capes, although the mountain cabbage tree C.indivisa, was preferred. The fiber made from cabbage tree leaves is stronger than that made from New Zealand flax.

ti_kouka_sandals,jpg

Medicine

The Māori used various parts of Cordyline australis to treat injuries and illnesses, either boiled up into a drink or pounded into a paste. The kōata, the growing tip of the plant, was eaten raw as a blood tonic or cleanser. Juice from the leaves was used for cuts, cracks and sores. An infusion of the leaves was taken internally for diarrhea and used externally for bathing cuts. The leaves were rubbed until soft and applied either directly or as an ointment to cuts, skin cracks and cracked or sore hands. The young shoot was eaten by nursing mothers and given to children for colic. The liquid from boiled shoots was taken for other stomach pains. The seeds of Cordyline australis are high in linoleic acid, one of the essential fatty acids.

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