Written by Jacqui Lough (Lincoln University)
Edited by Michael Hudson, Lincoln University, May 2006
- Scientific name: Cordyline australis (G. Forst.)
- Synonym: Dracaena australis
- Popular common names: Cabbage tree, Ti kouka, lily palm.
- Other common names: Kiokio, Torquay palm, giant dragon tree.
- Kingdom: Plantae
- Phylum: Spermatophyta(seed plants)
- Class: Angiospermae(flowering plants)
- Order: Asparagales
- New Zealand Status: native (endemic)
- Taxonomy sources:Simpson (2000), Arkins (2003).
Cordyline australis is an iconic native with large strap-shaped leaves clustered into clumps with fragrant tufts (panicles) of white spring flowers (Harris, 2002). They can have multiple or single trunks with rough, corky bark. Cabbage trees are monocots (similar to grasses) with long, narrow, longitudinally veined leaves, typically 50 -100 cm long and 4–9 cm wide. On juveniles, drooping dead leaves hang down to form a skirt around the trunk. Old trees can reach 20 metres, with 1.5 metre diameter trunks bearing many branches (Harris, 2003).
Of about 20 species of Cordyline, five are native to New Zealand. These similar, but smaller, native species have distinguishing factors. The mountain cabbage tree (Cordyline indivisa) grows up to 5m tall with wide light-green leaves and is found in higher altitude forests. The forest cabbage tree Cordyline banksii (fig.3) grows to 4 metres high and has long petioles.
The Three Kings Island cabbage tree Cordyline kaspar, occurring naturally only on Three Kings Island, reaches 4m high and often branches near the ground (Arkins, 2003).
Full natural and naturalised range
The cabbage tree is present naturally only in New Zealand. The only other part of the world where they have been confirmed as becoming naturalised is Salt Point State Park in Northern California where it is listed as a "wild land weed of secondary importance" (Simpson, 2000).
New Zealand range
The Cabbage tree has a wide distribution across New Zealand, with the exception of southwest Fiordland. It has also been naturalised on Stewart Island and the Chatham Islands, probably introduced by Maori (Harris, 2002).
Naturally growing cabbage trees in Canterbury are found from Banks Peninsula to the foothills of the Southern Alps. Cabbage trees are far less abundant on the plains than before human settlement. Many cabbage trees that survived grazing and crop cultivation are isolated in paddocks and are in slow decline (Simpson, 2000). Natural cabbage tree habitats are now fragmented with large gaps in their distribution. This separation has affected the appearance of trees, probably due to the development of genetic differences between isolated populations (Harris, 2003).
Natural History in Canterbury
In primeval New Zealand cabbage trees occupied a range of habitats; anywhere open, moist, fertile and warm enough for them to establish and mature. Usually in lowland swamps, lake and river margins, forest clearings and isolated rocky outcrops. In 1843 Ernst Dieffenbach described ‘riparian jungles of cabbage trees’.
Today cabbage trees in Canterbury exist in relatively few places where they can be said to be growing in their natural environment. The flood plains and drained wetlands of Canterbury have been largely cultivated and inhabited by people. Now they are found in gardens, landscape plantings, farm shelterbelts, regenerating gullies and isolated in grazed paddocks (Simpson, 2000).
Cabbage trees need open space for seedling establishment without shading by overtopping vegetation. These open habitats can be created by flooding, wind, snow, frost and volcanic activity. They do not thrive in salty or acidic soils and seedlings are vulnerable to frosty or dry conditions (Simpson, 2000).
A cabbage tree year can be regarded as beginning in late autumn. Formed throughout the spring, summer and early autumn a tight spike of unopened leaves project from each tuft. Some shoots grow into miniature future flowers. These young inflorescences spend the winter protected by the spikes of unopened leaves (Simpson, 2000).
In spring the flowers open sequentially from the base of the inflorescence to the tip. Each flower stalk arises from the centre of the tuft of leaves and carries hundreds of tiny creamy-white flowers producing copious amounts of sweet-smelling nectar. The flower stalks are very strong to withstand wind and the weight of birds. As insects gather nectar they transfer pollen between flowers on their bodies. Many different insects are attracted to the cabbage tree flowers – moths, bees, and flies and wasps. Flowering occurs for four to six weeks (Arkins, 2003) and is heavier every second year (Harris, 2001).
After flowering the tiny inflorescences develop thousands of fruits (Simpson, 2000) in the form of round berries. At about 4 to 5 millimetres in diameters the berries change from green to a creamy colour. The fruit attract many important, seed-dispersing, native birds such as the Tui (Prosthermadera novaeseelandiae), wood pigeon (Hemiphaga novaeseelandiae) and bellbird (Anthornis melanura), now joined by the blackbird (Turdus merula), starling (Sturnus vulgaris) and sparrow (Passer domesticus). They digest the fleshy part of the fruit. Each fruit contains 3 to 6 seeds with a black, shiny, protective coating called phytomelan that allows it to survive passage through the gut of the bird (Arkins, 2003).
Cabbage tree seeds contain stores of linoleic acid that nourish the embryo and developing seedling. This means the seed can remain alive in the soil for a number of years before germinating. Once germinated, seedlings need full sunlight to grow well (Arkins, 2003).
If conditions are right, young trees can grow to 1 metre high in 2 to 3 years. The juvenile phase (before flowering) lasts five to ten years. The leaves of juveniles differ from those of adults, with toothed margins and a narrower base. Cabbage tree leaves usually fall off after two years, but on juveniles the dead leaves hang down, creating a skirt around the tree that protects it from drought, frost and animal damage (Harris, 2004). The juvenile tree grows upwards without branching (fig.5) until it reaches several metres in height with a trunk 5 to 10 cm in diameter. Below ground, a bud in the axel of one of the earliest leaves of the seedling forms a second stem which grows vertically down into the soil. This rhizome increases the opportunity for new roots to form, helps to anchor the plant and stores food and water (Simpson, 2000).
Flowering induces branching and the height of the trunk at first flowering establishes the height from which future branches arise. The young adult cabbage tree will form 2 or 3 new branches that grow for several years before themselves flowering and branching again. Usually each branch grows at the same rate, creating a symmetrical canopy. As the canopy rises and expands, some branches die and fall off, others flower more slowly and the canopy becomes asymmetrical. The number of leaves in each tuft decreases with age. The root system in cabbage trees helps them adapt to different environments; a young adult cabbage tree has thousands of roots (Simpson, 2000).
As the tree matures, epicormic branches can grow from buds that lie dormant in the trunk and branches. Following injury, such as losing as branch, a new bud grows out from below the point of injury (fig.5). This ability to produce new shoots from the trunk means cabbage trees can regenerate after severe storms or fire, even if the rest of the tree is lost (Arkins, 2003).
From spring to autumn each year, the branches and trunk thicken forming a new layer of wood around the trunk. New roots grow horizontally into the soil; some die and are replaced. Cabbage trees can reach their maximum height (10 to 15 metres) in 20 years. Subsequent growth consists of replacing branches in the canopy (Simpson, 2000).
Cabbage trees age dramatically. Noticeable by the splitting of the trunk, a mature tree is always hollow. Stresses caused by wood-rotting fungi, insects and water and wind can cause parts of the tree to fall off and the trunk to divide into portions. It is a slow process because new epicormic shoots can replace whole sections of the canopy. Eventually the trunk will fall. However, this is not the end; the bark of an old tree may be covered in many rhizomes. After the tree falls the rhizomes can grow into new stems called epirhizic shoots. These new shoots are like juvenile cabbage trees with sharply toothed leaves and a skirt of dead leaves around the base. This means that a grove of cabbage trees could be a thousand years old (Simpson, 2000).
100+ years (Simpson, 2000).
Many pests and diseases affect cabbage trees. The larvae of the cabbage tree moth (Epiphryne verriculata) eat holes in the unopened leaves. When the leaves open the cabbage tree can appear severely damaged with some leaves splitting off in the wind. Another moth living on cabbage trees is Catamacta lotinana, whose larvae bore into the fleshy stem forming cavities. In preparation of the pupal stage C. lotinana draw the margin of a leaf together with silk and pupate inside. After they leave, the leaf appears shredded (Simpson, 2000). A native cabbage tree scale insect (Leucapsis cordylinidis) covers the undersides of leaves and sucks the sap. The result is the eventual killing of the heads of the leaves. The native wood tunnelling beetle (Platypus apicalis) kills the leaves and eventually the tree.
Trees along the Kaikoura coast often have the fungi Sphaeropsis cordyline, causing leaf spots. Additionally the fungi Phanerochaete cordylines attacks decaying wood, spreading into the tissue of the tree and killing it (Simpson, 2000).
Cabbage trees are often the only trees in a paddock. Farm animals use them for shelter, food and for scratching themselves on. This can prevent new growth and erode the soil, restricting new root growth. These combined effects have caused a slow ‘rural decline’.
Since the late 1980s, widespread death of cabbage trees has occurred through much of the North Island and parts of the South Island. Over a period of months, the leaves of healthy cabbage trees became yellow and fell off with trees finally dying. The cause of this ‘sudden decline’ is a thought to be a biotic disease caused by a parasite spreading a type of bacterium called a phytoplasma from dead and dying trees (Beever et al., 1996).
Cabbage trees are smothered and suffocated by old mans beard (Clematis vitalba) and ivy (Hedera helix). Unable to survive in the shade of pine forests cabbage trees also do not regenerate in dense gorse (Arkins, 2003).
Cabbage trees provide habitat for many plants and animals. Unique characteristics allow coexistence with many introduced species and cabbage trees can often be found growing with willows along riverbanks. Many climbing plants, mosses, lichens and fungi have taken advantage of their rough bark (Arkins, 2003).
How to find a Cabbage Tree
Cabbage trees are easily recognisable in their habitat by their distinct form and are clearly visible in the open or along bush or riparian margins.
Abundance and Conservation Status
- New Zealand: abundant
- Canterbury: abundant
Loss of habitat, including wetlands, is one of the biggest threats to the cabbage trees, together with grazing and damage of trees on farmland by agricultural animals. Remaining natural environments need protection to ensure regeneration can occur (Arkins, 2003).
Significance for people
Traditional Maori significance and uses
Cabbage trees are considered to be footprints in the Maori landscape, marking trails, camping places, river crossings, settlements and burial grounds. Traditionally Maori harvested parts of the cabbage trees for food and medicine, and used the leaves for making sandals, cloaks and mats (Arkins, 2003).
Early settlers used cabbage trees for stockyards by stringing flax rope around a grove of the trees. Trunks were used for building and the leaves for thatched roofs. They were used for place names (‘Cabbage Tree Flat’) and even for making rum (Simpson, 2000).
Cabbage trees often feature in gardens and urban plantings. Cabbage trees are also being used on farms in shelterbelts (personal observation). They appear in artworks for their unique features and symbolism. They are distinctive symbols of the New Zealand landscape (Simpson, 2000).
The cabbage tree is a recognisable and symbolic feature throughout most of New Zealand due to its characteristic form and cultural history. Although abundant, its conservation cannot be ignored and its natural habitats need to be restored in order for it to regenerate into the future.
Arkins, A. (2003). The Cabbage Tree. Auckland. Reed publishing.
Beever, R. E., Forster, R. E., Rees-George, J., Robertson, G. I., Wood, G.A. & Winks, C.J. (1996). Sudden Decline of the Cabbage Tree (Cordyline australis): Search For The Cause. New Zealand Journal of Ecology, 20, 53–56.
Harris, W. (2001). Horticultural and conservation significance of the genetic variation of cabbage trees (Cordyline spp.). In: Oates, M. R. ed. New Zealand plants and their story: proceedings of a conference held in Wellington 1–3 October 1999. Lincoln, Royal New Zealand Institute of Horticulture. Pp. 87–91.
Harris, W. (2002). The cabbage tree. Journal of the Royal New Zealand Institute of Horticulture, 5, 3–9.
Harris, W. (2003). Genotypic variation of height growth and trunk diameter of Cordyline australis (Lomandraceae) grown at three locations in New Zealand. New Zealand Journal of Botany, 41, 637–652.
Harris, W. (2004). Genotypic variation of dead leaf retention by Cordyline australis (Lomandraceae) populations and influence on trunk surface. New Zealand Journal of Botany, 42, 833–844.
Simpson, P. (2000). Dancing Leaves: The story of the New Zealand cabbage tree: Ti Kouka. Christchurch. Canterbury University Press.