Cordyline australis, commonly known as the cabbage tree or Tī Kōuka is endemic to New Zealand. Generally a lowland species, it grows from sea level to about 1,000 ASL including in the foothills of the Southern Alps, where deforestation may have played a part in giving it room to grow. Cabbage trees remain a common and thriving species within much of the more highly modified ecosystems of coastal and lowland New Zealand. It grows in a broad range of habitats, including forest margins, river banks and open places, and is most commonly encountered on alluvial terraces within riparian forest.
Cordyline australis is a light-demanding pioneer species, and seedlings die when overtopped by other trees. To grow well, young plants require open space so they are not shaded out by other vegetation. Although adult trees can store water and are drought resistant, seedlings need a good supply of water to survive. Tī Kōuka are a favourite of livestock and browsing pests, so fencing or guards is often necessary at the seedling stage.
Tī Kōuka grows up to 20 metres 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 long. Many plants and animals are associated with Cordyline australis in healthy ecosystems. The most common epiphytes are ferns, astelias and orchids. Its fruit and nectar are a favourite food source for kererū and tūī. Bellbirds like to nest in Tī Kōuka. Some lizards forage among the flowers of Cordyline australis and the nectar of the flowers is sought after by insects. The leaves and the rough bark provide excellent homes for insects such as caterpillars and moths, small beetles, fly larvae, wētā, snails and slugs. If the leaves are left to decay, the soil underneath cabbage trees becomes black humus that supports a rich array of amphipods, earthworms and millipedes.
In spring and early summer (September to January), sweetly perfumed white flowers are produced in large, dense flower spikes 60 to 100 cm long, bearing well-spaced to somewhat crowded flowers. Good flowering seasons occur every few years only and tend to follow dry seasons. Flowers are followed by fleshy berries from December to March which are dispersed by frugivory.
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. For more information about Māori plant use, see Landcare Research’s listing here.