November in the hills with Chris Horne and Barbara Mitcalfe
Cordyline australis, cabbage tree, tī kōuka
Many early New Zealand paintings featured this iconic tree species, tī kōuka, a long-lived NZ endemic in the Asparagaceae family, all members of which are monocots (short for monocotyledons). This means that their first shoots appearing above the ground are single, as you may have noticed with other monocot plants such as grasses, lilies, orchids and palms.
Palms used to be known as 'cabbage trees' because their leaf tips could be eaten. During the 18th-_century voyages when Europeans discovered Aotearoa, it was noted that our Cordyline australis trees resembled palm trees, so explorers called them 'cabbage trees' and that name has stuck.
Tī kōuka can grow to 20 m tall. You see them in the North, South and Stewart islands, from sea level to 600 m altitude. They are often the only survivors in open spaces, because the surrounding bush has disappeared, or in swamps, which have not been drained. The trunks of old tī kōuka may be 2 m in diameter, and so durable that early settlers sometimes hollowed them out to use as chimneys. It is recorded that these often lasted longer than the huts themselves, and when the owners departed, they sprouted, starting a another long life.
Tī kōuka have many branches, and thick, rough, fissured bark. The tough, light-green leaves, crowded towards the end of the branches, are up to 1 m long and 6 cm wide. The large inflorescences, comprising hundreds of flowers, are 0.60-1.5 m by 30-60 cm and much-branched. The white, sweet-scented flowers appear in spring and produce whitish fruit c. 4 mm in diameter containing several black seeds. Their seedlings may appear in abundance in your garden because birds feed on the fruit.
Māori used tī kōuka leaves for cordage and weaving. In Fishing methods and devices of the Māori, Elsdon Best records that in 1885, a giant seine net (kupenga) 2090 yards (over 1.9 km) long was made in many sections, by hundreds of Māori at Maketu. The upper and lower ropes were of tightly-twisted leaves of tī kōuka, even stronger and more durable than flax! The floats on the top of the seine were made of whau, a very light wood. Rounded boulders in baskets acted as weights on the bottom. It caught 37,000 fish, the first time it was used!
Māori cooked and ate the tips of tī kōuka branches and produced high-sugar, energy-rich food by baking the roots, and sometimes the whole trunks, in deep earth ovens (umu) for days on end. Trampers will be keen to know that dead tī kōuka leaves make ideal fire-starters, and that strips from the leaves make strong, temporary boot-laces.
Cabbage tree decline
In the early 1980s, wilting and dying cabbage trees became common in Northland in disturbed, exposed habitats along highways, on farms, and in urban areas. This phenomenon peaked in the mid-1990s as the disease, caused by a bacterium carried by sap-sucking insects, spread as far as the northern South Island. The trees take three to twelve months to die, although some recover.