Kowhai

Kowhai, the national flower of New Zealand, is as loved by the Kiwis as our indigenous wattle is loved by Aussies. It is interesting that they both flower in spring, both are in the pea family Fabaceae and both have yellow flowers. Kowhai is apparently the Maori word for yellow and refers in the main to Sophora tetraptera, although there are several species in the genus that go by the common name. The genus itself has between 50 and 80 species (depending which reference you read) occurring worldwide. At present botanists have decided 8 are endemic to New Zealand and the three commonest species referred to as kowhai are S. tetraptera, S. microphylla andS. prostrata.

credit

The kowhai is a great small tree that is widely planted in NZ but rarely seen in Australia. It has small pinnate leaves that hang elegantly from the branches and make a delightful tracery against the sky. S. tetraptera has larger leaflets and flowers than S. microphylla and grows to between 4.5m and 6m tall. It is sometimes referred to as the North Island kowhai. S. microphylla occurs on both North and South Islands and tends to have smaller leaves and flowers and often goes through a prolonged juvenile stage (10 – 17 years) before flowering. It eventually forms a tree to between 6 and 9m tall. A hallmark of this juvenile stage is marked divarication of the entire plant. Divarication is when the stems grow in a zig-zag manner resulting in quite a tangle! As a rule of thumb S. microphylla is usually more cold tolerant than S. tetraptera. Most of the NZ sophoras are semi deciduous although this varies between species and from location to location.

The flowers of the kowhai are often described as being horn-shaped with the stamens protruding from the end. They hang in bunches from the branches often appearing before the leaves and come in all shades of yellow – almost to orange in some forms. In NZ the flowers are loved by the nectar feeding tuis, bellbirds and kereru (a type of pigeon). In my garden, the wattle-birds and honeyeaters fight over the rights to hang upside down to feed from the flowers which appear for about four weeks.

In New Zealand there are many cultivars of S. microphylla available on the market. Cultivars such as 'Dragon's Gold', 'Earlygold', 'Goldie's Mantle' and 'Te Atatu Gold' with various characteristics such as prolonged flowering, good flower colour or improved form. These are vegetatively propagated whereas all of the trees grown for revegetation projects are seed grown. Like our acacias, the seed of the kowhai benefits from hot water treatment before sowing.

source

S. prostrata is as its species name implies, a small low plant. It grows as a tangled wiry shrub from 1.5m to 2.4m. Flowers are not produced profusely and tend to be hidden in the centre of the bush. There is one cultivar called 'Little Baby' which grows to about 1.5m tall.

The kowhai is found from sea level to mountain districts in its Kiwi home and grows in forests, on open hillsides and along rivers. They are very easy to grow and will cope in almost any soil and any situation. My 10 year old specimen is, at the end of September, currently covered with flowers and has reached a height of about 4m growing in poor hydrophobic soil piled on top of lumps of concrete!

The plant formerly known as S. tetraptera 'Gnome' has now been identified as originating from Lord Howe Island and is now to be called S. howinsula 'Gnome'. Another interesting sophora story concerns S. toromiro which comes from Easter Island (Rapa Nui) and is closely related to the New Zealand sophoras. It used to be found all over the island before the island was totally denuded. There is now a worldwide program to search for and propagate from any plants originating from Easter Island, in order to commence the revegetation of the island. Interestingly most of the plants have been discovered in botanic gardens around the world, where each plant's provenance (where it came from) is always carefully recorded. They even discovered a healthy S. toromiro in our own botanic gardens in Melbourne!

A last word on pronunciation. Kowhai is widely pronounced 'ko-eye' but being a Maori word is supposed to be pronounced 'corfai' so you may hear both words used. This is one of those cases where it pays to know the Latin name!

REFERENCES: New Zealand Trees and Shrubs by L.J. Metcalf, Reed https://en.wikipedia.org/wiki/K%C5%8Dwhai