Kōwhai

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Kōwhai are small to medium native trees from New Zealand. They belong to the Sophora group in the bean family, and there are eight species. The best known large kōwhai trees are Sophora microphylla and Sophora tetraptera. They grow along streams and forest edges, in lowland and mountain areas, and you’ll find them across the country. They are also common in New Zealand gardens. Outside New Zealand, kōwhai do best in mild, temperate climates.

The bright yellow flowers are famous and are often called New Zealand’s unofficial national flower. The Māori word kōwhai comes from kōfai, a term for leguminous trees with pods and showy flowers. Kōwhai also means the color yellow.

Taxonomy is tricky for kōwhai. There are hybrids between species, and juvenile forms can look different depending on where they grow, so scientists sometimes have trouble naming individual plants. The eight accepted species include, among others, Sophora microphylla, Sophora tetraptera, Sophora chathamica, Sophora fulvida, Sophora godleyi, Sophora longicarinata, Sophora prostrata, and Sophora molloyi.

Most kōwhai trees grow about 8 meters high. They usually have smooth bark and small leaves. Sophora microphylla has smaller leaves and shorter flowers than Sophora tetraptera. After flowering, they form distinctive seed pods with six or more seeds. Most seeds are yellow, but Sophora prostrata has black seeds.

Kōwhai flowers from July to November, often in a staggered way so birds like tūī, kererū, and bellbirds visit for nectar. The yellow flowers are thought to help attract these birds for pollination. The wood is dense and strong and was historically used for tools and machinery.

Kōwhai can be grown from seed or from tip cuttings in spring or autumn. Seeds germinate best after soaking and a little scarification; some people briefly boil the seeds to help them sprout. Young kōwhai are sensitive to frost, so planting should wait until they are about 30 cm tall in their second year. If grown from seed, it may take several years before the plant flowers.

Sophora prostrata, also called “little baby,” is sometimes kept as a bonsai. All parts of kōwhai, especially the seeds, are poisonous to humans because of cytisine. There are very few reported cases of people being seriously poisoned by eating kōwhai, but some people have fallen ill after eating seeds or after kererū that fed on kōwhai were eaten.

For Māori, kōwhai served many uses. The flexible branches were used in building and snares, the bark was used to make wai kōwhai (an infusion used as a poultice for wounds or sore muscles), and the bright flowers provided a yellow dye. Kōwhai flowering in late winter and early spring also helped mark when to plant kūmara (sweet potato) and begin harvesting kina (sea urchins). Today kōwhai remains a valued symbol in New Zealand, often appearing in stamps, coins, and other imagery as a representation of the country.