Tree of the month

MĀORI NAME: Kōwhai ENGLISH NAME: Large-leaved kōwhai BOTANICAL NAME: Sophora tetraptera

Kōwhai.

GROWING HABIT

Kowhai¯ grow up to 15m in height with spreading branches, so you’ll want to plan carefully before planting. Their distinctive yellow flowers will be on display between around September and December, and brown seedpods from October to May. Note that kowhai¯ is one of our few deciduous native trees, so be prepared for dropping leaves.

CARE & MAINTENANCE

They are fairly easy-care, being amenable to most kinds of soils. They enjoy the sun, but do take care with watering as they won’t take kindly to having wet roots for extended amounts of time.

Noticing defoliation on your kowhai?¯ Don’t worry, this is quite common and is caused by the caterpillar of the kowhai¯ moth. Research suggests the tree is pretty tolerant of this process and that the caterpillar populations are naturally kept in check by recurring disease.

HOW TO PROPAGATE

Now’s the time – before it gets any cooler. Kowhai’s¯ brown seedpods should still be easily located, and doing it this way is much easier than from cuttings.

Expose the seed by nicking with a knife or rubbing gently with sandpaper, then soak overnight to assist germination before planting into potting mix.

You should see signs of life in your punnet in two to four weeks, then your seedling will enjoy full sun and regular watering before planting in the ground in around two years.

IN THE WILD

Tetraptera has historically naturally occurred in the central and eastern North Island. However, it has since been extensively planted outside this region and has naturalised. Kowhai¯ is a primarily lowland scrub and forest species, also common around lake margins.

Kowhai¯ are a popular planting choice at New Zealand schools, as well as many parks, reserves and gardens.

Despite not being their original ecological district, Otago now backs the kowhai¯ with the DOC initiative Project Gold (featured in NZ Gardener’s

September 2020 issue), dedicated to gathering seeds and propagating kowhai¯ throughout the region – most notably including planting kowhai¯ along the length of the Central Rail Trail.

Because its bright yellow flowers drew the attention of the first visitors to New Zealand, kowhai¯ seed was taken to many places in the world. Seed was taken to Kew, and kowhai¯ was planted there from about 1772, with flowering trees recorded in London in 1779 and in Ireland in 1800.

USE IN RONGOĀ

Kowhai¯ is an important medicinal plant for M¯aori, who used bark-based teas to heal skin wounds, sprains and even broken bones. It’s important to note, though, that kowhai¯ wood is poisonous to humans, as it contains the toxin cytisine.

MĀORI & KŌWHAI

As those who remember the children’s song will know, kowhai¯ is te reo M¯aori for yellow. It’s said to symbolise personal growth, and helps people to move on from the past with a renewed sense of adventure.

Kowhai¯ also features in the whakatauk¯i (proverb), I hea koe I tea o o te kowhai,¯ which asks, “Where were you when the kowhai¯ was in bud?”. If the saying is addressed to you, you’ve skipped some timely duties and probably need to get to work!

EXPERT KNOWLEDGE

Northland Regional Advisor Paul Quinlan is based in Kaeo. He has over 20 years’ experience as a landscape architect and has particular expertise in indigenous forestry – from planting to harvesting of regenerating to¯tara on farmland. He also coordinates the Northland To¯tara Working Group and is a trustee of Ta¯ne’s Tree Trust.