T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Sophora microphylla (Kowhai)

Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Fabales
Family: Fabaceae
Subfamily: Faboideae
Genus: Sophora  (eight species)
Species: S.microphylla
Scientific name: Sophora microphylla
Synonyms: Edwardsia microphylla, Edwardsia grandiflora var. microphylla, Sophora tetraptera var. microphylla. 
Common name: Kowhai ( kowhai is the Maori word for yellow)

 Parts of this tree is poisonous, See text below.

Sophora microphylla is woody legume medium to large tree in the genus Sophora and is native to New Zealand. It is the most common of the eight species.   It is endemic throughout the main islands of New Zealand but scarce in parts of Northland. In the wild It is also scarce to absent over large parts of the eastern North Island from about East Cape south to the northern Wairarapa.  Sophora microphylla trees are now grow throughout the country and are a common feature in New Zealand gardens. It is our  national flower.
Sophora microphylla has smaller leaves (5–7 mm long by 3–4 mm wide) and flowers (2.5-3.5 cm long) than S. tetraptera which has leaves of 1–2 cm long and flowers that are 3 cm-5 cm long and appear August -October.  
The very distinctive, almost segmented pods, which appear after flowering each contain six or more smooth, hard, yellow seeds. These seeds can be very numerous and the presence of many hundreds of these distinctively yellow seeds on the ground quickly identifies the presence of a nearby Kowhai tree. Many other Kowhai trees lose most of their leaves immediately after flowering in October or November but quickly produce new leaves. The native pigeon gorge themselves on both the flowers and the leaves. They can kill a tree with their constant nibbling.

Te ngahere-forest lore: When the bright yellow flowers of kowhai bloom, in late winter and early spring, it is time to plant kumara (sweet potato). Pigment for yellow dye was extracted from the flowers, and the flexible branches were good for making houses and bird snares.

All parts of the plant but especially the ripe yellow seed are poisonous. Because the seed are hard they will take a lot of chewing to cause harm. If the seed are crushed before eating it is more likely that they will cause harm. The major toxin is Cytisine and symptoms of poisoning include nausea, vomiting, increased heart rate, twitching of muscles or loss of coordination. Onset of these symptoms may occur within one hour. In extreme cases symptoms include paralysis and respiratory failure.

Sophora microphylla is  the only member of the genus that has a distinct juvenile form. In this form it is a small leaved divarcating shrub. This form can exist for many years and can take 10 years to flower.

Juvenile form of Sophora microphylla growing at Pukekura Park, New Plymouth


 

Top surface of juvenile leaf.

Underside of the juvenile leaf.

A  large Sophora microphylla growing at the Rown street entance to Pukekura Park. September. Click to enlarge
 

A Tui and the Wood pigeon feeding on this tree
 
Sophora microphyllai seeds and the seed pod



Sophora microphylla hybidises with all the other species except S. molloyi.
Photo below is hybrid.  Note it is  flowering while it has its leaves.


A cultivar of Sophora microphylla