Kà Âwhai ( or ) are small woody legume trees within the genus Sophora, in the family Fabaceae, that are native to New Zealand. There are eight species, with Sophora microphylla and Sophora tetraptera being large trees. Their natural habitat is beside streams and on the edges of forest, in lowland or mountain open areas. Kà Âwhai trees grow throughout the country and are a common feature in New Zealand gardens. Outside of New Zealand, kà Âwhai tend to be restricted to mild temperate maritime climates. The blooms of the kà Âwhai are widely regarded as being one of New Zealand's unofficial national flowers.
The MÃÂori word kà Âwhai derives from the Proto-East Central Pacific word kà Âfai, used to refer to leguminous trees that grow pods and typically have distinct flowers. It is related to words in some other Polynesian languages that refer to different species that look superficially similar, such as (Sesbania tomentosa), (Sesbania grandiflora) and Marquesan kohai (Caesalpinia pulcherrima). Kà Âwhai is also the MÃÂori word for the colour yellow. This is unique to MÃÂori, as many other Polynesian languages use a word derived from Proto-Eastern Polynesian rega-rega, such as and , and may represent the word for the flower replacing the older word. The spelling kowhai (without a macron) is common in New Zealand English.
KÃ Âwhai is a name that can be used to describe any of the eight currently known species of Sophora that is native to New Zealand, of which the most commonly found species are Sophora microphylla and Sophora tetraptera. While all are members of the same genus, they do not form a clade. Sophora microphylla, for example, is more closely related to Sophora toromiro, an endemic species from Easter Island / Rapa Nui, than to Sophora prostrata. Sophora cassioides, found in Chile, may represent a species that spread to South America from New Zealand. Sophora is one of the four genera of native legumes in New Zealand; the other three are Carmichaelia, Clianthus, and Montigena.
Taxonomy of the New Zealand Sophora species is a complex issue due to shared morphological features, hybrids that can form between species, differences in juvenile stages of plants based on geography, and morphological features being inconsistent with genetic profiles. Sophora microphylla that grow in the southern and eastern South Island have variable and persistent juvenile forms, something not seen in plants that found in the North Island, potentially due to gene transfer from other kà Âwhai species. Three major species complexes exist in New Zealand that facilitate gene transfer. In the North Island, Sophora microphylla, Sophora chathamica, Sophora fulvida, Sophora godleyi and Sophora tetraptera can form hybrids, while Sophora microphylla, Sophora longicarinata and Sophora prostrata can hybridise in the South Island. Additionally, Sophora tetraptera, Sophora molloyi and Sophora godleyi can also form hybrids. As many species thrive in specific environments, hybrid forms may often struggle to persist in the wild, though areas with persistent hybrid forms of plants persist. Due to this hybridisation, specific species names can often be difficult to assign to individual plants.
The eight currently accepted species of kà Âwhai are:
Most species of kà Âwhai grow to around high and have fairly smooth bark with small leaves. Sophora microphylla has smaller leaves ( long by wide) and flowers ( long) than Sophora tetraptera, which has leaves of long and flowers that are long.
The very distinctive seed pods that appear after flowering are almost segmented, and each contains six or more smooth, hard seeds. Most species have yellow seeds, but Sophora prostrata has black ones. The seeds of Sophora microphylla 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 kà Âwhai tree. Many species of kà Âwhai are semi-deciduous and lose most of their leaves immediately after flowering in October or November, but quickly produce new leaves. Flowering of kà Âwhai is staggered from July through to November, meaning each tree will get attention from birds such as tà «Ã«, kererà « and bellbird. The specific form and yellow petals of most kà Âwhai found in New Zealand is likely an adaptation to bird pollination from tà «Ã« and bellbirds. Tà «Ã« are very attracted to kà Âwhai and will fly long distances to get a sip of its nectar.
The wood of kà Âwhai is dense and strong, and has been used in the past for tools and machinery.
Studies of accumulated dried vegetation in the pre-human mid-late Holocene period suggests a low Sophora microphylla forest ecosystem in Central Otago that was used and perhaps maintained by giant moa birds, for both nesting material and food. The forests and moa no longer existed when European settlers came to the area in the 1850s.
Kà Âwhai can be grown from seed or tip cuttings in spring and autumn. The dark or bright yellow seeds germinate best after chitting and being soaked in water for several hours. They can also benefit from a several minute submersion in boiling water to soften the hard shell and then being kept in the same water, taken off boil, for several hours to soak up the water. Young kà Âwhai are quite frost tender, so cuttings or seedlings should be planted in their second year when they are 30 cm or higher.
If grown from seed, kà Âwhai can take many years to flower, the number of years varies depending on the species.
Sophora prostrata, sometimes called "little baby", is used as a bonsai tree. It grows up to high, has divaricating stems, and sparse smallish leaves.
All parts of the kà Âwhai, particularly the seeds, are poisonous to humans, due to the presence of cytisine. However, there do not appear to have been any confirmed cases in humans of severe poisoning following ingestion of kà Âwhai in New Zealand. Some reports exist of people becoming ill after using cutlery made from kà Âwhai wood, or from consuming kererà « that had fed on the plant.
Traditionally the MÃÂori used the flexible branches as a construction material in their houses and to snare birds. The kà Âwhai flowers were a source of yellow dye. The blooming of kà Âwhai flowers late winter and early spring was used as a seasonal indicator as a time to plant kà «mara (sweet potato), and to begin harvesting kina (sea urchins).
Kà Âwhai are an important tree for rongoà(traditional medicine practices) for many iwi, particularly bark used to create an infusion known as wai kà Âwhai. The bark was heated in a calabash with hot stones, and made into a poultice to treat wounds or rubbed on a sore back or made into an infusion to treat bruising or muscular pains. If someone was bitten by a seal, an infusion was prepared from kà Âwhai and applied to the wounds and the patient was said to recover within days.
Additionally, wedges made of kà Âwhai stem were used to split wood, it was used for fences and in whare (MÃÂori hut) construction, implements and weapons.
The currently dispersal of kà Âwhai around New Zealand likely represents deliberate plantings by MÃÂori, such as Te ÃÂti Awa bringing Taranaki species of kà Âwhai to Wellington when some members of the iwi migrated to the area.
KÃ Âwhai's distinct yellow flowers are common in New Zealand-related iconography, and have been depicted on stamps and coins, are widely regarded as being one of New Zealand's unofficial national flowers. As such, it is often incorporated as a visual shorthand for the country, such as in Meghan Markle's wedding veil, which included distinctive flora representing all Commonwealth nations.