Sophora microphylla Aiton

Nomenclature and Basic Classification

Sophora microphylla, commonly known as weeping kōwhai, small-leaved kōwhai, and sometimes South Island kōwhai, is a species of flowering tree in the Fabaceae family, native to New Zealand. This name South Island kōwhai is misleading, as the species is widely distributed across New Zealand’s main islands. It is the most widespread of the eight recognized New Zealand kōwhai (New Zealand Sophora) species.

Mature Size

It grows as an evergreen shrub or small tree reaching 8 meters (26 feet) in both height and width.

Leaf Features

Each leaf grows to 10 cm (4 in) long, and holds up to 40 pairs of shiny oval leaflets. Its leaflets typically measure 3–6 mm long by 2–5 mm wide, smaller than the leaflets of the well-known related species Sophora tetraptera (large-leaved kōwhai); its flowers also measure 1.8–5.0 cm long, smaller than those of S. tetraptera.

Etymology of Epithet

The specific epithet microphylla translates to 'small-leaved', referencing this trait.

Juvenile Growth Form

Young S. microphylla plants have a divaricating, bushy growth form with many interlacing branches; this characteristic habit gradually disappears as the tree matures.

Native Distribution

While S. microphylla occurs throughout all of New Zealand’s main islands, it is scarce in parts of Northland and in parts of the eastern North Island, ranging from East Cape south to northern Wairarapa.

Cultivar Recognition

The cultivar Sun King 'Hilsop' has received the Royal Horticultural Society's Award of Garden Merit.

Host Species Role

In ecological terms, S. microphylla is one of only three known native New Zealand species that act as a host for the native longhorn beetle Coptomma variegatum.

Nectar Toxicity

The nectar of this plant is toxic to honeybees.