Pepper tree is a common name for two distinctly different native trees – horopito and kawakawa. Horopito has peppery tasting leaves and belongs to a primitive flowering family – the Winteraceae. Kawakawa has heart-shaped leaves and belongs to the Piperaceae family, which is the true pepper family. Kawakawa is closely related to the Polynesian kava plant.
Horopito (Pseudowintera colorata) is a shrub or small tree that grows to eight metres in height. It grows throughout much of New Zealand, with the exception of the far north. It is abundant in upland and mountain forests in the North Island, and extends down to sea level in the southern South Island. It regenerates well after the destruction of tall forests and at high altitudes forms dense secondary shrublands and low forest.
The upper surface of its light green, elliptical leaves is splotched with red, especially if the plant is exposed to the light. The underside is blue-grey. Tiny greenish-white flowers appear in early spring, followed by black berries in autumn.
Horopito leaves have a hot peppery taste and leave a burning sensation in the mouth. The taste is caused by polygodial, a compound that also has some anti-fungal properties. As horopito tastes bad to deer and stock, it often dominates understorey vegetation in heavily browsed forests.
Lowland horopito (P. axillaris) grows to about 10 metres in height. It is common in forests of the North Island up to about 700 metres and lowland forests in the northern half of the South Island. It has glossy green leaves, slightly larger than those of its upland relative. Like horopito, it flowers in early spring, producing tiny lime-coloured flowers along its branches. Its fruit is a dark red berry.
Kawakawa (Macropiper excelsum) is found in coastal and lowland forests throughout the North Island and the northern half of the South Island. It is a small tree, growing to six metres tall, with dense branches. It is easily recognised by its heart-shaped leaves and jointed stems, which resemble bamboo stalks. The leaves are often pocked with holes caused by the looper caterpillar Cleora scriptaria.
The tiny male and female flowers are arranged in upright spikes and grow on separate trees. In summer female spikes ripen to a deep orange and their swollen fruits are a favoured food of forest birds.
Kawakawa was often used by Māori. The leaves were placed over cuts and boils to speed up healing, and a tea was made from an infusion of its leaves.