Ngaio

Family

Myoporaceae

Habit

Shrub

Height

6 m

Spread

3 m

Growth

very fast

Lifespan

44 years

First yield

after 2 years

Hardiness

zone 10–12

Shade tolerance

light shade

Soil

Sand, Silt, Loam

Soil moisture

very dry – moist

pH

5.5 – 8

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Edible: Ngaio is not a food plant, and the widespread claim that its fruit can be made into jam or jelly is misleading. The small red-purple drupes were occasionally used as a traditional food in New Zealand, but the plant contains the liver toxin ngaione, and consumption is expressly not recommended. The toxin sits above all in the leaves and causes severe liver damage in grazing animals; for humans the evidence is thin, and that is precisely why caution is called for. Anyone planting it should plan it in as an ornamental, hedge and shelter plant and not as a source of fruit. The berries are best left to the birds, which eat and disperse them in its home range without apparent harm.

Medicinal: In traditional Māori medicine of New Zealand, extracts from the plant were used to treat various complaints, such as: dentistry, wound healing. The bark is used to treat ulcers.

Other uses: The practical value of ngaio lies in its toughness. As a fast-growing, evergreen, salt-spray-proof tree it is the standard plant for shelter belts, screening and hedging in coastal regions, and it is used to stabilise banks and dunes where little else will grow. As an ornamental it is valued for its dense habit, the glossy leaves with their translucent oil glands and the spotted flowers. Boiling the leaves yields a decoction traditionally applied to the skin as a mosquito repellent — the essential oils responsible are the same ones that make the plant poisonous to grazing animals. The wood is tough and durable and was used in New Zealand for tools and small implements.

Site: In Central Europe ngaio is a container plant needing bright, frost-free winter quarters; planted out it is an option only in frost-free coastal climates. Where that applies it is hard to beat: fast-growing, evergreen, wind- and salt-tolerant, and thus the classic front rank of a coastal hedge. One point decides everything else, though: its leaves contain the liver toxin ngaione, which causes severe and often fatal poisoning in horses, cattle, sheep and pigs. It therefore has no place at all beside pasture, paddocks or small livestock pens, and the prunings must not end up there either, since wilted foliage is eaten more readily than fresh. In California it has become invasive, so fruit set and seedlings are worth watching. Care: It grows fast and takes pruning well, so hedges and shapes are easy to hold; cut after winter and dispose of the prunings safely rather than composting them where grazing animals have access. Once established it needs little water, and feed sparingly — generous feeding produces soft, brittle growth. In a container it wants a free-draining medium and, in winter, a bright position a few degrees above freezing with very restrained watering. One serious pest is the myoporum thrips, which has killed off whole plantings in California since the mid-2000s; it causes thickened, distorted shoot tips that should be cut out generously.

Ngaio is straightforward to propagate. The small red-purple drupes ripen in summer; the flesh is removed and the stones sown fresh into free-draining, evenly moist medium, where they come up at twenty degrees without special pre-treatment. The seedlings grow briskly and reach a respectable height in the first year. Faster and true to type are half-ripe cuttings taken from the current year's shoots in late summer and rooted under a cover with gentle bottom heat; rooting is reliable and needs no hormone. Since growth is rapid anyway, it pays to cut young plants back hard once so that they branch from the base — for hedging use this is the decisive step. When handling prunings, remember that the leaves are toxic.

For Central Europe the wildlife value of ngaio is negligible: here it stands in a container, is not meshed with the native fauna and serves no local species as a larval food plant. In its home range the picture differs. From mid-spring into high summer it carries numerous small white flowers spotted with purple, which insects visit, followed by red-purple drupes dispersed by birds — the same route by which it has reached the open landscape in California. Its greatest contribution is structural: as a densely leaved, evergreen, wind-firm coastal tree it offers cover, nesting opportunity and wind shadow in an exposed zone where little else grows, and under that shelter more sensitive species can establish. The toxicity of the leaves concerns grazing livestock, not the wild fauna.

Special features: leaves held against the light show translucent oil glands as pale dots; Maori name ngaio, with related words running right across the Polynesian languages; tradition holds that the Maori saw a ngaio tree in the markings of the moon; the same oil that served as a mosquito repellent makes it poisonous to livestock; killed off across large areas of California by the myoporum thrips since the 2000s.

New Zealand: ngaio is endemic to the New Zealand islands, where it is above all a tree of the coast and the coastal lowland, including the Chatham Islands. Its natural range is therefore a comparatively small area in the South Pacific. As a tough, fast-growing and salt-tolerant coastal plant, however, it has been carried far: introduced, it now occurs in Portugal, South Africa and Namibia, as well as around the Mediterranean and in California, where it was planted as a street and hedging tree. In California it has escaped cultivation and is listed by the state's invasive plant body as an invasive exotic. In Central Europe it is not hardy and appears only as a container plant.

Ngaio grows in the coastal and lowland forests of New Zealand, sometimes in pure stands and sometimes in association with other species such as the nikau palm. Its place is the wind-exposed, salt-sprayed coastal belt, which it handles with leathery, thick-fleshed leaves and rapid growth; it wants full sun and takes almost any soil as long as it drains. As an evergreen tree it reaches up to ten metres with a crown about four metres across and a trunk around thirty centimetres thick; young plants are dome-shaped, while with age the branches twist picturesquely. Characteristic are the translucent oil glands in the leaves, visible as pale dots against the light. Frost sets its limit: a Central European winter outdoors is beyond it.