Pittosporum tenuifolium: complete guide to Tawhiwhi

Overview

Pittosporum tenuifolium, better known as Tawhiwhi or Kohuhu, is a fascinating ornamental tree native to New Zealand. This tree naturally grows on both the North and South Islands of New Zealand, but is now introduced to many other countries including California, Great Britain, and Tasmania.

Tawhiwhi is an elegant, finely-built tree much used for screening, landscaping, and as a specimen tree in modern gardens. With its thin, fine foliage and elegant appearance, it's a perfect choice for gardeners wanting something graceful. This is a fascinating tree with much character.

Appearance & Bloom

Pittosporum tenuifolium grows as a medium to large tree, usually reaching 4 to 8 meters tall depending on region and growing conditions. The tree can grow even taller under optimal conditions. The tree has slender, upright growth and an elegant, symmetrical form.

The leaves are the most striking feature - very thin, very small, about 1 to 3 centimeters long. The leaves are glossy dark green, giving it a striking visual texture. Some cultivars have variegated foliage.

Flowers appear in spring (April-May) and are very small, inconspicuous flowers but highly fragrant - a fantastic fragrance in spring. The flowers are dark purple to almost black. After blooming, the tree forms interesting round seed capsules.

Ideal Location

Tawhiwhi performs best in locations receiving full to partial sun exposure. The tree tolerates partial shade well. At least four to six hours of sunlight daily is recommended. In partial shade, the foliage may be less glossy.

The tree is highly wind-tolerant, making it perfect for coastal areas and windy locations. This is a great advantage in many European gardens, especially coastal cities.

Soil

Tawhiwhi is not particularly fussy about soil type. The tree thrives in most soils, from sand to clay. However, well-draining soil is preferred. Avoid soil that is constantly waterlogged.

The tree tolerates acidic to neutral sandy loam well. A slightly acidic soil (pH 6.0 to 7.0) is suitable. You don't need to add much organic material - actually they grow better in somewhat poor soil.

Watering

Once established, Tawhiwhi is quite drought-tolerant. In the first season after planting, water regularly - about once weekly. Once the tree becomes well-rooted, you can water much less frequently.

From established trees, expect less water need. Water only during very dry periods. The tree tolerates drought well. In temperate climates, rainfall will usually be sufficient.

Pruning

Pruning is easy for this tree. Tawhiwhi responds well to pruning and can be shaped to your preference. For a more compact form you can prune regularly in spring and summer.

The tree can also be cut back hard if it becomes too large. It will easily regrow. For privacy screens you can use hedging techniques. Avoid pruning in late autumn or winter.

Maintenance Calendar

Spring (March-May): This is the best time for pruning. Prune in March for shape. Ensure regular water drainage.

Summer (June-August): Provide regular water during dry periods. You can light prune for maintenance and shape.

Fall (September-October): Gradually reduce pruning. Monitor for winter preparation.

Winter (November-February): Minimal work needed. The tree is semi-dormant. Protect against extreme weather.

Winter Hardiness

Pittosporum tenuifolium is winter hardy to about -5 to -10 degrees Celsius, depending on growing conditions. In Great Britain and southern Europe this is not a problem. In northern European regions, protection may be needed.

In very cold regions you can plant against walls or protect with burlap or fleece during hard frosts. Young material is more sensitive than mature plants.

Companion Plants

Tawhiwhi works well as a privacy screen or background plant in borders. It combines well with other Mediterranean or New Zealand plants. Phormium, Pittosporum crassifolium, and other similarly-natured shrubs work well.

The tree is also suitable for coastal gardens due to its wind-tolerance and salt-water tolerance.

Propagation

Pittosporum tenuifolium is propagated by seed or by cuttings, though cuttings are by far the more common method for the tree's many ornamental cultivars. Seed ripens in late summer (August-October) inside round seed capsules and can be sown fresh in a light, free-draining seed mix once the capsules split open. Germination takes three to six weeks at 18 to 21 degrees Celsius, though viability varies from batch to batch.

For well-known cultivars such as 'Tom Thumb' (a compact, purple-leaved form reaching about 1 meter), 'Silver Queen' (silvery variegated foliage), 'Purpureum' (deep purple leaves), and 'Golf Ball' (a naturally rounded, very compact form), cuttings are the only reliable way to preserve the ornamental traits. Take semi-ripe cuttings 10 to 15 centimeters long in July or August, strip the lower leaves, dip in rooting hormone, and insert into a mix of perlite and potting compost under plastic cover. At a soil temperature of 18 to 20 degrees Celsius, cuttings typically root within six to eight weeks.

Many garden centers, including Intratuin and Gamma in the Netherlands, stock both the species and popular cultivars in 2 to 10 liter pots, often already trained into small balls or standards ready for immediate planting.

Pests and Diseases

Pittosporum tenuifolium is generally quite trouble-free, though a handful of problems can occur, especially on stressed plants. Scale insects are the most common pest: small, brown, shield-shaped insects on the undersides of leaves and stems that secrete sticky honeydew. Treat with insecticidal soap or horticultural oil; light infestations can simply be pruned away.

Aphids may gather on young shoots in spring (April-May). A strong jet of water or natural predators such as ladybirds usually keep populations in check without chemical intervention.

The biggest threat is root rot from fungi such as Phytophthora in constantly wet, poorly drained soil. Symptoms include wilting foliage despite moist ground. Always ensure excellent drainage, especially for young plants during their first two growing seasons, and avoid overwatering during winter.

Conclusion

Pittosporum tenuifolium or Tawhiwhi is a very elegant and reliable tree for modern gardens. With its thin, fine foliage and slender form, it brings grace and structure to your garden. Provide a sunny to partially shady location, well-draining soil, and moderate water, and you'll have a low-maintenance tree lasting many years.

The tree is available at many garden centers in temperate European regions, including Intratuin and Gamma in the Netherlands. For landscaping ideas and combinations visit gardenworld.app. gardenworld.app also offers designs where this elegant New Zealand tree works perfectly.