Pittosporum tenuifolium
Pittosporum tenuifolium
Pittosporum tenuifolium, also known as kōhūhū, is a native New Zealand shrub or small tree with wavy-edged leaves and dark stems. It is popular for hedging and shelter, and produces small, fragrant dark flowers in spring. Growing up to 10 meters tall, this versatile native is prized for its elegant form, wavy-edged leaves with contrasting light midribs, and distinctive dark purple-black flowers that release a sweet honey scent in the evening. With its compact growth habit and ability to thrive in a range of conditions, Kōhūhū has become a popular choice for hedging, specimen planting, and ecological restoration throughout New Zealand and internationally. native trees
Image credit: Kōhūhū (Pittosporum tenuifolium). Wikipedia
Quick Facts
| Scientific Name | Pittosporum tenuifolium |
|---|---|
| Height | Up to 10 m (usually 4–8 m in gardens) |
| Spread | 2–4 m (bushy, upright habit) |
| Water Needs | Low to moderate; drought-tolerant once established |
| Light | Full sun to partial shade |
| Frost Tolerance | Moderate (tolerates light to moderate frost) |
| Salt Tolerance | Moderate (tolerates some coastal exposure) |
| Growth Rate | Fast |
| Lifespan | Long-lived (decades) |
Climate Best Suited To
Kōhūhū (Pittosporum tenuifolium) is well-distributed throughout New Zealand, being absent only to the west of the Southern Alps and Stewart Island. It naturally occurs in coastal and lower mountain forest areas up to an altitude of 900m. The species thrives in a wide range of conditions but prefers areas with good drainage and moderate rainfall. It is particularly common at forest edges and in disturbed areas, playing an important role in ecological succession.
Regional Suitability
| City | Climate Suitability |
|---|---|
| Whangārei | Ideal |
| Auckland | Ideal |
| Hamilton | Ideal |
| Tauranga | Ideal |
| Rotorua | Ideal |
| Gisborne | Ideal |
| New Plymouth | Ideal |
| Napier | Ideal |
| Whanganui | Ideal |
| Palmerston North | Ideal |
| Wellington | Ideal |
| Nelson | Ideal |
| Christchurch | Ideal |
| Dunedin | Ideal |
| Invercargill | Moderate |
| Queenstown | Moderate |
Growing
- Thrives in well-drained soil
- Prefers full sun to partial shade
- Tolerates wind and light frost
- Water regularly during establishment
Uses
- Popular as a hedge or screening plant
- Ornamental specimen for gardens and landscaping
- Attracts birds and insects with its flowers and fruit
- Traditional Māori uses include medicinal applications
Seasonal Care
- Spring: Prune to shape and encourage new growth
- Summer: Water during dry spells; monitor for pests
- Autumn: Mulch and tidy fallen leaves
- Winter: Protect young plants from heavy frost
Pruning
- Prune after flowering to maintain shape and size
- Remove dead or damaged branches as needed
Planting Guide
- Choose a sunny or partially shaded site with good drainage
- Dig a hole twice the width of the root ball
- Mix compost into the soil
- Plant at the same depth as in the nursery container
- Water well and mulch around the base
Propagation
Kōhūhū can be propagated by several methods:
From Seed
Seed propagation is relatively straightforward but may be slow:
- Collect ripe seed capsules when they turn black and begin to split (January to March)
- Remove the sticky substance coating the seeds (this acts as a germination inhibitor)
- Sow in a seed-raising mix and cover lightly
- Keep moist but not wet
- Germination can take 4-8 weeks or longer
- Seedlings may have unusual characteristics, with some having three or four seed leaves instead of the usual two
From Cuttings
Semi-hardwood cuttings provide the most reliable method:
- Take 10-15cm cuttings from semi-hardwood growth in late summer or autumn
- Remove lower leaves and dip in rooting hormone
- Plant in a free-draining propagation mix
- Keep humid but not wet
- Rooting should occur within 6-8 weeks
Cultural History
Pittosporum tenuifolium has significant cultural importance in New Zealand:
Traditional Māori Knowledge
- Known by several Māori names including Kōhūhū, Kohukohu, Tawhiwhi, and Rautāwhiri
- The name "Rautāwhiri" (meaning "to wave a leaf") reflects its use in ceremonies
- The resin and oils extracted from leaves were used for their scent
- Scented oils were used to perfume little pouches or bird skins worn around the neck
- The oil was also used to scent houses and mats of people of high rank
Medicinal Uses
- The resin was mixed with other gums and chewed as a cure for bad breath and mouth sores
- Parts of the plant were used as topical treatment for skin diseases
- Crushed leaves were used as a poultice for ulcers
- Crushed bark soaked in water was used to treat breast or chest ailments
- Used together with flax root to make a brew for treating fever, bleeding, and bruising
- Modern research has confirmed some antimicrobial properties
Ceremonial Significance
- Branches were used in Māori life ceremonies, such as baptisms
- Used for welcoming visitors to a marae
- The common names "tāwhiri" (to wave to) and "rautāwhiri" (to wave a leaf) reflect this ceremonial use
European Settlement Impact
- Recognized early for its ornamental potential
- Widely cultivated both in New Zealand and internationally
- Several cultivars have been developed for ornamental horticulture
- Multiple varieties have won the Royal Horticultural Society's Award of Garden Merit
Contemporary Significance
Today, Kōhūhū is valued for both its ecological role and ornamental qualities. It is extensively used in landscaping, as hedging, and in ecological restoration projects. Its ability to thrive in a range of conditions makes it a versatile choice for gardens throughout New Zealand. The species continues to gain popularity internationally, particularly in temperate regions where its distinctive foliage and adaptability are highly valued.
Pests & Diseases
Common Pests
- Pittosporum Flower Weevil (Aneuma rubricale): A native insect that lays eggs on flowers and larvae feed on stamens and ovaries.
- Scale Insects: Can infest stems and leaves. Control with horticultural oil or insecticidal soap.
- Pittosporum Shield Bug (Monteithiella humeralis): Feeds on sap. Control with insecticidal soap if infestation is severe.
- Pittosporum Psyllid (Trioza vitreoradiata): Feeds on sap and leaves characteristic "beads" behind.
- Thrips: May cause stippling on leaves. Control with insecticidal soap.
Common Diseases
- Root Rot: Caused by overwatering or poor drainage. Ensure well-draining soil.
- Leaf Spot: Various fungi can cause spotting on leaves. Remove affected foliage and improve air circulation.
- Sooty Mold: Black fungal growth on leaves, often following insect infestations.
- Elsinoe takoropuku: A recently discovered fungus that causes swelling of twigs.
- Pythium irregulare: Can cause foliar blight and rot.
Environmental Issues
- Frost Damage: Young plants and new growth can be damaged by severe frosts.
- Waterlogging: Despite drought tolerance, cannot withstand constantly wet soil.
- Nutrient Deficiency: Yellowing leaves may indicate lack of nutrients.
Kōhūhū is generally resilient to pests and diseases when grown in appropriate conditions. Its natural adaptations make it one of the more trouble-free native plants. Most issues can be prevented by providing good drainage and appropriate light levels.
Bonus Tip
Create a stunning native hedge by combining different Pittosporum cultivars for a tapestry of colors and textures. Plant the standard green Kōhūhū alongside purple-leaved cultivars like 'Nigricans' and variegated forms such as 'Silver Queen' or 'Irene Paterson'. Space plants 60-80cm apart and trim regularly to encourage dense growth. This mixed hedge not only provides year-round interest but also creates a more resilient planting that's less susceptible to pest and disease outbreaks than a single-variety hedge. For an even more diverse ecosystem, underplant with native ground covers like Acaena inermis or Muehlenbeckia axillaris to suppress weeds and provide habitat for beneficial insects. The evening fragrance of Kōhūhū flowers will attract night-flying moths, contributing to your garden's biodiversity.
