Pittosporum crassifolium: complete guide to Karo

Overview

Pittosporum crassifolium, better known as Karo, is a fascinating evergreen shrub native to New Zealand. This plant naturally grows in the Kermadec Islands and northern New Zealand, but is now introduced to many other countries including Great Britain, California, and Tasmania.

Karo is a strong, reliable shrub useful for privacy screens, landscaping, and as a specimen plant. With its thick, leathery foliage and robust growth habit, it's a perfect plant for modern gardens. This is actually a very low-maintenance plant.

Appearance & Bloom

Pittosporum crassifolium grows as a medium to large shrub, usually reaching 3 to 6 meters tall depending on growing conditions. It can grow taller but easily prunes down. The plant has a dense, compact crown shape.

The leaves are very distinctive - thick, leathery, dark green, with characteristic silvery undersides. This gives the plant its English name "stiffleaf cheesewood". The leaves are approximately 5 to 10 centimeters long.

Flowers appear in spring (April-May) and are small, inconspicuous dark-red or brown tubular flowers. The flowers aren't spectacular but provide the plant with a pleasant fragrance. Flowers attract pollinators. After blooming, the plant forms interesting bird-attracting seed capsules.

Ideal Location

Karo performs best in locations receiving full to partial sun exposure. The plant tolerates partial shade well, although growth may be somewhat slower. At least four to six hours of sunlight daily is ideal.

The plant is highly wind-tolerant, making it perfect for coastal areas and windy locations. This is actually an advantage in many European gardens.

Soil

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

The plant tolerates acidic to neutral sandy loam well. You don't need to add much organic material - actually they grow better in somewhat poor soil. A pH range of 6.0 to 7.5 is suitable.

Watering

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

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

Pruning

Pruning is easy for this plant. Karo 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 plant 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 plant is dormant. Protect against extreme weather.

Winter Hardiness

Pittosporum crassifolium is winter hardy to about -8 to -12 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.

Companion Plants

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

The plant is also suitable for coastal gardens due to its wind-tolerance.

Propagation

Pittosporum crassifolium can be propagated by two methods: seed or cuttings. Seed is collected in late summer to early fall (August-October) once the seed capsules split open, revealing the sticky, resinous seeds inside. Sow fresh seed in a tray filled with a light, free-draining seed mix. Germination typically takes three to six weeks at temperatures between 18 and 21 degrees Celsius. Seedlings grow slowly during their first year and benefit from a sheltered spot.

Cuttings are the faster, more reliable method for home gardeners. Take semi-ripe cuttings about 10 to 15 centimeters long in July or August, ideally from non-flowering side shoots. Strip the lower leaves, dip the cut end in rooting hormone, and insert the cutting into a mix of perlite and potting compost. Keep cuttings under plastic or in a heated propagator to maintain high humidity. At a soil temperature of 18 to 20 degrees Celsius, cuttings typically root within six to eight weeks.

The compact selection 'Compactum', a popular nursery form valued for its denser, lower growth of roughly 1.5 to 2 meters, is propagated exclusively by cuttings, since seedlings won't reliably inherit the compact trait. Many garden centers, including Intratuin and Gamma in the Netherlands, stock pre-grown specimens of both the straight species and 'Compactum' in 3 to 10 liter pots.

Pests and Diseases

Pittosporum crassifolium is generally quite trouble-free compared to many other garden shrubs, which contributes to its reputation as a low-maintenance species. Still, a handful of problems can appear, particularly on plants stressed by drought or poor air circulation.

Scale insects are the most common pest: small, brown, shield-shaped insects that attach themselves to the undersides of leaves and stems, secreting sticky honeydew that can attract sooty mold. Treat with insecticidal soap, a horticultural oil spray, or simply prune away lightly affected twigs.

Aphids can gather on young shoots and flower buds in spring (April-May). A strong jet of water dislodges most colonies; for persistent problems, a soap solution helps. Beneficial insects such as ladybirds and hoverflies naturally keep aphid populations in check if you avoid chemical treatments.

The biggest threat remains root rot, caused by fungi such as Phytophthora in constantly wet, poorly drained soil. Symptoms include wilting foliage despite moist ground and a dark, soft patch at the base of the stem. Prevention is the only effective approach: ensure excellent drainage and avoid overwatering, especially during winter months.

Conclusion

Pittosporum crassifolium or Karo is a very practical and reliable shrub for modern gardens. With its thick foliage and dense growth, it brings structure and privacy screens to your garden. Provide a sunny to partially shady location, well-draining soil, and moderate water, and you'll have a low-maintenance plant lasting many years.

The plant 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 strong New Zealand plant works perfectly.